What Is a Watt?

You are listening to Shift Key, Heat Maps Weekly Podcast about decarbonization and the shift away from fossil fuels. On this week's show, class is in session. Jesse is taking us through the basics of the energy system and the power grid, what is a jewel and what is up. It's all coming up after this. ShiftKey is brought to you by the Yale Center for Business and the Environment.

Do you want to accelerate your career in clean energy? Then it's time to explore online certificate programs from the Yale Center for Business and the Environment. Whether you're designing policy, unlocking financing, or developing important projects. Yale's online clean energy programs equip you with tangible skills and powerful networks, and you can continue working while learning.

In just five hours a week, propel your career and make a difference. Learn more about Yale's year-long financing and deploying clean energy program. Or their clean and equitable energy development program, which is just five months long, by going to CBEY dot yale dot edu. That's cb e dot yale dot edu.

This week on ShiftKey, we are doing something new. We are bringing you a new series. Everyone encounters the energy system in different ways. You turn on the lights, you turn off the lights, maybe you pay a power bill, maybe you drive a car somewhere. Some of you may even work in climate or electric vehicles or energy every day. But not everyone has the same background in the power system or the energy system.

And we know this podcast touches on a lot of technical material that you may not know. Some of you may not even have a technical background. I should say I don't have a technical background. I was a music major and so there may be information that we touch on in this show every week that you don't have. And we want to give you that information. So this week we are going back to basics. We're going to do what we call Shift Key Summer School.

My co host Jesse Jenkins, as you hear at the top of every episode, is a professor of engineering at Princeton University. And he is going to take you and me to school with him for the next three weeks and then later this summer. We are going to have what I've kind of dubbed lecture conversations between Jesse and me every week.

with Jesse discussing the real material he teaches in his introductory classes, and I will serve as the student. As you'll hear, I may know a surprisingly little amount about some of these topics as the student. So let's begin. On the syllabus this week are the very basics.

What is energy? What is power? And how should you think about the major electricity units that you hear us discuss on this show every week? You know, kilott hours, megawatt hours, gigawatt hours, all of that. It's all coming up on ShiftKey. Jessie, let's start.

Yeah, let's start at the big question. I mean, energy is a weird thing, right? Because it comes in so many different forms that it takes on all kinds of different units, as we'll talk about here later, and it can kind of be dizzying as we convert back and forth between different forms. And also we only really experience it like in a physical sense in a couple of its forms, unless you're shocking yourself you're not really feeling electricity on a regular basis, right? And so I like to think of

energy to start with in kind of its basic define its basic terms, right? It's basic scientific information units, SI terms. And then to get a physical intuition for those units. So let's start with the Joule. All right. The Joule is the SI unit for both work and energy. And the basic definition of energy is the ability to do work. not work in a job, but like work in the physics sense, meaning we are moving or displacing an object around.

So a joule is defined as one Newton meter, among other things. It has an electrical equivalent to a Newton is unit of force, and so force is accelerating a mass, right, from basic physics, over some distance in this case, so one meter of distance. So we can break that down further, right? And we can describe the Newton as one kilogram accelerated at one meter per second squared. And and then the work part is over a distance of one meter.

So that kind of gives us a sense something you feel like. A kilogram, right? That's two point two pounds. I don't know. I'm trying to think of something in my life that weighs a kilogram. I don't know, a a a couple pounds of food, I guess. A liter of water weighs a kilogram by definition as well. So if you've got like a liter bottle of soda. There's your kilogram. And then I wanna move it over a meter.

So I have a distance I'm displacing it. And then the question is how fast do I want to do that? How quickly do I want to accelerate that movement? And that's the acceleration part. And so from there you kind of get a physical sense of this. If I uh something requires more energy. If I'm moving more mass around. Or if I'm moving that mass over a longer distance. Right? One meter versus a hundred meters versus a kilometer, right?

