this post was submitted on 30 Mar 2025

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254

Power is not energy: why the difference matters [Technology Connections] (www.youtube.com)

submitted 4 days ago by [email protected] to c/[email protected]

38 comments fedilink hide all child comments

So, Alec over the Technology Connections channel made an hour long video explaining the difference with kW and kWh (obviously with other stuff around it).

I'm living in northern Europe in an old house, with pretty much only electric appliances for everything. We do have a wood stove and oven, but absolute majority of our energy consumption is electricity. Roughly 24 000 kWh per year.

And, while eveything he brings up makes absolute sense, it seems like a moot point. In here absolutely everyone knows this stuff and it's all just common knowledge. Today we went into sauna and just turned a knob to fire up the 6,5kW heaters inside the stove and doing that also triggered a contactor to disengage some of the floor heating so that the thing doesn't overload the circuit. And the old house we live in pulls 3-4kW from the grid during the winter just to keep inside nice and warm. And that's with heat pumps, we have a mini-split units both on the house and in the garage. And I also have 9kW pure electric construction heater around to provide excess heat in case the cheap minisiplit in garage freezes up and needs more heat to thaw the outside unit.

And kW and kWh are still commony used measurement if you don't use electricity. Diesel or propane heaters have labels on them on how many watts they can output right next to the fuel consumption per hour and so on. So I'm just wondering if this is really any new information for anyone.

I assume here's a lot of people from the US and other countries with gas grid (which we don't really have around here), is it really so that your Joe Average can't tell the difference between 1kWh of heat produced by gas compared to electricity? I get that pricing for different power sources may differ, but it's still watt-hours coming out of the grid. Optimizing their usage may obviously be worth the effort, but it's got nothing to do with power consumption.

So, please help me understand the situation a bit more in depth.

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[–] [email protected] 74 points 4 days ago (2 children)

If you think the average person understands watts, you live in a bubble, straight and simple. You have a very skewed notion of the average person.

[–] [email protected] 11 points 3 days ago (2 children)

Yep that video is leagues beyond most peoples capabilities to understand. Thinking they already knew and understood it is crazy.

[–] [email protected] 5 points 3 days ago

Explaining to people learning to cook that oil is liquid pan that carries heat is just too mind blowing. The simple shit is wayyyyyyyyyyyyyyyyyyyyyyyyyyyyy beyond the average smartwatch wearing doof

[–] [email protected] 3 points 3 days ago* (last edited 3 days ago)

Nah, the video is pretty straightforward, but it's presented in a way that most people would lose interest unless they're actually into the subject matter. I see three problems with the video:

it's too long
very few analogies
mostly a talking head

Power vs energy is fairly simple with a good explanation. Power is simply the speed at which energy gets used up. For example:

if you make a big campfire, it'll use up your wood (energy) faster
if you're playing games on your phone, your battery (energy) will die sooner
if you sprint, you'll use up your energy faster than if you jog

That's extremely intuitive. All a regular person needs to know is that simple concept, plus a way to measure it (the Kill-a-watt example). Boom, 5-10 min video.

But the talking head made it way more complicated by starting with gas. That's just belabouring the point that you can increase or decrease power, which is already intuitive with batteries or things we can see (wood) or feel (tiredness).

They could then segue into gas, once the power vs energy issue is established. A can of butane is like a battery, and the valve (e.g. screen brightness, game vs texting) controls how quickly it's used. We can compare gas and electricity directly because electricity can be turned directly into heat, just like gas can.

And then you segue into heat pumps. Basically explain how your AC/fridge works (i.e. moves heat instead of creating "cold"). Make a demo where you move heat vs create heat and show how much energy is used. As in, heat a room from 72F or whatever to 90F, one using a heat pump and the other using a space heater. Show how temps compare on both sides of the heat pump vs space heater (other rooms shouldn't change w/ space heater). Then use that to show a real-world example of a house that swapped from furnace to heat pump to really drive the point home that moving heat is more efficient than creating it.

[–] [email protected] 2 points 3 days ago (1 children)

We live in a world where people demanded (and succeeded) in having the Meteorological Service of Canada to report windchill as "feels like C" instead of, ya know, a measure of actual heat loss in Watts / M^2 / s

[–] [email protected] 3 points 3 days ago (2 children)

You say that like it’s a bad thing? I prefer not to dust off my slide rule everytime I want to know how cold it is out.

[–] [email protected] 2 points 3 days ago

Yeah, just give me actual temp and wind speed, and I'll get a feel for what's cold by going outside.

[–] [email protected] 1 points 3 days ago

The first time they did the feels like scale... My father's colleagues were involved. They took a sample of people and put them in wind tunnels and sprayed them with water and said hey how's it going over there.

I wish more than anything I was joking right now.

[–] [email protected] 83 points 4 days ago

I think you are greatly overestimating the basic functional knowledge of the general public...

[–] [email protected] 37 points 4 days ago

In here absolutely everyone knows this stuff and it's all just common knowledge.

