Quote Originally Posted by veti View Post
That's why thermostats are set by the people affected by them, not hardwired to a single ideal temperature.
Eh, most thermostats have a fairly small range of settable temperatures, and the "ideal" temperature for people is not that large of a range.
You might find some people that are more comfortable at 65 and others that like 78. And of course you'll find people surviving in a very large range of temperatures. But I don't think I've even seen a temperature control designed for people (as opposed to storage, etc.) that goes below 60 or above 80.

So when you're looking at a heating or cooling system designed for living spaces you have to consider the outside extremes. The cooling requirements for my house in Wyoming, which we've never seen over about 98, and even then it is at most a few hours a day for maybe a week out of the year, is a lot different than a house in Phoenix where the highs are 115-120 and you're lucky to get below 90 during the middle of the night. So a heat pump to cover both of those cases are going to be a lot different. You've also got to consider the extremes, as any system that might get water in it won't be an issue at all in Phoenix where you might see one or two days below freezing and you could keep a line from freezing with a blanket, but that same system in Wyoming would have to be buried 8' deep to keep it from freezing during the winter, which also greatly increases the cost of construction.

And of course heating a house from 30 to 70 is not that hard, but heating to that same house to 60 when you're at -20 is twice as much of a temperature change, so again the same sized system isn't going to work. Throw in increase heat loss from high winds and it gets even worse. And that doesn't matter if you think 30 is cold or not.

Maybe the system is a lot more efficient at cooling than a regular AC system, but it is worse at heating than a furnace. You will clearly come out ahead if you use cooling more. You might come out ahead if you use them similar amount of each, but you're going to be coming out far behind if you're heating a lot more than you're cooling.

It is also very much a matter of cost. If my gas bill averages $50 a month over the course of a year (a lot more during the winter, less during the summer) and I can put in some new system that brings that average down to $40 a month that is a very real 20% decrease in price. But if a new furnace costs me $5000 and retrofitting the entire house to a new system costs me $10000 then that would take me 42 years to pay for.