Or if I wanna accelerate that mass faster over that distance. Right. So zero to sixty in three seconds versus zero to sixty in ten seconds in your car. That's gonna take more energy to accelerate that that rapidly. I'm looking up. What way is Oh here we go. A Mac a thirteen inch MacBook Air. Weighs about a little more than a kilogram. So So your laptop. Yeah. If you want to throw your laptop over a meter, accelerating at a pace of one meter per second square. That's about a jewel.

That's that's about it. In one second. It's not a huge unit of energy. We obviously you're moving your body around, right? It weighs a little bit more than a kilogram, at least mine does. And you're moving around, accelerating all over the place, walking around, like that is using up energy on a regular basis. So joules are pretty small. And that's important'cause a joule a watt, which is actually a unit of power, not a unit of energy, is described as a joule per second.

So if energy is a quantity, it's something that we're consuming or producing or transporting or converting. then power is the rate at which we're doing that. So it if I have a if I'm consuming a joule of energy in a second, that rate of consumption is one watt. One analogy for that is like a bathtub, right? Like the amount of water in the tub, the volume of water, that's the energy. And the size of the faucet or the rate at which the faucet is adding water to your tub, that's power.

I'm raising my head. Didn't it make any sense? Yeah, okay. Robinson has a question. Yes, Robinson.

Well Okay, so I have a few questions. The first is I just wanna I think it is kind of important to establish like energy here, the jewel. What that changes about a substance and I realize this is like high school physics, physics one oh one, is the acceleration, not the velocity. Like we sometimes think of energy as a property of velocity, but as actually the ability to change velocity that Is what energy does, right?

Yeah, that's right. I think about the kind of basic Newtonian mechanics, right? If you're if you're in a you have an object in a vacuum with no friction, right, and no forces working against it, it will continue at the same velocity and the same trajectory forever. Right. And so the the what it requires energy is to change that direction or velocity, which requires acceleration or the application of force to some mass.

You just kind of said this, but like what is the difference between energy and power? Yeah, so energy is the is the actual thing that it's the quantity of the thing that's doing work, right? So it's the amount of fuel we burned or the number of calories we had to eat to run our bodies over the course of a day, or the amount of electricity we had to generate to run our our lights or our computer.

Power is the rate at which that energy is consumed or supplied or transported or transformed. And so it is not itself a unit of quantity. You don't use power. You use energy. Power is the rate at which you're using energy. So again, it's it's how quickly the bathtub is filling up or draining, not the quantity of water in the bathtub. So a a watt is the basic unit for the SI unit for power. Which is gonna be equal to energy divided by time, energy over some period of time. So

Power, energy and time are fundamentally related in that way. Energy is equal to power times time. So when we talk about electricity units of energy, we usually use the term watt hours instead of joules. That's a watt of power sustained over an hour. That's the quantity of energy that would be delivered over an hour if we were sustaining it at a rate of one watt.

So energy equals power times time, power equals energy divided by time, and then I guess time is energy divided by power if you want to think about it that way. So a watt is not specific to electricity. A watt we could actually talk about for any kind of energy. It's just the fact that we could even describe your car motor.

Yeah, and in fact in Europe they do that. They don't use w horsepower. That's another unit of power. It's kind of a weird one when you think about it, right? Like what is a horsepower? In the US we and in the UK we it's one horse's power. So yeah, exactly. There's no confusion about this. How big a horse? I have questions about this horse.

And in Europe you'll often actually see the motors, the engine power rated in kilowatts, which is your maximum power output from that that motor. Obviously when we switch to electric motors, that makes a lot more sense too, because now we're even talking about electrical power. And when we talk about like power plants having a number of watts or kilowatts or megawatts or gigawatts.

That's usually the maximum power output that plant can deliver. Right. So it's a rated power or maximum power. And it doesn't necessarily produce at that maximum power all the time. Right, think about a wind farm that's varying in its output with the wind or solar with the sun or even a nuclear plant that has to shut down for maintenance.

And so if you wanna understand how much energy a power plant produces, you have to know the power at which it's producing integrated over time, or what we call the capacity factor, which is the average power of that plant over a given amount of time.

