Environmentalists and the green building world used to despise air conditioning. Back in 2006, William Saletan nailed it in an article in Slate:
Fifteen years later, that "part that's still habitable" has diminished significantly. But the air conditioner has become acceptable, having been re-branded; it's now called a heat pump. The air is still being conditioned, but by reversing the cycle, it can heat as well as cool. It is still an air conditioner, it's still sucking electricity. But a lot of smart people are claiming that because it can heat without gas, it can help eliminate carbon dioxide emissions if it runs on zero-carbon electricity. That's why environmental writer David Roberts is tweeting:
Roberts was the first to use the phrase "electrify everything" when he wrote for Vox, noting that it was the second step after "clean up electricity." He points to an article in Quartz titled "Want to cool your home, save money, and curb climate change? Try a heat pump." But are any of these claims true?
Sure, it's an air conditioner.
Not in summer—it's an air conditioner. It won't cost any less to run than a unit that only cools. It will save money in winter if you have electric resistance heating. It conditions the air by pumping heat from the outside to the inside, which takes about a third of the energy than making heat directly from electricity.
If you are converting from gas, it depends. Roberts lives in Seattle, where electricity costs 7.75 cents per kilowatt-hour, which is really cheap. Natural gas costs $1.19 per therm, which converts to 4.02 cents per kilowatt-hour. Seattle doesn't get too cold, so the coefficient of performance (COP) of the heat pump (the ratio of efficiency compared to straight resistance heating) isn't going to drop too low; let's say it stays at 3, so running the heat pump is Seattle is going to cost 2.58 cents per kilowatt-hour, which is less than gas. And the warmer Seattle gets, the better it performs.
But move inland a bit where it gets colder, and the efficiency of the heat pump drops considerably. Go to where the electricity is more expensive (It's double in New York or Toronto) and gas will be cheaper. In Toronto, with clean but really expensive electricity, it will cost at least twice as much.
Also, if you are going from a house that never had air conditioning (which in the temperate Northwest, was common) your electricity bill is going to go way up; people who have central air tend to use it, and not just in the heat waves, they get acclimatized to it.
In Seattle, where the electricity is probably the cleanest in the country, the answer is an unequivocal yes: You are switching from fossil fuel to carbon-free hydroelectric (84%), nuclear, and wind, so going electric will significantly reduce CO2 emissions. In other parts of the country where electricity is made with natural gas and coal, less so. Everyone likes to point out that the grid is getting cleaner, but now we are talking about adding piles of new heat pumps to it.
This tweet from Saul Griffith demonstrates my concern: 90% of those air conditioners are being sold in Asia and Africa, where they are being bought for cooling only. Whether they have "heat pump technology" by which I suppose he means the ability to pump heat in both directions, is irrelevant. They are being bought by an expanding middle class desperate to not die in a warming world, increasing the need for electricity which is supplied by building more coal-fired power plants, a vicious cycle where more heat pumping leads to more global heating. Yet somehow saying "those better have heat pump technology!" makes them magically different, which they are not.
This is why I am so frustrated by this "fist pumps for heat pumps" thing. When Saletan wrote his article 15 years ago, everyone talked about energy and efficiency. But with climate change, the problem is carbon, and energy doesn't equal carbon. So as Roberts noted, if we clean up electricity and "electrify everything," efficiency is not as important. Some, like Griffith, go so far as to suggest it doesn't even matter.
There is a seductive logic to it. We have a carbon crisis now, not an energy crisis, and driving an electric car to an electrically heated and cooled house using carbon-free electricity neatly solves it all, and nobody has to give anything up. As Elon Musk likes to say, it is the future we want.
But we also have a cooling crisis. Almost everyone in North America is now ordering up air conditioning, the world is getting hotter and AC has gone from being a luxury to a necessity.
That's why almost a decade ago, after years of writing about how we should learn from Grandma's house, with its porches, cross-ventilation, and high ceilings, I threw in the towel and switched to the idea of Passive House, where you super-insulate and seal and shade. If air conditioning is inevitable, then you want to design buildings that consume as little energy for heating or cooling as possible. Is it still relevant in an electrify everything world where carbon, not energy, is the issue? I would say yes, for a number of reasons.
Conventional heat pumps are charged with fluorinated gases that have global warming potentials (GWP) that are thousands of times that of carbon dioxide. There are a lot of leakages; a United Kingdom study estimates that about 10% of installations leak each year. The study notes: "As a result, the GHG emissions associated with refrigerant use will be increasingly important as deployment of heat pumps grows." However, small heat pumps can be charged with R-290, which is good old propane, with a GWP of 3. For safety reasons their size is limited, but in a small Passivhaus design, that is more than enough.
Also, heat pumps do not give you resilience or security when the power goes out, and with the American grid in the shape it is, the more heat pumps we have, the more likely the power will go out.
The vast majority of the residential electricity consumption in the U.S. is now heat pumping for cooling (sorry, air conditioning). After this year's heat waves, it will increase dramatically; that yellow band is going to get a lot fatter. That's why we have to still focus on efficiency and reduce demand. Imagine how many solar panels and wind turbines are needed to change that blue natural gas band to yellow. Imagine how happy everyone will be after installing their new heat pump and then getting told they have to turn it down or off. Or when the gas peaker plants turn on and start spewing CO2, eating up all those carbon savings. That's why we have to build resilience; imagine how useless it will be when the power goes out.
I do agree that we have to electrify everything, and we have to eliminate fossil fuels as quickly as possible. But let's get real about this; we have done wonderful things so far with solar and wind, but nuclear and hydro are not growing. For the electrify everything concept to work, we have to replace that blue gas line with renewables. If everyone goes "Team Heat Pump" and ignores efficiency, the peak loads in summer are going to explode. It will be worse in winter when those solar panels are generating less, and the backup toaster coils kick in because the heat pumps can't pull any more heat out of the cold air.
We can add solar panels and wind turbines as fast as possible, but can we outrun the increase in demand for electricity? Perhaps eventually, but right now, according to the U.S. Energy Information Administration, the average emissions across the U.S. are .92 pounds of CO2 per kilowatt-hour. Natural gas puts out .40 pounds of CO2 per kilowatt-hour, so a heat pump with a winter COP any lower than 2.3 is worse than gas. For heat pumps to make any difference, not only does all of the expanded demand for electricity have to be carbon-free, but we have to rapidly decarbonize the entire existing power supply, which is designed to meet not our everyday needs, but the peak daily and seasonal loads. And how do you reduce peak loads? With efficiency.
That's why reducing demand for heating and cooling with insulation, sealing and shading is still important. That's why I am still promoting Passivhaus. That's why we still need efficient multifamily housing with fewer exterior walls, in walkable 15-minute cities: to reduce that demand which will come from our homes, offices, and cars in an all-electric world. Otherwise, this is all just academic.
As Saletan wrote 15 years ago about more people buying air conditioning, "The hotter it gets, the more energy we burn." That hasn't changed. Rebranding air conditioners as heat pumps don't change much either, other than making some people feel less guilty about buying them. They have to be paired with a reduction in demand for electricity if we are going to be able to supply everyone with carbon-free power, which we have to do if we are going to deal with the root cause of the heat waves that are driving everyone to buy them in the first place.
Fourteen years ago, Barbara Flanagan wrote: "What happens when humans treat themselves like dairy products chilled behind glass? Civilization declines." And look at our civilization now; apocalyptic heat, the air full of smoke, we are talking about hiding in refrigerated bubbles behind HEPA filters, and environmentalists are saying that reversible air conditioners will save us. They won't.
So no fist pumps for heat pumps from me.