Absolutely not. Not even close.

[–] [email protected] 40 points 4 days ago (1 children)

New Technology connections video drops:

I'm going to go buy a kill-a-watt.

[–] [email protected] 3 points 3 days ago

Do it, it teaches you things.

Most of your power isn't going where you think.

[–] [email protected] 24 points 3 days ago

65 wat

[–] [email protected] 19 points 3 days ago (1 children)

Follow-up video idea: speed ≠ distance

[–] [email protected] 9 points 3 days ago (1 children)

The one that I think more people misunderstand is temperature Vs heat Vs something feeling hot/cold. One is a property, one is energy, and the other is the transfer of energy.

[–] [email protected] 2 points 3 days ago

You know a nation of people who may not be able to articulate their understanding, but definitely have a high intuitive understanding of that?

We Finns.

100C sauna and no problem sitting on wood, but happen to touch something metal and oooh-weee.

Also same thing happens the others way around when it's - 20c outside. I don't think there's many people in Finland who don't have a core memory of what cold metal tastes like in winter, because of the resulting trauma. And it doesn't even need to be metal to stick.

Nicely explained.

[–] [email protected] 29 points 4 days ago

haven't seen it so far, but technology connections will always get an upvote.

also consider subscribing to his channel, his videos are amazing.

[–] [email protected] 25 points 4 days ago* (last edited 4 days ago) (2 children)

lot of people from the US with gas grid (which we don’t really have around here), is it really so that your Joe Average can’t tell the difference between 1kWh of heat produced by gas compared to electricity

Right, because for most people gas is metered and sold by the CCF, and not converted into kW at any point in the chain.

So I know i used 30ccf last month, but there's zero indication what that is in kW, because we usually don't convert between the meter (which is volumetric) and the billing, which could be anything but why bother?

[–] [email protected] 11 points 4 days ago

Reticulated gas is charged by the kWh here in New Zealand. The meter may well be calibrated in m³ (I don't have gas at home, so I don't know for sure) but all pricing is energy, not volume.

For bonus points, if instead you buy your gas in cylinders - a pair of 45kg (~100lb) cylinders is a common installation for houses without piped gas - those are sold simply by the unit. The best conversion for that I can find is one energy retailer describing one 45kg cylinder as 2200MJ (611kWh).

I expect this is one of those things that is overall horribly inconsistent depending on where you live.

[–] [email protected] 6 points 4 days ago (1 children)

Also from Europe, gas is measured/billed in kWh here as well.

[–] [email protected] 1 points 3 days ago

Not everywhere, in Lithuania they charge per m³.

[–] [email protected] 19 points 4 days ago (1 children)

Power is water throughput in a pipe, energy is water filling a bucket. Simplest way I've found to explain it in my 15 years in the energy space.

[–] [email protected] 3 points 3 days ago (1 children)

Power is a measurement of the velocity and volume of water flowing through a pipe at a given instant*

I'm so sorry, I am officially 'that guy', taking a simple analogy and making it annoying...

[–] [email protected] 1 points 3 days ago

Lol you're completely right of course but when you start adding all this it is less relatable to someone who is not familiar with it already

[–] [email protected] 22 points 4 days ago* (last edited 4 days ago)

is it really so that your Joe Average can’t tell the difference between 1kWh of heat produced by gas compared to electricity?

Yup.

I totally understand electricity because it's pretty intuitive. Everything is advertised in watts, my bill comes as kilowatt hours, so it's pretty easy to calculate how much energy something uses by plugging in a kill-a-watt and measuring it.

My gas is billed in therms. I don't really know what that is, nor do I know what the flow rate is for my furnace or gas stove, so I have no concept for how much energy I'm using. I don't have an electric one to compare with, so I that's not an option either. So how exactly would I get to the point where I would be able to compare the two without a lot of annoying testing? Even then it would be extremely imprecise.

And no, it's not "watt hours coming out of the grid," except in the pedantic sense that they can be converted. They come from very different sources, so it's like comparing an EV to a horse, and while you could, it's completely nonsensical.

But yes, at some base level your average American knows there's a connection between the two (after all, I can choose between electric heat/heat pump and a gas furnace), but they'd rely on an expert to estimate the monthly price difference between options, since that's ultimately what we care about. The problem is mentioned near the end of the video, HVAC experts don't seem that familiar w/ heat pumps, so you may not get a decent estimate, depending on who your technician is. And that adds to the misinformation.

[–] [email protected] 9 points 3 days ago (1 children)

There's no way even 1% of people understand this in the world. Maybe 1% know of those measurements "existence" asking them what they are would get an "uhh"

[–] [email protected] 3 points 3 days ago (1 children)

In the world? Me and millions of other people got this info in middle school physics. Sure, maybe we mostly forgot the details by now. But it's not arcane or ancient knowledge lost to time. It's in your electricity bill every month. A quick visit to Wikipedia and I got the gist of it back. Every single physicist, engineer, and electrician got this explained again to them.