I wanna go there in a second, but first I wanna make sure I understand something correctly, which is as an energy reporter Uh y or as a person who reads energy documents and reads energy stories, reads heat map, there's a discussion both of kilowatts, but really of kilowatt hours. And am I right to understand that one watt, if one watt times one second equals one joule, right? That's That's correct, right? That's like That's correct. A kilowatt hour is a

Even though it sounds like a chunky unit and sometimes I feel like it's a bit of a weird unit to throw around, it is the same it's measuring the same kind of thing that jewels are measuring. Yeah. In other words, when I throw my laptop one meter. And from that distance at one meter per second, right? That's actually The thing we're measuring by saying that I've just expended one joule of energy is the same ultimate substance that we're measuring when we say a solar farm put out. Sixty kilowatt.

Yeah, that's right. And that's like kinda worth pausing on because again, this is why energy is so slippery a concept, because it can come in so many different forms and we often use different units when we're talking about a different form. So when it's electricity, we often we talked about kilowatt hours or megawatt hours. We should like pause and say a kilowatt is a thousand watts, right? So a kilowatt hour is a thousand watt hours.

Um so we got all these prefixes too. But you know, you could so we've talked about defining energy in physical terms, right? Displacing a kilowatt over a meter at some at a meter per second squared of acceleration. But you can also think about it in heat terms. So, you know, heating up a body of water or heating up a room, right, that's gonna require energy to do that, right? Energy coming out of your your furnace or your fireplace or whatever else.

And we often have different units for that too. So calories are the standard unit in SI terms. Whereas we also often talk about British thermal units or BTUs in energy world. This is an imperial unit that we rarely use outside of the US. Those units are defined in terms of the amount of heat required to to usually to heat up some unit of water. So for example, a calorie is defined as the amount of heat required to raise the temperature of a liter of water by one degree Celsius.

And that's the kilocalorie, that's the big calorie. The small calories or gram calories is one millimeter of water raised by one centimeter. So that's the other way we can think about it as like a heat flux, right? That's what a lot of our energy goes to combustion, right, to generate heat and then do something with that heat. So that's another way to get a physical intuition for energy, but then often we use different terms.

Energy of course can also be contained in the chemical bonds of certain things. That's what we're combusting. We're breaking up the chemical bonds of wood or coal or natural gas. And so then we also talk about the heat content of or energy content of those fuels. And you can use jewels for that, you can use BTUs, you can use calories, you can use megawatt hours.

Or kilowatt hours. Or in many cases they use physical units to describe different types of fuels as well. So you might hear things like barrels of oil or millions of tons of coal. Those all have to be standardized units of energy as well, which just adds to the confusion. So one calorie. One kilocalorie, I believe. is four thousand one hundred eighty six joules. Yeah, of course. You can do that mental math in your head, right?

I do it all the time. So I think what's interesting here is that You know, the hu if you think about a standard this isn't quite standard anymore, but if you think about people eating two thousand calories a day, that means the human body's expending like eight point three million joules a day. Yeah. I think yeah, exactly. That's two point three kilowatt hours. So does that mean actually people use more How many what's a household use of kilowatt hour? Like one point something?

No, so a k a typical household in the US, and this would be less if you're in Europe or somewhere else, consumes a little bit over a kilowatt of average power. So that's the average rate at which they're consuming electricity. Now of course it goes up and down as you turn off d on and off devices, right? If I turn about twenty four kilowatt hours a day, right? So that exactly. So that's a little over twenty four kilowatt hours a day. So a a family of three.

Yeah. So according to the US Energy Information Administration, the average US household consumes about ten thousand five hundred kilowatt hours of electricity a year. So that's about twenty eight, twenty nine kilowatt hours a day, or about one point two kilowatts average over the course of the day. Well I'm now it's just thinking about, you know, the average diet for a person, right, is twenty five hundred kilocalories, which is yeah, about two point five kilowatt hours. So what?

