If developing-world nations like Bangladesh start seeing wet bulb temperatures incompatible with life - and we're getting close in spots; https://en.wikipedia.org/wiki/Wet-bulb_temperature#Wet-bulb_... - having to supply AC to tens of millions of people in areas without the electrical infrastructure to reliably run them is... a problem.

An AC unit is a heat pump running in reverse.

So here in the PNW, we typically only heat during the winter. Most people here have never had AC in the summer time. So typically, power usage in the summer here is really low. Most of us just turn off the furnace for a number of months. We know it's fall when we finally turn on the heat.

Now that more and more people are getting heat pumps, I suspect that the energy saved during the winter is going to be offset quite a bit by people running their AC in the summer. I don't know how much that will be, but I know I'll be running my new AC unit this summer. Hopefully I won't need it more than a couple of weeks. But it's been hotter the last few summers, and if the trend continues, we'll be running the AC a lot more.

It's a side effect of building the wrong structure for the environment. If you ever go to the south take note of the architecture in the old homes and even rowhomes where working class people lived. The cielings will be very high, and there will be second window above the doorway perhaps. The windows will have awnings. There will be porches with large overhangs shading living rooms and dining rooms inside the dwelling. All of these features help with cooling a home in a hot climate and making it livable in a world before air conditioning, taking no energy to do so beyond that initial energy investment to build the building itself.

Meanwhile, look at what is built in the south today. The same sort of buildings you might see from alaska to phoenix to orlando to upstate new york. Only they might have installed central air for that floorplan in phoenix or orlando. They aren't building structures fit for the particular environment, they are building structures that are cheap to build in the market and don't really fit too well anywhere, and shoehorning it into whatever environment it sits with AC.

Building with classic Southern US techniques doesn't negate or even significantly reduce the need for air conditioning. Without AC, these types of structures still become incredibly hot during the summer; they suffer from mold and material damage from humidity; they required workarounds like sleeping on a screened-in porch during the summer instead of inside the house, because the house itself was too sweltering to tolerate, even at night. If you were lucky enough not to be laboring outside in the South during the summer, you spent a large part of your day sitting around being miserable. It was a major contributor to the south's lag in economic development, and a strong contributor to historically poor public health and life expectancy.

They're also not particularly efficient in terms of space utilization, making them unfeasible for sustainable, 'walkable' neighborhood development.

At least now adays modern structures are starting to incorporate these sorts of built in cooling solutions (e.g. sun shades) but I think there is a good middle ground to be struck between the 1850s and building structures that require less energy to cool in the first place. A lot of this stuff is just simple physics at work; hot air moves up etc.

Recently in CA in my neighborhood, someone decided to paint their spanish style home dark brown. I can't help but think going from ivory white to dark brown is going to increase their AC bill in the summer. Just using basic physics with consideration to the environment can go a long way.

Heat pump and AC unit are two names for the same thing.