Why your air conditioning bill is about to soar - the energy required rises with the SQUARE of the temperature differenc

[progree]

Why your air conditioning bill is about to soar , Washington Post, 7/12/24
(no paywall on this MSN-hosted article)
https://www.msn.com/en-us/weather/topstories/why-your-air-conditioning-bill-is-about-to-soar/ar-BB1pRxnN

(summarizing, in my words) Air conditioning costs rise with the SQUARE of the difference between the indoor and outdoor temperatures. e.g. if the indoor setpoint is 75 degrees, then an increase in outdoor temperature of just 4 degrees, from 96 to 100, increases AC cost 42% !. Just for the heat pump aspect of it. Other factors increase that further.

The math: the difference between 75 degrees and 96 degrees is 21 degrees.
The difference between 75 degrees and 100 degrees is 25 degrees
(25/21)^2 = 1.417 => 41.7% increase

Plus more than half the greenhouse gas consequences (and presumably more than half of the electricity cost) comes from dehumidying, which older AC's don't do efficiently. As if that's bad enough, the inability of older AC's to reduce the humidity enough causes people to lower their thermostats to feel comfortable -- yet even more expense and more greenhouse gas emissions.

(No indication of what an "older" A/C is, but mine is about 1968, yes 56 years old, so I know I qualify. But I live in Minneapolis, so I didn't run it at all last year, and so far haven't come close to feeling the need this year -- a fan works just fine. But just about every time I step outside I hear the neighbors' AC's blasting away).

The refrigerants used in AC's also contribute to global warming (they don't quantify)

Couple this with:

How a small rightward shift in the average daily high temperature produces a huge increase in the frequency of very hot days:
e.g. a 2% increase in the July average daily high in a locale with a July average daily high of 85 degrees (e.g. New York City) produces a 2.44 fold increase (144% increase) in the number of 103+ degree July days.
https://www.democraticunderground.com/10143266574#post1

Combine the 2 factors above, and one will find a massive increase in electricity bills (and ghg emissions) for a small shift in average temperature. I'm thinking about how to calculate the combined effect.

More on increased frequency of heat waves:

Heat Waves - decade by decade from the 1960's on - 4 bar charts: Heat Wave Frequency, Heat Wave Duration, ...
https://www.democraticunderground.com/1127174794

[madaboutharry]

1. I was told by a customer service representative from my energy company

that in winter every degree a thermostat is set over 68 degrees increases the monthly bill by 15%. I think that is already a lot.

They have a set temperature and you will increase your bill with each degree change either way with heat or air conditioning.

[NJCher]

2. Fans

I have a late model AC unit, but I use a dehumidifier. Fans in every room. I once read where fans increase the effect of AC because of evaporation and convection. It allows you to keep your AC temp higher.

[Salvador Dolly]

3. Getting hot out? Burn more caol.

Where I live (Chicago) that's mostly how it works, even in a state that is (relatively) big on wind power.

[Shermann]

4. Humid air always takes more energy to cool because of the higher thermal mass.

The good news is that once you reach the point where your air conditioner is running non-stop, any additional rise in outdoor air temperature won't have any effect on energy usage.

[ratchiweenie]

5. So does this apply if you live in an area that is very dry, almost zero humidity?

[CoopersDad]

6. It is really a general scientific principle, every customer will differ.

It's harder to cool wet heavy air, that much is true, but it still costs more per unit of energy due to other factors.

These include time of use rates and the fact that higher demand requires providers to use more expensive sources.

Best to live where no AC is required, where fans and/or evaporative coolers work well.

An evaporative cooler would work very well in a dry climate, if you live in one.

[NJCher]

8. I will add to that

Best to live where no AC is required, where fans and/or evaporative coolers work well.

I live in a forest and that seems to cut temps by about 10 degrees. As soon as I arrive home, I feel the rush of cooler air from the forest.

I have both bamboo and tree forests. The bamboo towers 20' over my house. It also prevents trees from the forest from falling on my house, as it did during Sandy.

[progree]

9. "does this apply if you live in an area that is very dry, almost zero humidity?"

It seems like yes it would. In a near-zero humidity environment, the AC is expending almost no electric energy on dehumidifying, and almost all its energy on pumping heat up a gradient, and that's where the "square law" (electric energy expended proportional to square of temperature difference) applies.

On the other hand, in average or worse locales humidity-wise, and if it's true that half or more of the energy expended is dehumidifying, then the "square law" would apply only to the part used to pump heat up a gradient. As for how the dehumidifying electric energy part changes with temperature or humidity, I have no idea.

So overall, the "square law" probably overstates the impact of increasing temperature on total AC electricity usage.

I should dig into this.

Thanks for bringing up the issue, I was originally thinking the humidity aspect was making it into something more than square until you got me to think about it.

[ratchiweenie]

10. Thanks

I think. Lol.

[hatrack]

7. But!! But!! But!! This is 'Murca!!

What about my right to be free of the laws of physics?!!??!!??