More from NeuroLogica Blog
Solar power as a source of electricity has been on a meteoric rise, and has crossed some encouraging milestone recently. Every way you look at it, solar is booming. This is driven primarily by the decrease in the cost of adding solar power, so let’s start there. The Berkley Lab has been tracking the cost of solar power in the US for years, so they are a reliable source of information. They get direct data from the actual price paid by consumers, and break down the cost of panels, the cost of installation, and all the “soft” costs that are part of the industry. In 2009 the total cost of installing solar between $7 – 8.70 per watt. An average US residential home installs a 6-8 kW system, with the average increasing over the years. In 2025 the average size was 7.7 kW. Let’s use a 7 kW system, at $8 per watt, that’s $56,000 total installation cost. Today the average price of installed residential solar in the US is $3.6 per watt (but it is $3.0 if you pay upfront, $4.50 if you finance). So that same 7 kW system now costs $25,200. (If you pay for it outright, the cost drops to $21,000.) So over the last two decades the total const of installed residential solar has dropped by about 60%. This is without considering any tax breaks or incentives. The reason for the decrease is partly that solar panels themselves are cheaper, and they are more efficient, so a 7kW system requires fewer panels. Installation costs have decreased by about 50% over this time, largely due to economies of scale. However, the US still has higher soft costs for solar than many other industrialized nations, and this is mostly a matter of the regulatory system. So there is some regulatory efficiency to be gained. Solar companies themselves also have some possible efficiency gains. Fortunately, the net price for solar continues to go down, with another 50-60% decrease in total price possible even without further technology gains. Commercial and grid scale solar is even cheaper – with large non-residential installations down to $2.4 per watt. It is primarily for this reason that solar is now the most common new source of added grid capacity. Worldwide, wind and solar are responsible for 85% of new grid capacity, with solar making up 73%. Worldwide there is now about 3 TW of installed solar capacity. One TW was added in just the last two years, showing the exponential increase in solar installations. Solar now generates 9-10% of the world’s electricity. This is led mostly by China, which as 50% of the world’s installed solar. For a long time, while wind and solar were increasing rapidly, they were more than offset by the total increase in electricity demand. This is still much better than not installing renewable or low-carbon energy, but it meant that fossil fuel use was still increasing. For the first time, however, total electricity from fossil fuels decreased, by 0.2%, without being caused by an economic downturn (like COVID). This is a tiny decrease, but it is a potential milestone if we have truly turned a corner. Even better, this decrease is driven primarily by coal, which is the dirtiest form of energy. Natural gas plants are still increasing, because they are still necessary for peaker plants, and because of the increased demand of data centers. The rise of solar is helping push down demand for fossil fuel energy, but there are two other factors that will be critical to push them down further. The first is grid battery storage. Battery technology is also improving rapidly. The advent of cheaper sodium ion batteries (which also bypass the lithium bottleneck) is seeing battery grid storage rise considerably. More and more of those home solar installations include battery back up. There are also new innovations, such as plug and play home battery backup, where you can add storage capacity in a modular fashion without any installation costs – just plug them in. Regulations need to catch up to this technology, allowing them to be used for whole home backup, but for now they can be used for targeted backup, like for your refrigerator, or your work station. Grid storage has the capability of reducing reliance on natural gas plants. So does nuclear. We seem to be at the beginning of a revival of the nuclear power industry. This is necessary even if we wish to simply maintain the current percentage of nuclear on the grid, which will help keep fossil fuel use down. The bottom line is that the cost of solar has dropped precipitously, and so if you have not looked into it recently, you should take another look. The prices I gave above were for a fairly large home. The total price of the system scales with the size of the house, which is a marker for the financial resources of the owner. Let’s say you have a more modest house that only needs a 5 kW system. If you pay for it outright, the total cost would be $15,000. The federal tax incentive just ended on Jan. 1, 2026, which is unfortunate but is defensible due to the fact that the cost of solar has dropped so much. However, 30 states still have some incentive, which can save thousands of dollars. But that aside – $15,000 is very affordable. How much this would save depends on a lot of variables, but for an average home in the US it would be between $800 and $1,500 per year. That means the payback time is between 10 and 18 years. After that, you essentially have free electricity. The useful life expectancy of a new system is 25-30 years, roughly double the payback time. Most solar companies now bundle solar installation with batter backup systems. This allows for peak shaving, and backup during outages. There is potential money savings here as well (including every time you don’t loose a freezer full of food). Further, many states offer incentives for batteries as well, if you allow them to use your batteries for grid storage. A battery system can also keep your solar panels functioning during a power outage. The trend lines for solar and battery grid storage are pretty dramatic and there is every reason to predict that they will continue, as further incremental technology advances take place and economies of scale kick in. The post Solar Is Booming first appeared on NeuroLogica Blog.