Yeah, that's a good that's a good weight. Is using ten times as much energy as your body is at any uh through the day? And that's just the electricity. Yeah, that's just the electricity part of the energy too. If you're driving to work in a car that's not electric, you're not that's not counted in that energy consumption that you're and then you're consuming the energy in your gasoline. If you're heating your home with natural gas, right, that's not counted there too.

But yeah, to give a sense of scale, I like that. One one human is two point four kilowatt. hours or something like that. Four kilowatt hours is the amount of energy you'd need to run a window A C unit of a half a watt half a kilowatt for eight hours. So you want to cool yourself for eight hours a night while you're sleeping, that is four kilowatt hours. So usually we're thinking about most things we're doing that are like major energy users are in the kilowatt hour scale.

I like this'cause I think I mean I there's a certain d element to where this is getting a little matrixy where we talk about humans uh producing kilowatt hours of electricity, you know. But no, I I I like this'cause it makes sense, right? Um I have one more question, which is

in energy writing and energy reporting I think there's often It's very common, simply frankly, in writing to avoid echoes. To repeat to avoid repetition, to vary, referring to energy as power. Or referring to it as energy. Do you think that's okay? Do you think that's forgivable? Or are there moments where we're writing about power that we should be sure to call it power and moments where we're writing about energy? Because I think especially writing about the power grid.

Referring to electricity, energy and power, those things are basically treated as interchangeable even though from a physics perspective they are. As we've talked about here, the way we experience the grid is in terms of energy, right? It's in terms of the amount of energy we're using over some to do something useful. So I would recommend generally reporting it in those terms, in energy terms. And that's just because the rate at which we consume energy or the power.

varies dramatically as we're talking about over the course of a day. Do I have my EV charger on or off? Do I have my air conditioner on or off? Like these cause huge swings in the rate at which we're actually consuming that energy or the power rate.

And that's also true on the generator side too. You think about particularly we're talking about reporting the size of an offshore wind farm or a solar plant. You usually will hear that expressed in terms of its maximum rated power output. It's a three hundred megawatt wind farm.

That's the maximum it can produce or the maximum power rate at which it can produce. But it doesn't sustain at that rate all the time. And so the average power rate is much lower than that. And that's where this capacity factor concept comes in, which is basically the average Power rate divided by the maximum possible. So if we say a wind farm has a capacity factor of fifty percent.

then that three hundred megawatt wind farm, so that's three hundred megawatts of maximum power, is varying around between zero and three hundred, and on an average it's producing energy at a rate of one hundred and fifty megawatts. Even a nuclear plant isn't running constantly. That's as close as you get to an equivalence between a power rating and an energy output because it runs ninety percent of the time. But even there the nuclear plant turns off for

twelve weeks every eighteen months to refuel. And so it's not producing all the time either. So I would probably council describing things in energy terms for the most part, because that's what we actually experience as heat or as acceleration of mass or other things that we can feel in our daily lives.

Let's talk about scale for a second. So in writing about electricity and I'm writing about renewables specifically, you encounter these kind of like big units, right? You encounter watts, but you really encounter kilowatts, megawatts. Gigawatts and then at the scale of national systems, terawatts. And for ease of use. These energy units are almost always followed up by and this is the number of households it powers, right? This is the number of average households it's gonna.

But the thing is when you start digging under the surface, there's a huge amount of variance in those household terms. And I think it really obfuscates how people understand the energy system and the power grid. So like how much Are these units, if we want to switch to a unit first and a watt-first way of thinking about renewables and thinking about the electric thinking about electricity? How big is a kilowatt? How big is a megawatt?

What is the right comparisons to hold in our head for those that don't require just converting to like, oh, this is ten thousand households and this is a million households? Yeah, so again th if you're thinking in watts, you're talking about power. And so there again it's like are you trying to describe

An instantaneous power, a maximum power, and average power. Those are all different things. I think the key thing is if you're talking about power, you gotta start with what am I actually trying to describe?