[–] [email protected] 1 points 3 days ago* (last edited 3 days ago)

It’s in your electricity bill every month.

You get a comparison of electric vs natural gas flow in your energy bill? Wow!!

I think most people understand W vs kWh, at least on some level. They know things use different amounts of energy depending on what it's doing (i.e. a microwave sitting idle vs actually warming things), but they may not be comfortable estimating kWh from watts.

But that's only the first part of what OP talked about. The meat of the discussion was about energy stored in something like natural gas vs electrical energy. How exactly am I supposed to compare a gas furnace and electric AC vs an electric heat pump? Not only would I need to somehow convert therms (or whatever local unit you use for gas energy) to kWh, but I also need to understand efficiency of heat transfer for heat pumps, which will vary quite a bit based on the weather (much less effective in cold weather).

That's complicated, and many HVAC professionals here don't like heat pumps for whatever reason so they tend to think in terms of resistive heating vs gas heating, which is absolutely wrong. I want a good idea of cost difference between gas furnace + electric AC vs a heat pump, but that's not something I have easy access to.

[–] [email protected] 13 points 4 days ago

I sometimes make a conscious effort to understand electricity. For a few days, I then think I understand what's going on and then promptly I forget.

(Yes, I shall watch this video.)

[–] [email protected] -1 points 2 days ago

People complaining about this video have clearly not watched much Technology Connections; I enjoyed it immensely. It's right in line with how Alec normally does his videos. We who are loyal to the Great Alec expect the pedantic content.

[–] [email protected] 5 points 3 days ago

He’s making a point about instantaneous versus overall energy use, which it sounds like you already understand. “Power” and “energy” are already kind of loose terms, which could make that conversation confusing IMO.

But for anyone confused by this:

For the typical energy consumer, Watts (W, kW) are relevant when considering circuit capacity. Otherwise, Watt-hours (Wh, kWh) is likely the metric you’re looking for when considering energy use.

Concretely, your coffee maker might pull 1.2 kW while in use, more than most appliances in your house, yet it probably represents a minuscule portion of your electric bill, perhaps less than 1 kWh, since it only needs to boil a small amount of water with each use.

[–] [email protected] 4 points 3 days ago

After watching the video it was a bit over explained. I think he got his point across in the first 10 minutes, though I am an engineer by trade.

I appreciate his rigour in explaining and it is a good refresher on the power/energy calculations.

[–] [email protected] 4 points 3 days ago (1 children)

is it really so that your Joe Average can’t tell the difference between 1kWh of heat produced by gas compared to electricity?

Most people don't even know what a watt or watt/hour is. And have no idea how energy from gas relates to energy from electricity.

[–] [email protected] 4 points 3 days ago (1 children)

watt/hour

Oh yeah I've seen that used before, makes me cringe every time.

Anyway, do must people not go to high school? Or is stuff like that not part of the physics curriculum in some places?

[–] [email protected] 3 points 3 days ago (1 children)

In my highschool physics was optional. You had multiple options for science credits and could get through without taking it.

[–] [email protected] 0 points 3 days ago (1 children)

Oh, in my country you have to take physics, chemistry and biology. That actually goes for middle school too. Plus geography which actually also contains geology. And math could be considered science I guess.

We have elective courses too, but all the basics are mandatory. That includes at least two foreign languages, history, our own language, literature (becomes separate subject from language in high school), music, art (including history of both), basic computer usage, shop class for boys and home ec for girls (with trades in between so us boys still got to cook and stuff, plus in elementary school everyone gets to knit and crochet IIRC). Oh and physical education unless you're disabled, in which case you either get to watch or just do something else I think.

I'm actually sure I've missed something. These are all mandatory. You can do shit like folkdance or choir for electives, or many other things depending on school. I had philosophy as one of my electives lol

I think people in some countries (the US) don't even know what they're missing out on tbh.

[–] [email protected] 1 points 3 days ago

I never took chemistry, and I didn't take a real physics course until college, though we had survey courses like "physical science" throughout school.

I don't recall if we talked about watt hours specifically, but joules were certainly mentioned, though I doubt most people remember it. Most of the emphasis was on things like friction equations (given an ideal pulley and an incline with slope...), not real world things like understanding your electricity bill.

That said, I think most people intuitively understand the difference between instantaneous consumption and total consumption over a time period. They know playing games will drain their phone or laptop battery way faster than browsing the web, for example. They just tend to not stop and think about it and they simplify things in the wrong way (power rating on device), though a total energy estimate does work (e.g. when comparing refrigerators).

[–] [email protected] 4 points 4 days ago

Full disclosure, I didn't watch the video yet, but it's likely a difference of environmental impact.

He's described in previous videos how burning gas at home is less efficient from the standpoint of a carbon footprint. I imagine this video is to help explain everything in a way that helps you come to that conclusion yourself. Teach a man to fish instead of just giving a fish and what not. So you can apply the knowledge to other things in your life