I am back from an almost three week trip to LA, Sydney and Christchurch. Sorry I did not have time to keep up with my blog over that period – in which we recorded four live SGU shows, produced three days of conference content, put on two stage shows, and hosted several other events. It was a tremendous amount of fun, but also a great deal of work. I am now jet-lagged and fighting off the remains of a viral infection I picked up along the way. Such trips always reinvigorate my dedication to science communication and scientific skepticism. I appreciate every conference-goer who came up to tell me about their personal journey and the role the content I have helped produce had played in it. I thought I would share some further observations from the trip. First, while the skeptical movement, such as it is, has been through a lot, it is still alive and well. The crowds we are able to attract to these events remain robust, and in fact are larger than many past events. There is a lot of enthusiasm for science and critical thinking. There is also a deep hunger for developing the skills to navigate our increasingly complex world. How do we deal with what social media, growing misinformation, deep fakes, and now artificial intelligence has wrought? People also have a deep desire for community – the kind of community that comes from getting physically together for a shared purpose, not just online. The number of people we can reach in these physical conferences and meetings is much smaller than online, but I think it remains a critical complement to online content. It also reinforces what I think many of use have learned from the “social media” phenomenon. Online communities are not the same as in-person communities, just online. People interact differently in person and online. The dynamics of social media were simply not what many of us expected. I don’t think we should abandon social media (although I know people who make a reasonable argument that we should), but rather we need to have a more realistic view of its strengths and weaknesses, its vulnerabilities and psychological effects. The conference goers were pretty similar, demographically, to what they have been over the past 30 years, which means there seems to be a steady state of younger skeptics entering the movement. There are more women than in the past, but still very few people of color – a social nut we have yet to crack. The issues about which people are interested are dramatically different than in the past. At a similar conference in the 90s or even oughts, there would be many questions about Bigfoot, UFOs, astrology, snake oil, and similar pseudoscience. Today people are interested in science denial, misinformation, AI, the trans debate, and similar societal issues (although snake oil is still prominent, perhaps more so). This is also the first big international trip I have taken since COVID and Trump 2.0. People in Australia and New Zealand had similar reactions, it seems. They still consider the US an ally, but they are deeply saddened, frightened, and perplexed by US politics. The first Trump administration could be dismissed as a fluke. The second, they reasoned, is evidence of something deeply wrong with American politics, something that might endure past Trump. This means that the US is no longer a reliable partner, and they must hedge their bets. They need more independence and need to carefully calibrate their relationship with China. There was also a strong consensus that this change is permanent – we will never fully recover our place in the world post-Trump. Interacting with people outside the conference was also interesting. Many people were still friendly, but some were cold or even passively hostile when learning we were Americans. It was nothing we couldn’t overcome with a bit of humor, but it was still disconcerting. It was also interesting being away from American media for three weeks. New Zealanders are chill, what a local New Zealand political scientist described to me as “low voltage”. Everything seems to be working fine and their politics are fairly low stakes. Australians are a more rowdy bunch, but still pretty low drama. It was just refreshing being away from the constant culture wars and American media stoking outrage and controversy at every turn. It really brought home how toxic American politics has become. But now I’m back. I guess I have to start looking at American news again. Perhaps I’ll wait until my cold is over. The post Back From Down Under first appeared on NeuroLogica Blog.
I often get questions like the one below: “I live part time in Japan. Everyone sees hydrogen powered generators, trains, trucks, etc regularly. High density population means it’s easy to get enough synergy to justify the infrastructure. So sad we aren’t doing more to utilize this great tech. Hydrogen combustion engines emerge as cheap alternative to fuel cells.” https://asia.nikkei.com/business/energy/hydrogen-combustion-engines-emerge-as-cheap-alternative-to-fuel-cells This is often how news about advances in hydrogen tech are framed. The problem is – the limitations with hydrogen technology have nothing to do with the tech itself, so tech advances are mostly irrelevant. Also, hydrogen combustion is not a better solution for most use cases then hydrogen fuel cells. Fuel cells use an electrochemical process to combine hydrogen and oxygen, producing electricity and water. They are about 60% efficient, produce no pollution, and have no moving parts. Hydrogen combustion operates more like a regular engine, but with hydrogen as the fuel. They are about 40% efficient, produce nitrogen oxides as pollution, and have moving parts that operate at high pressure and temperature. They can be, however, more powerful for heavy applications and are cheaper to build. For cars hydrogen combustion is a terrible idea. Maybe there is a use case for large generators, trains, and heavy trucks. Even there, however, there are current limitations that the technology of hydrogen engines or fuel cells do not address. 