And if I'm not actually trying to describe a unit of power, I'm actually trying to describe a unit of energy, which is like how much energy households use, then we probably shouldn't be using watts. We should be using watt hours or their equivalent. So that's my first point. Secondly, let's talk about scale. Yeah. Yeah. So to follow my own advice, let's start with the energy units first.

And and you'll get the the relationship here between energy and power to some degree in this explanation. So if I'm talking about the amount of energy that a computer, a laptop, or a light uses over an hour, for example. That's the scale of like tens of watt hours. So a ten or fifteen watt LED bulb, that's the maximum power it's consuming when it's on. So if you have a ten watt bulb on for an hour,

That's ten g watt hours. The draw of a typical laptop, if you look on the back, it's let me see what mine is. Yeah. It looks like my laptop is rated at sixty sixty ish watts of power draw. So if it's on an unmax I'm computing at its maximum power draw for an hour, then I'm used sixty watt hours. Personal electronics, light.

Those are on the scale of watt hours per hour. You know, so I'm you know, if I'm using it for days or weeks, then it might grow to a kilowatt hour. But if I'm thinking about kind of the near term use over a period of hours of a laptop, cell phone or an LED light, those are in the scale of watt hours. If we're talking about other larger consumers of electricity, or again, the scale of annual of daily use of a human, then we're at the scale of kilowatt hours or thousand watt hours.

So like you said, a human uses a little roughly two point five kilowatt hours of food a day. If you're running your air conditioning unit over the course of the day, that's gonna be in singles to tens of watt hour of kilowatt hours. Your solar panels on your roof. are usually on the scale of five to ten kilowatts of maximum capacity. And so they produce twenty five percent on average, maybe they're producing four kilowatt hours per hour on average and seven

kilowatt hours per hour and the sun is up, something like that. And your chargers as well. Your EV charger is also on the scale of several kilowatts also. Do you want to build critical skills that are transforming the clean energy sector? Then discover the Yale Clean and Equitable Energy Development Online Certificate Program from our sponsor, the Yale Center for Business and the Environment.

This fully online five-month program is designed for working professionals who want to build projects that serve both people and the planet. You'll dive into energy fundamentals, project finance, and key phases of development and operations. While learning how to center community engagement. In just five hours a week, you'll learn from leading experts. Develop practical skills, and gain actionable insights. By engaging in video lectures, live sessions, and a real-world group project.

Yale ensures you have the expertise to advance clean energy solutions that benefit communities and drive economic resilience. Are you ready to elevate your career and make a difference? Then visit cbey.yale.edu To learn more and enroll in the Clean and Equitable Energy Development Program, that's cbey.yale.edu or check out the show notes for more.

One reason load growth has come back, right, is because through the twenty teens, and at least this is my understanding, you should correct me if this is wrong, but through the twenty teens we were basically increasing the efficiency of the power grid. At the same time that we were adding new demand to the power grid. And we were increasing the efficiency because we were replacing the stock of incandescent light bulbs.

with LED light bulbs. Basically like that was the biggest story in electricity. And if just to go back to your units, like if you think about how much power an incandescent light bulb draws, it's like sixty watts.

And now, as you were saying, it's sixty to a hundred and now as you were saying a LED light bulb draws like ten. Like that's where the demand growth went during the twenty teens. And the fact that we've now basically finished converting You know, most light bulbs in the United States to

LEDs and but are still adding new capac like no wonder demand growth is back. Anyway, I just wanted to interject that because it was really I think it's evocative of how like we're talking about fifty watts per light bulb, which is a lot, but also how these small, relatively small differences in power units add up to massive utility scale decision making. Anyway, though. As you were saying. No, I think it's a E V. It drives a kilowatt. Yeah.

Yeah, EV is a little scale cool. Yeah, no, I that's helpful I think to remember. And it's interesting because of course

electricity was first used for lighting. That was its first application way back when. And now it's interesting that like l lighting has become so efficient that it's such a tiny sliver of the overall you know, electricity usage nationally now and so many other things, air conditioning and increasingly EVs and heat pumps and data centers and computing and everything else are the big drivers.