1 – Storage is a problem. They never figured out the storage problem, so just reverted to compressed hydrogen gas. There are efficiency, range, and safety issues with this. Plus, hydrogen is very leaky and destructive to infrastructure like pipes. 2 – Only about 1% of the world’s hydrogen production is green. Most of the rest is gray – essentially stripped from hydrocarbons. This is actually worse then just burning the hydrocarbons for fuel. If we do manage to ramp up green hydrogen production, it should be used first in industry, like steel production. Massive green hydrogen for transportation is a long way off. 3 – Even if we solve 1 and 2, hydrogen cars are less efficient than battery EV, and always will be (60% vs 80% efficient). This is just physics. Further, battery tech has simply advanced more quickly than hydrogen, and it continues to advance. Hydrogen lost this technology race. We may be able to fix the first issue with new materials, but until we do this is a major limitation. This is the main reason that the “coming hydrogen economy” promised back in the early 2000s never happened. There are three promising ways we may solve the second issue. The first is scalable green hydrogen production. If we had solar arrays or wind farms generating electricity to electrolyze water into hydrogen and oxygen, that could produce green hydrogen. The problem here is – we would be better off using that green energy for electricity. Round trip energy efficiency (electricity to hydrogen back to electricity) is only 30-40%. Better to use the electricity directly. Until we have decarbonized the energy infrastructure, don’t use green energy to make hydrogen for light transportation. Where there may be reasonable use is for hydrogen for heat-intensive industries, like steel, and for heavy vehicles like trains and ships. The second possible solution is if there turns out to be vast reservoirs of hydrogen under the ground we can tap into (so-called gold or white hydrogen). This remains to be seen, however. A third potential source is as a byproduct of nuclear reactors. Any reactor can make some hydrogen by radiolysis – splitting water by radiation. High temperature reactors can also make hydrogen through thermal methods. And any reactor can use their electricity for electrolysis, but this has the same issue as using renewable power. The third issue I think is just inherent to these processes. Battery EVs are likely to be always more efficient than hydrogen fuel cells. There may have been a window 20-30 years ago where hydrogen fuel cells could have leap-frogged BEV’s, but that window is now closed. Battery technology won, and also continues to steadily improve. Even if we make progress in hydrogen fuel cells or hydrogen combustion, we still have a hydrogen storage and transportation bottleneck. There have been advances here as well, but they come at a cost. Liquid Organic Hydrogen Carriers (LOHCs) can bind hydrogen to a fluid for easy storage and transportation, then heat the fluid to release the hydrogen. However, this has massive infrastructure and energy requirements, and would further reduce the energy efficiency of hydrogen. We have also engineered better storage tanks – Type IV tanks, which feature a seamless polymer liner fully wrapped in high-strength carbon fiber. This doubles the pressure under which hydrogen can be stored, doubling the range of hydrogen fuel cells. But it takes 12-15% of the energy stored in the hydrogen to compress it to these higher pressures. A hydrogen economy for transportation would have massive infrastructure needs, from production to pipelines, storage, and distribution, likely to take decades. This is all just to get us to a system that is less efficient than BEVs with similar range. Meanwhile there is already existing battery technology with twice the range of common BEVs today (silicone anode Li ion), or similar range at half the cost (Na ion). Solid state and lithium air batteries could potentially five times or more today’s energy density (1,500 vs 300 kWh). Meanwhile we are already near the theoretical limit of compressing hydrogen (700 bar). At 1000 bar hydrogen atoms repel each other and you get exponential energy requirements for further compression. If we are going to invest in infrastructure, those investments should go to fleshing out a fast-charging network for EVs and securing raw materials for making batteries. The post Hydrogen Tech first appeared on NeuroLogica Blog.
I came across a few news items that I could possibly write about today and couldn’t decide which to cover, so I will write about all of them, since they all relate to renewable energy. The first is a new study comparing direct air capture (DAC) to installing new wind and solar. This is a direct comparison between these two options, to see which provides the most bang for the buck. DAC involves taking CO2 directly out of the atmosphere in order to mitigate carbon release through burning fossil fuels. If this technology were sufficiently efficient it could be hugely useful in reducing future climate change. This is the only approach that can potentially have a negative carbon footprint, actually reducing the amount of CO2 in the atmosphere. Other technologies simply reduce the amount released. This negative carbon factor is highly attractive since it could theoretically zero out our carbon release and even take us back in time to an atmosphere with less CO2. Right now, it should be noted, we are not only continuing to release massive amounts of CO2 into the atmosphere, the amount continues to increase. In 2025 the world emitted 38.1 billion tonnes, of carbon, a 1.1% increase over 2024. But there are problems with DAC – it is currently not very efficient and is not scalable enough to have enough of an impact. Also, the efficiency of DAC depends heavily on how you power it – if you connect it to the grid and there is some fossil fuel energy on that grid, you may actually increase CO2 rather than decreasing it. Ideally DAC would be powered entirely by low carbon energy sources. This is why critics of DAC argue that it simply makes no sense to deploy this technology before we have decarbonized the energy sector, which we should do first. In the current study they ask a critical question – if we directly compare DAC to deploying wind and solar, which provides the greater reduction in energy pollution per dollar spent. They also considered both the environmental and health impacts. They further considered three scenarios – current DAC technology, significant advances in DAC technology, and a massive breakthrough in technology. They also did their analysis for the entire US and for different regions. What they found was that deploying renewable energy was more cost effective for every region of the country under the current technology and significant advances scenarios. In the massive breakthrough scenario the results were mixed by regions, with a slight net advantage country-wide to DAC. In my opinion this just adds to the conclusion that we should first decarbonize the grid with a combination of low carbon energy sources, including maximizing wind and solar while maintaining or even expanding our nuclear infrastructure, and only then invest in significant DAC. We can continue to research DAC in the meantime, and then deploy only when it gets significantly more efficient, in order to offset industries that are difficult to decarbonize. There are a couple of solar power updates worth discussing as well. The first is that we are getting very close to commercializing tandem silicon and perovskite solar cells. Silicon is the current standard, with most commercial panels at 22-23% efficiency, with high-end panels at about 26%. This is pushing up against the theoretical limit for silicon (32%), and many experts think we will not get much closer to this theoretical limit because of some unavoidable sources of energy loss. This is where perovskite comes in – this is widely considered to be the next material to replace silicon in high efficiency solar cells. But even better, silicon and perovskite absorb light at different frequencies, so when you combine them in tandem you get even higher efficiencies. The current record is produce by LONGi (a Chinese solar panel company), with a commercial tandem panel with verified 34.6% efficiency. They plan to make these panels available in 2027-2028. Also, the theoretical upper limit of efficiency of this tandem design is 43%. However, perovskite still has a longevity problem. For these tandem panels the silicon component lasts 20-25 years with minimal efficiency loss. The perovskite, however, only lasts 10-12 years. This is insufficient for residential use, but still useful for grid-scale projects. With large projects it is cost effective to pay for the higher end panels, and replacing them with even better panels in 10 years is not a bad investment anyway. But home owners don’t want to do this. However, there is a great deal of research into extending the lifespan of perovskite panels (for example). Another Chinese company, GLC, has announced a tandem solar cell with a 25 year warranty, and with an efficiency of 26%. We are quickly heading for panels with both efficiencies in the mid 30s and a lifespan of 25 years. The availability of relatively cheap and highly efficient solar panels has also given rise to a new industry – plug-in solar (also called balcony solar). These are stand-alone panels you simply plug into a regular outlet, which can both accept and deliver energy. That’s really it. You have to mount it somewhere, but most people do not put it on their roof but rather on a stand or attached to their balcony or similar structure. This is useful for renters, apartments, mobile homes, remote locations like cabins, or even to supplement existing rooftop installations. In general you will recoup the cost of the panel in reduced energy bills in seven years, while the panel itself should last for 30 years. These are already very popular in Germany where they have been used for a decade without any safety issues. Utilities companies in the US have been trying to slow their adoption, arguing that they present safety issues. For example, if they are sending current to the grid they could endanger utility workers. However, this is likely a diversionary tactic to slow the adoption of a competing technology. Units are already designed not to send energy to the grid when there is a power outage. The safety record in Germany is pretty solid evidence that they can be used safely. For most users plug-in solar would not power their entire home, but would shave money off their energy bill and reduce their carbon footprint. The great thing about plug-in solar is that there are no issues with grid stability since most users will be simply reducing their baseload demand, not producing excess energy that has to go to the grid. But because they can be widely distributed, these small reductions in grid energy demand can be significant. This could be a useful supplement to grid-scale and rooftop solar. And of course they can be especially useful when paired with home battery backup, or even just an EV. With recent events in the Mideast, including national average gas prices at $4.45 per gallon and electricity costs up 7.4% over last year, it seems like a good time to push for energy technologies that are not reliant on a vulnerable infrastructure partly in unstable parts of the world. These events also highlight that we can never achieve true energy independence simply by producing more oil, as oil prices are set as a global commodity. Solar, however, can be true energy independence, harvested right where it is used. Of course, this raises an entirely different discussion about maintaining domestic renewable energy technology and raw material supply chains. This is why invested in the technology of tomorrow rather than doubling down on fossil fuels is so critical. The post Some Renewable Energy Updates first appeared on NeuroLogica Blog.