So yeah, a couple of other things that maybe are to give us again on like a household scale that we're used to interacting with. I mean, one would be a a tank of gasoline in your car. Right in your conventional car. So a gallon of gasoline contains about forty and a half kilowatt hours, forty point five kilowatt hours. So one gallon of gasoline is on that scale of a couple gallons of gasoline, I guess, are on that scale of like average household electricity use over the course of a day.

Now of course you can't turn gasoline directly into electricity at a one for one conversion ratio, right? You gotta use a diesel generator, which itself is only maybe thirty percent efficient. So it actually takes a lot more than that. And and that's also partly why electric motors are so much more efficient, right? At taking that the energy in your battery and converting them into traction in your car is'cause it's already electro electricity. You don't have to combust anything.

To make heat and then drive motion and then turn that motion into power in your wheels, right? There's a lot less heat loss, yeah. Yeah, tons less. Yeah, exactly. So a internal combustion car is maybe a third as efficient as a you know, electric vehicle. So yeah, tank of gas, ten gallon tank of gas.

four hundred ish kilowatt hours. That's actually quite a lot. This is why fossil fuels are so amazing. You can fill ten gallons of gasoline and have an enormous amount of energy from a kind of personal's perspective. Right. I mean it is actually like when you fill up your car's gas tank, let's say it's eight to twelve gallons if relatively It's a lot. Several hundred kilowatt hours. That's your weekly or even more than weeks worth of household electricity.

Right. And also I should think about it it's about a week's worth of commuting too, right? You don't use up Your full gas tank in a day usually, unless you're a Uber driver perhaps. Yeah. So then we so now we're yeah, we're in like weekly scale consumption. Now we're talking about megawatt hours. Whether that's your commute energy usage or your household energy electricity usage.

Then when we talk about gigawatt hours, now we're starting to talk about power plant scale, right? Or data center scale or industrial facility scale. A large nuclear reactor is typically on the scale of about a gigawatt or a billion watt watts. It's a million kilowatt hours or kilowatts. So a gigawatt o a gigawatt scale power plant again producing for an hour.

uh would produce one gigawatt hour of electricity. So when we're in that scale of gigawatt hours, we're talking about the output, the sort of the hour by hour output of a large power plant or a large data center or something of that scale. Those are going to be in in your gigawatt hour term. And then you indicated earlier, terawatts, that's the next scale up, three thousand gigawatt hours is a terawatt hour. Now we're talking about the scale of like annual production for a power plant or

annual consumption for a state or data center or something like that. Those are gonna be on the scale of hundreds of terawatt hours. And nationally we consume about four thousand two hundred terawatt hours of electricity annually in the US So there's now we're in the thousand terawatt hour scale, now we're talking about national annual electricity usage. I think you skipped directly from megawatts to k to from kilowatts to megawatts, but can you briefly talk about megawatts?

Yeah, a megawatt is a thousand kilowatts. So a megawatt hour is a thousand kilowatt hours as well. And then that's again the scale of your weekly electricity consumption in your home or your weekly consumption of gasoline for your community. Or maybe several weeks. Renewables. I mean, I feel like when we talk about solar farms, we're usually talking about in the world of megawatts. So

Um that's true. Most power plants are smaller than a gigawatt. A nuclear plant is big. Most power plants are several tens to hundreds of megawatts scale production. So if they're producing for an hour, then you're in the tens to hundreds of megawatt hours range. But if they're producing for a year, you're more like terawatt hours.

I just want to stick in megawatts for a second because it's actually when we talk about renewables and when we talk about renewable sized additions to the power grid, we tend to be in megawatts. Only when you talk about these giant generating sites. like Vogel units three and four are each, I believe, more than a gigawatt. They're like 1.2 gigawatts or something.