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Last week the NSF issued a new memorandum describing the changes that they plan to make in agency programs and operations to implement the Golden Age of Science ideas advocated by the White House Office of Science and Technology Policy. It has been reported (Science, Nature) that many scientists are concerned about what is in the memo. The first words of the Science article: “For many U.S. scientists funded by the National Science Foundation (NSF), the agency they know and loved died on 10 September.” I will try to lay out why some people feel that way. The memo outlines changes to operations that will fundamentally alter the character of the agency. Generally most of the ideas are not a priori bad if the agency were in an environment with greater resources, when experimentation with alternative funding schemes and evaluations was not a less-than-zero-sum proposition. Instead, these ideas are being put forward at a time when the NSF is underspending (for no obvious reason by the non-technical people in leadership roles) its appropriation for FY26 by around 18%. This self-imposed budget austerity takes a bad situation (great uncertainty for everyone, drastically reduced staffing, delayed/eliminated/consolidated programs) and makes it considerably worse. Now this memo outlines plans to take resources away from historically core programs and redirect them to new, untested initiatives, and to do so in ways that don’t always seem internally consistent. The memo talks about trying to fund certain investigators for longer periods (e.g. five-year awards) with minimal goal direction (so that PIs are free to explore where ever the spirit moves them – across all of NSF’s portfolio, or only in chosen administration priority areas?), but there is no adequate discussion of how those people will be chosen. At the same time, there is talk of “golden tickets”, where individual reviewers in an already stripped-down review process can earmark some proposals for elevation, again with little explanation of how this will work. Without careful safeguards, this combination seems problematic, and the assertion that this will lead to higher risk/higher reward research unsupported. The memo also talks about short-duration, small budget awards for really risky proof-of-concept ideas. This isn’t crazy and the EAGER program has been good, but the idea that the key to enabling success in high-risk research is to reduce the budget and the timeline doesn’t make much sense to me. There is a through-line that the agency is trying to treat workforce development as separate and distinct from funding research projects. As the Science article says, “Traditionally, most graduate students and postdocs are funded through a research grant to their adviser or lab chief. But that will no longer be the case. Instead, the memo says, ‘Talent development funding opportunities may be coordinated with [research]-focused activities, as appropriate, but will be distinct and goal-oriented efforts.’” The memo mentions nurturing talent through the NSF Graduate Research Fellowship program and proudly talks about how this was just renewed. What it doesn’t tell you is that it was renewed at a considerably lower level than in previous years, which seems completely at odds with the claim of bolstering the program. Similarly, the memo talks about expanding access to shared infrastructure like cleanrooms, etc., but stated targeted funding levels of programs like the NQNI are no higher now than they were 12 years ago, not even accounting for inflation. (I assume they will actually make NQNI awards.) If NSF leadership keeps slashing their own budget, in defiance of congressional appropriations, it won’t matter what their priorities are. Lastly, let’s talk about “metascience”, the comparative study of different research funding models and practices, with the goal of a “self-improving NSF”. Again, the essential idea of doing careful studies of alternate funding mechanisms and research team structures and practices to improve research outcomes (not a trivial matter to define) is not bad. Doing this well is hard, because of several obvious reasons: How do you define successful research – by scholarly impact, by patents/economic impact, by production of educated scientists, some weighted average of these? On what timescale do you do this evaluation? The Einstein-Podolsky-Rosen paper was hardly cited for decades, and it is now arguably one of the most influential papers of the last hundred years, with enormous impact on quantum science and technology. How do you have sufficiently large samples and sufficiently long constant overall conditions to get reasonable statistics? There are strong practitioners of metascience out there, but when the memo says “These efforts ultimately serve a concrete ambition for NSF to double the scientific productivity and impact generated by each federal research dollar by 2036”, how can one take that seriously? No definitions of productivity or impact, and an implication that there will be optimization and major programmatic changes within less than two cycles of the much-vaunted five-year grants? The word “ambition” is doing all the work in that sentence. Oh, and while all this is going on, the agency (among others) has now eliminated language from its integrity policy that used to say that political interference in grants and operations is bad. I’m sure that’s nothing to worry about. There is tremendous uncertainty in funding from multiple agencies these days, and this has resulted in many universities cutting back on doctoral admissions in the sciences and engineering. This guarantees that there will be fewer PhD recipients in a few years across these disciplines. The large majority of PhDs in these areas do not go into academia and instead have formed the base of technical knowhow across diverse sectors of the US and global economy for decades. Cutting the supply like this will definitely have long-term consequences beyond just the halls of academia, affecting US competitiveness in ways that will take years to unravel. Adding to this uncertainty is not helpful to anyone. These are among the reasons why many find it hard to read that memo in the context of everything going on and feel optimistic that the proposed changes in NSF operations and direction will lead to a golden era for research.
[Note that this article is a transcript of the video embedded above.] I love the periodic table of the elements. I love it because it reveals the deeper order of what seems like an otherwise wildly disparate collection of atoms with different physical forms, chemical properties, and nuclear stabilities. I love it because, even before we actually found the elements that fit into each box, we knew that something did and could even predict some things about those elements before they were ever discovered. And finally, I love it because it’s a bit messy. Not everything lines up perfectly, and in some ways, it’s still a work in progress. In many ways, human-created standards follow that same form, and I want to try and convince you that they deserve the same affection. Let me present the periodic table of standard North American electrical connections. Isn’t it beautiful? I’m fascinated by stuff like this: a diversity of needs and purposes put into a relatively nice, neat order. But why do we need so many? And where do any of these actually get used? Well, I’ve spent the past month reading just about everything I could find on electrical plugs and receptacles to figure those questions out, and I even have a few of them here so I can show you what I learned. I’m Grady, and this is Practical Engineering. Electricity is something we really don’t want to be proprietary. It’s one thing if your charger doesn’t work on your buddy’s cell phone. It’s another thing entirely when you have to rewire your house because you bought a different brand of toaster. The National Electrical Manufacturers Association, or NEMA, was founded in 1926 as a coalition of companies making electrical equipment. Their members realized that life would be better with some standards, so that any company making an electrical device could be reasonably confident that the people who might want to buy that device would be able to use it, and more importantly, use it safely. This didn’t happen overnight. It took a diverse group of manufacturers, engineers, and testing labs to form a consensus around the system we use today. And it’s far from a perfect system. My friends Mehdi and Alec have covered receptacle-related topics on their channels, including the merits and disadvantages of the NEMA designs. But it works pretty well. Well enough that the NEMA connector standards have been adopted not just in the US, but all of North America, Central America, parts of South America, Japan, Taiwan, the Philippines, and beyond. Here’s that table again. You probably noticed that every type of plug and receptacle has its own special number. They seem a bit arcane at first glance, but it’s actually a handy naming scheme that’s pretty straightforward to understand. The first number is the configuration that defines the combination of voltage rating, wire count, and grounding style. These numbers are a bit arbitrary, but they kind of represent a certain class of receptacles and plugs. For example, NEMA 1 receptacles are rated for 125 volts and have just 2 poles (a hot and neutral) with no ground. The NEMA 1-15 was the classic North American outlet until the 1960s, and you still see these in older buildings. Lots of devices made today can still use them, especially low-voltage equipment like chargers, and, critically, those without external metal parts. If an energized wire inside the device comes loose and contacts the case, there’s still an insulating barrier protecting someone from being shocked. The reason NEMA 1 receptacles are mostly a thing of the past is what could happen when equipment didn’t have that protection. If a device with a metal enclosure or exposed metal parts had an energized wire come loose, that metal would be energized too. But, critically, it might not create a short circuit. With nowhere for current to flow, the device could just sit there, indefinitely dangerous, until someone happened to touch it, allowing current to flow through them to a lower potential. The ground wire we see in nearly all plugs and receptacles today fixes that specific hazard. Bonding exposed conductive elements and connecting them to ground makes sure that if they somehow become energized, current will flow, a short circuit will form, and protective devices like breakers will activate. Today we use the NEMA 5 standard for the vast majority of receptacles and plugs. Even if you’ve never heard of NEMA or seen the other plugs on the periodic table, you’re almost certainly familiar with this design. They have a 125 volt rating to handle the standard 120 volt service for most electrical devices with a little buffer. They have an energized pole, called the hot; a neutral pole to provide a return path, and a separate ground return that is bonded to the neutral line in the main electrical panel. The ground pin on most outlets is round instead of flat, and that’s the reason why nearly all electrical outlets kind of look like they’re screaming. Or at least they do to me. One thing about NEMA 5, and actually most of the NEMA configurations, is that the outlets have polarity. On the NEMA 5-15, the neutral slot is a bit wider than the hot, making it so the plug can only go in one way. In function, polarity often doesn’t matter for AC circuits. Current travels in both directions, so the equipment inside the device can’t really tell the difference. And some devices, like switch-mode power supplies, don’t care which direction they’re plugged in. Both blades are the same size. For safety, though, a lot of devices do. You really don’t want heating elements, motor coils, and circuit boards energized and waiting for a ground. It’s less hazardous to put the switch on the hot wire so that nothing beyond the cord is energized until it’s turned on. Enforcing polarity at the plug prevents “switched neutrals” along with other issues like electrical noise. The NEMA 5-15 plug and outlet were designed to be backward compatible with the older 1-15 standard. 