You talk about these massive, massive new nuclear power plants, then we're talking about gigawatts. But mostly in the world of when we talk about adding new power demand, especially from renewables, it tends to be in megawatt hour world. And so just for instance, A technology that we don't hear very much about anymore, concentrated solar thermal.

But that if you've ever flown across the country, I'm just thinking about this because I think it's evocative. When you fly across the country, there are two big concentrated solar plants. These are the mirrors that point at the single tower and then boil things, and when birds fly across, they instantly get Incinerated, but anyway. Um uh

Ivanpa, this famous concentrated solar thermal plant that went up early in the Obama administration and is going to close actually next year. That is three hundred ninety-two megawatts. Yeah, you would see this out your window if you're flying from Exactly. Los Angeles over towards Las Vegas. Exactly. We've had folks from Fervo Energy, the advanced geothermal company, on this podcast.

They're working on applying as we've discussed then. Fervo is the company, one of the several companies that's working on applying fracking techniques to generating clean electricity through drilling new geothermal wells. Cape Station in Beaver County, Utah, their big demonstration project, that's four hundred mega watts. When it's fully built out.

That's gonna be four hundred megawatts when it's fully built out. Empire Wind, which is the big Equinor offshore wind project in New York State, is eight hundred and ten megawatts. And so just to give you a sense, what is the average combined cycle gas? A couple hundred megawatts. Couple hundred megawatts. So just to be clear, like when we talk about power plants, normally we're in this world of talking about megawatts. Anyway though. Yeah. Or hundreds of No.

Or uh another perspective is Princeton University has a gas turbine here that we use to generate some electricity as well as use the waste heat for heating and cooling of the campus. We're gonna shut that down soon and replace it with our ground source geothermal project, but that's a fifteen megawatt turbine.

So for the scale of a single campus, you might have a tens of megawatt scale facility. The data centers, like the big exascale data centers we're talking about, like giant ones, those are usually in the hundreds of megawatts

to even gigawatt scale facilities now that we're talking about some building out three, four, five gigawatt scale campuses for data centers. So that's pretty wild. The other way to think about a gigawatt, I usually think of it in terms of If again, if it's a gigawatt of average consumption, that's like eight hundred thousand homes. So if you assume two people per home on average, that's like a city of one and a half million people scale.

So a gigawatt is a city scale of consumption or production on average. Um which starts to give you the sale of these data centers, right? If it's a gigawatt scale data center, we're talking about like plopping down another w one and a half million people's worth of electricity use with one of those facilities. That's big.

How do you convert? You just kind of did it off the cuff, but often when you see these megawatt, gigawatt numbers, they're immediately followed by a conversion to homes. And I think when you've been paying any attention to this, you realize that these conversions could be like Are especially in PR documents, are like so off the cuff, they're like not comparable at all. What do you think is the best Yeah.

Yes, exactly. And they also vary a lot by region, where like Texas homes use a lot more electricity than homes in the northeast. Yeah, so there's a couple of kind of embedded assumptions there. The most important of which is the average power output of the facility. versus its maximum and then what you assume for how much electricity a household uses. So let's take the Empire Wind project. You said it was eight hundred and ten megawatts. That's its maximum capacity.

Let's assume it's about a fifty percent capacity factor. That's a good average power output ratio for a wind farm. So, you know, wind farms in the Great Plains states on shore, they might be approaching fifty percent capacity factor. Offshore wind, maybe they're in that range, forty to fifty percent. So let's say fifty percent round term, round numbers.

That means it's generating four hundred and five megawatts of power on average. That's pretty big. That's a couple of combined cycle power plants worth all the time cranking out power twenty four seven. So that's a fairly big amount of energy from that wind farm.

But then if we as then we have to assume that the average consumption of a household, which according to EIA nationally is about one point two kilowatts. So if I take that four hundred and five megawatts, that's four hundred and five thousand kilowatts.

of average power output. If I assume the average home uses one point two kilowatts per hour, then that's about three hundred and thirty-seven thousand homes. Call it three hundred and forty thousand in round numbers or three hundred thirty thousand. That's the kind of conversion that's being done behind the scenes when someone is reporting the number of households.

And of course it depends. If I change that capacity factor to forty percent, I get more like two hundred and seventy thousand households, not three hundred and forty. If I take uh maybe a more New York specific household electricity consumption rate, which might be different from the national average, I'm gonna get a totally different number too.

So that's where it gets a little tricky is what are you embedding in there? And I think the best thing to do is just get a feel for the round numbers here. Right. We're talking about Empire Wind is several hundred thousand homes. That's the scale at which it And that's probably as accurate as we can get in these kinds of conversions. Can I ask one more question, which is are homes even the right way to think about this? We always convert to homes, but like

People don't only use electricity at homes. Businesses use electricity. Industrial facilities use electricity. So what's the breakdown of where US power demand goes to homes versus So it looks like just over a bit over a third of US electricity production goes to residential usage. As of twenty twenty two, it was thirty eight point four percent of US electricity sales were to households, residential consumption. That's about equal in size, about thirty five

percent went to commercial buildings, offices and other commercial spaces. And about twenty six percent went to industry. So think of it as like a quarter. going to uh industry. If we all switch to EVs, maybe that's not true. I was gonna say I I think maybe at the uh share of consumption from industry

And commercial properties is gonna go up over time more rapidly than households because of the efficiency gains. But maybe that's not true anymore. We've tapped out the lighting efficiency improvements, like you said, and if we all convert to electric heating and EVs, then actually residential consumption can could grow quite significantly.

So I guess if you're thinking about what's the largest user today, it is the largest sector is residential consumption. So maybe households are the right number to think of. I'm not sure what else. We could use EVs, that would be the other as peop more and more people start to switch to EVs, maybe we'll start to say this'll power however many million EVs for a week or commutes for a week or something like that. That could be the next intuitive thing that we might switch to.

One more question, which is that people what this all means, and I just want to make sure is that when you're looking at say what energy use is for a geographic area or for a system, you have to be careful between maximum use average use. He said this at the beginning, but I want to draw it out. Between maximum use, average use and annual use, because all of those, if I'm understanding correctly, will be in

watt hour, whether it's megawatt or gigawatt. And you just have to be careful that there you don't elide them. I was looking up because I was curious. The New York City subway system uses thirty five hundred megawatt hours annually. So what is that? Three point five gigawatt? Uh So that would be like three and a half nuclear reactors producing continuously for a war. seven natural gas power plants or seven to ten natural gas power plants producing continuously. That's a lot of electricity.

If you think in the household too, it it's interesting to break down like the biggest users, and I think you guys did a good job in your decarbonize your life guide that everybody should check out at Heatmap. pointing out that there are just a few really large consumers of electricity in a typical home that is space heating and cooling. That's the biggest one by far. Coming in at about a quarter that size, or maybe a third, is water heating if you have an electric water heater.

And then even smaller than that is refrigerators. Beyond that, everything else is very small, unless you have an EV, which would be on the scale of your heating and cooling too. Lighting used to be part of that equation, but it's not anymore, as we talked about, because of the growth of LEDs. It's interesting to do this without my lecture slides with a microphone instead. Hopefully that was somewhat helpful.

That was great. This concludes our first session of Shift Key Summer School. We'll be back in the second session with a introduction to how Power plants work. We're gonna go through the history of electricity, starting with coal, to the modern day, describe how each kind of power plant works. We're gonna keep building your understanding of the grid. I'm like delighted we're doing I have already learned so much from this hour. If you hated this, we'll be back with a regular episode of Shift Key.

Sooner than you think. Thanks as always for listening. Shift Key is a production of Heat Map News. Our editors are Gillian Goodman and Nicol Oricella. Multimedia Editing Audio Engineering is by Jacob Lambert and by Nick Woodbury. Our music is by Adam Cromlow. Hope you're having a great summer and see you next week.