1-15 plugs work just fine in the modern 5-15 outlets, and there are quite a few interesting compatibility cases like that in the NEMA standards. For example, the “15” in 5-15 refers to the current rating. Nearly every household device and appliance that runs on 120 volts is designed so that it never draws more than 15 amps, and actually, if the device is meant to run for more than 3 hours continuously, like a space heater, it can only draw 80% of that (which is 12 amps if you’re keeping score at home). That limit is obviously fine for most household appliances. But, especially in commercial spaces, it’s not quite enough power for certain devices like kitchen mixers, treadmills, copy machines, and power tools. Of course, we could just change the codes to require 20-amp circuits everywhere, but that has huge implications: larger circuit breakers, heavier-gauge wiring, and more expensive receptacles. And in many cases, it’s just not necessary. So instead, NEMA created a different receptacle and plug for 120-volt, 20-amp circuits, the 5-20. I have a bunch of these in the studio. You can see they have that T shape on the neutral slot. And 20-amp devices have the neutral blade rotated 90 degrees on the plug. But here’s the backward compatibility: regular 15-amp plugs fit into the 5-20 receptacle as well. NEMA 5 has 30 and 50 amp receptacles too, although they aren’t used very often these days because of a quirk about the historic availability of voltage. Today, split phase electrical service is basically standard for residential power. You get two 120-volt hot lines which can be used individually for smaller circuits or combined to get 240-volts for circuits that need more oomph. In the early 20th century, 240-volt service wasn’t always available, so you have these very-high-current 120-volt receptacles that could power heavy commercial cleaning equipment like floor burnishers and blowers, kitchen equipment like warming cabinets and steam tables, and large shop tools like table saws and compressors. Also, not all portable generators run at 240-volts, so older models used the larger NEMA 5 receptacles as well. These are still available and installed in places where, for whatever reason, a higher-voltage circuit is hard to come by. But in most cases, the more power-hungry devices are going to run on 240-volts. That brings us to NEMA 2. Like NEMA 1, these are ungrounded receptacles, but instead of a hot and neutral, they have two hots. Each is 180 degrees out of phase with its neighbor, so you get 240-volts across them, handled with a little cushion by the 250-volt rating. There were 20 and 30 amp receptacles, but, also like NEMA 1, these are mostly obsolete now that a ground is required by code. They’ve been replaced with NEMA 6, which has 15, 20, 30, and 50-amp receptacles and plugs. Of course, with double the voltage, you also get double the power compared to the NEMA 5 equivalents at the same current rating. The 6-15 is common for window or wall-mounted air conditioners. The 6-20 is used for heavier-duty air conditioners plus commercial kitchen equipment and shop tools. The 6-30 is used with large heaters, kilns, and heavy power tools. The 6-50 is kind of the standard welder outlet, plus it’s pretty common these days for level 2 EV chargers, capable of delivering nearly 10 kilowatts of continuous power through the receptacle. Like NEMA 5, the NEMA 6 has some backward compatibility, allowing 6-15 plugs to fit into 6-20 receptacles. This is kind of clever, but it doesn’t work all the way up the different current ratings. Of course a 50-amp outlet could easily handle a 15-amp device. And it would certainly be possible to design a series of outlets where each successive jump in current rating allowed those smaller devices to plug in. But there are two main reasons why they don’t: One is practicality. The blades on plugs aren’t all the same thickness. Designing a single receptacle slot that can safely grip both a thin, 15-amp blade and a massive 50-amp one would make manufacturing more difficult and increase the chances of developing loose connections inside the receptacle over time. Two is safety: circuit breakers are sized to protect everything downstream, including the plug and the appliance cord. If a thin cord on a low-current device develops an internal short, the resistance of that thin wire itself will cap the fault current so that a larger breaker might take much longer to trip or not trip at all. That could allow the wire to reach high enough temperatures to start a fire. Of course you don’t want a high-current device plugged into a lower-current-rated circuit, but if you trace out the things that can go wrong, it turns out that you also don’t want lower-current devices plugged into a high-capacity circuit. So, the plugs and outlets are designed to prevent both cases, except for the 15 and 20 amp situation, where the current is close enough that a breaker should still work as intended. 240 volts are useful to supply more power at the same current rating, but of course it comes at a cost. Higher voltage means more potential, literally, for arcs to occur. Equipment designed to handle the higher voltage needs better insulation and more careful design. Take a clothes dryer for example. You want the extra voltage for the power-hungry heating elements, but all the other stuff inside (like timers, controllers, and clocks) can easily run on 120 and those lower-voltage components are more affordable. That’s where NEMA 10 came in. You get three poles: two hots and a neutral. In that way, you get dual voltage: 240 between the hots and 120 between each hot and neutral. Of course, NEMA 10 receptacles also lack a ground connection, so they’re mostly obsolete. Plenty of houses still have them installed for clothes dryers and kitchen ranges, but since the 1990s, they’ve been supplanted with the NEMA 14 configuration. This is the most widely-used 240-volt standard in North America today. It’s versatile, providing both voltages. And there are a full range of current capacities, allowing you to design a circuit that’s well-suited for a device, from 15 all the way up to 60 amps. The 14-15 is pretty rare. I couldn’t even find someone making the receptacle. The 14-20 is also not that common. Some food service equipment uses this like certain coffee makers. The warmers rely on 240 volts while the fans and timers run on 120. Same with some jobsite heaters and specialized laboratory equipment. The 14-30 is the standard residential electric clothes dryer plug and is often used for EV chargers. Some server and mainframe equipment uses it as well. The 14-50 is the standard residential cooking range and oven plug. It’s also widely used for EV chargers and pretty common at RV campgrounds as well. The 14-60 is more of a commercial or industrial receptacle, used for large kitchen appliances and distribution of power at events like concerts. Single phase electrical service covers nearly all residential and lots of commercial buildings. But, the grid runs on three phases and it’s pretty common for larger commercial buildings and essentially all industrial facilities to have three-phase service. It’s particularly useful for devices that use large motors. And of course, if you have the service, you’re going to need receptacles and plugs for those devices, or at least the ones that aren’t hard-wired. NEMA 11 was the standard for up to 250V with receptacles and plugs ranging from 15 to 50 amps. Those have been replaced by the new NEMA 15, again because of grounding requirements. And this is going to almost always be relatively specialized industrial devices: woodshop and machining tools, laboratory testing equipment, grinders, pumps, dust collectors, heavy welders, plasma cutters, and so on. It’s not stuff most people see in everyday life, and in many cases, each receptacle is going to be custom-installed for a specific piece of equipment. And since hard-wiring equipment directly to the service panel is typically the default, that makes receptacles like these even more rare. You really only see them in places that need a high degree of modularity, allowing for rapid reconfiguration of workspaces like jobsites, certain manufacturing facilities, and short life-cycle equipment that needs to be easily swapped out. There are two main three-phase service classes used in most commercial and industrial buildings in the US. The most common is 208 volts phase to phase, which uses the NEMA 15 configuration. There’s also 480 volts phase to phase, but like I mentioned before, you can get a lower voltage between phase and neutral (in this case, 277 volts). So NEMA 7 has plugs and receptacles specifically for using just one phase from buildings wired with 480-volt, three-phase service. A lot of commercial and industrial lights use these receptacles, like warehouses, factories, and arenas, making them easy to swap out without hard-wiring. Commercial ventilation and air conditioning systems use them too. And just like the dual-voltage 240-volt plugs, there are also dual-voltage three-phase plugs, delivering equipment with all three hot phases plus a neutral so different components can run at different voltages. NEMA 18 has receptacles for 208-volt service, although they don’t have a ground, so they’re mostly obsolete. There are no straight-blade plugs that have replaced NEMA 18. Aligning and inserting a 5-blade plug would be tricky and take a lot of force. And I’ve kind of buried the lede here only talking about the straight-blade NEMA standards. The reality is that a large number of the NEMA receptacles and plugs have an equivalent locking version. These use curved blades that twist inside the receptacle so they can’t be easily pulled out. Actually the locking versions are more common than the straight-blade equivalents in many cases, especially when it comes to portable generators, jobsite equipment, and events where things are always moving around. If your vacuum cleaner unplugs itself because you’ve gone too far into the hallway, that’s usually not a big deal, but if a three-phase 600 volt plasma cutter does the same thing, you can get serious damage from arcing. That’s why the locking standards extend beyond the voltage ratings of the straight-blade ones up to three-phase 600-volt circuits. They even have receptacles for 400-hertz power used in aerospace, submarine, and military systems. Of course, sometimes the standards make themselves. When it comes to RVs and travel trailers, (from what I can gather) the industry had already developed a 120-volt, 30-amp receptacle before NEMA formalized its catalogue of standards. Instead of forcing an entire industry to retool, NEMA just adopted what everyone was already using, calling it the TT-30. TT for travel trailer and 30 for the current capacity. In function, it’s not any different than the NEMA 5-30 receptacle and plug, but you’ll almost never see one of those, because the TT-30 is far more common. It’s a face only an outlet enthusiast could love. I haven’t really talked about the smaller versions of the locking connectors used where space is an issue. And there are even more specialized standards like ship-to-shore power, aircraft, and military uses. Of course, when you look beyond NEMA, there are way more standards out there. But I feel like this is enough to get you excited about the weird, wide world of electrical receptacle standardization. There are all kinds of practical considerations that make it much more complicated than just a 2D chart with voltage on one side and current on the other. Just like the periodic table of the elements, the NEMA connection standards are a bit messy. And that’s what I love about them.
The course of history is affected by many things, including the political and social situations of large groups of people, […]
Rethinking the electric field Have you ever wondered what an electric field actually is? The electric field is the foundation of most technologies that we rely on every day. From power grids and electronic devices to radio communication and the … Continue reading →
We are less than one month away from the end of the federal fiscal year, and traditionally there are internal deadlines for agencies to allocate their final spending by around September 9. Right now, the NSF is on track to issue about 4000 fewer (!!) awards in FY26 than it did annually back in FY21-FY24, and 2000 fewer than it did in the incredibly tumultuous FY25 (with its government shutdowns and mass cutbacks in agency personnel). This is dire, if like me you are a supporter of the agency and its vital role in the US research ecosystem. Perhaps even more distressing, the NSF is on track to underspend its FY26 budget appropriation (congressionally approved, presidentially signed) by between $1.25-1.5B, or 15-18%. This is essentially unprecedented - in the past, the NSF has always spent ~ 99% of its appropriation in a given fiscal year. Some large portion of this is from the mid-FY clawbacks that were reported in Science and Nature, supposedly squirreled away to support an as-yet unannounced OSTP "grand challenges" program. While technically the funds don't go away at the end of September, this kind of underspending raises the possibility of a pocket rescission. OMB and the executive branch have been pushing for massive cuts to the agency; Congress has disagreed. It sure looks like all the "see, don't worry, Congress didn't allow big cuts to the NSF" palliative statements don't hold up very well to scrutiny, if the majority party is content to just give up Article I power to the executive branch. In this period of complete flood-the-zone craziness, the mainstream news media seemingly doesn't have the bandwidth or interest to report on this; they seem to have judged that it's too obscure, it doesn't play in Peoria, the public doesn't really care. This kind of disruption will have ripple effects that last for many years and affect US scientific and economic competitiveness, and it's happening without much notice. This week's news about an agreement between NIH and DOD to funnel NIH funds for infectious disease to DOD (or, in the official statement, to work together on projects of mutual interest), is at least getting some public attention. Agencies agreeing to pass around at minimum hundreds of millions of dollars outside congressional oversight or what the appropriations acts say is another example of an Article I crisis, when the majority party basically hands over what are supposed to be congressional powers to executive branch. (An additional sciencey blog post coming soon!)