The key there is “once the generation system is in place.” If you’re using electric resistance heating (typically that’s what “electric furnace” means), instead of a heat pump, then you need WAY more solar panels, turbines, etc. to power it. That makes the upfront cost of the generation system cost more than the difference between a cheap electric furnace and a heat pump. There’s a similar factor with ground source heat pumps. While the equipment itself is a bit more expensive (pumps, antifreeze tanks, water-to-water heat exchangers), the main cost is in the ground loop, whether trenched or drilled. For those systems, it’s often much more cost effective upfront (and bonus, down the road too), even in remodeling projects, to improve the building’s insulation. That reduces the number of wells or trenching, and it needs lower capacity equipment.
They’ve been around far longer than that, being used for heating as far back as the 50s. But they weren’t more commonly used for heating/cooling until the 70s, which is when I first heard about them in an AC training class.
A tradeoff, depending on personal preference and how your home is set up, is that you now have cooler air blowing on you than you would with a hotter source. I get cold when our heat kicks on.
I recall anti-heat-pump radio advertisements that stations in Detroit were running. About – 40 years ago.
The advertisement had a character doing a “W.C. Fields” circus pitchman’s voice: “The heat pump, the heat pump, the wonderful heat pump.” Then a child’s voice would ask questions like “Doesn’t the heat pump still need a backup furnace?”. And the pitchman wouldn’t have an answer.
So there was some group actively pushing back on heat pumps.
I’ve used a heat pump for 15 years, in conjunction with an electric furnace, and I’m a big fan. The furnace is necessary as we often have long, cold winters and the heat pump isn’t very effective below freezing. Ours has a sensor & when the outside temp is below 32F the heat pump doesn’t run, the furnace does it all. I don’t know how much money it saves since I’ve never done a direct comparison with running the furnace, but I suspect it’s a lot since the operating part of a heat pump is a fan, which is cheaper to run than heating an element in the furnace. And I don’t know if it saves enough to cover the upfront cost of the heat pump – which depends on the size of your home. My favorite thing about the heat pump is the cooler air means the humidity stays at a reasonable level & that awful winter-drying-out doesn’t happen. But older people may find the cooler air uncomfortable & prefer the hotter air from a furnace.
One point I’d like to raise:
When my wife and I built our last house, we insulated it to the gills and put in the highest AFUE and SEER furnace and a/c system that we could get.
My bet on energy prices has always been bullish: it ain’t getting any cheaper.
If you can wrap high-efficiency components into your mortgage, and you can afford the upgrades, it often makes sense. If you have the cash and increasing your cost basis does anything for you, it may make sense.
Bear in mind that most of these things still don’t translate well to resale value. That may change over time.
But energy gets cheap in this country and ‘we’ buy 700HP Dodge Hellcats and 6000# GVWR trucks that get horrible mileage. Once we do, the price of gas inexplicably goes way up (/s).
I view energy efficiency as a hedge against almost inevitable inflation. And the Carrier Infinity system in my last house was basically silent and always maintained our home at the setpoint to within about 0.3*F.
And the Rockies aren’t exactly famous for a temperate climate.
So the economics were great but the comfort factor was the home run swing.
When people are looking at these sorts of cash expenses, it’s good to play with what you think the long-term trend of energy costs might be. Suddenly, some things make sense.
I clearly don’t understand heat pumps (although I’ve had one in every house I’ve lived in since mid 1970s)
The “internet” says they heat a house by taking heat from the outside air, “even cold air” and bringing it inside.
If it’s 35 degrees outside and 65 degrees inside, and I want to raise it to 67 degrees, how is taking 35 degree air going to help?
Does your refrigerator exhaust warm air from the back?
Yes?
That’s because it is taking heat from the cold insides, making them colder, and moving that heat to the outside.
ETA: This is possible because the refrigerant boils at a very low temperature. So, it takes energy from the surrounding area even if it’s pretty cold.
An air-source heat pump uses the basic refrigeration cycle for both heating and cooling.
If you understand how a refrigerator or an air conditioner works, you understand how a heat pump warms a home.
The way the technology works is it can extra usable heat energy from the air down to pretty low temperatures, there is obviously a limit. Apparently right now the highest end models can still perform this down to -35C, but that is not typical for home units. Most home units installed in the 80s/90/early 00s generally could work down to around freezing, newer models can work to around 0F/-17C or so.
It does the same thing your fridge (or A/C) does. In your fridge sub 40 degree air heats the refrigerating coils, the working medium is then compressed, which raises the temperature, without adding much energy to a temperature above your indoor temperature. The working medium condenses in the coils at the back of your fridge, dumping energy into your house, and then passes through an expansion valve which lowers the pressure, and thus the boiling point and temperature, of the working medium, before it goes into the refrigerating coils again. The low pressure, low temperature, preferably liquid, working medium then evaporates in the refrigerating coils, and on it goes.
Thanks. I think we found the problem 
I guess it’s one of those things I don’t need to wrap my head around.
I see what you did there.
It’s not about taking air from outside. It’s about taking the heat from the outside air. Most of the air itself stays where it is.
We finished our new home a year ago. I really wanted to do a ground-source heat pump and not have any propane on site at all, but the numbers we got were insane. Like $30-50k more and we have very easy digging conditions. I expect we’ll make the change if/when the boiler takes a dump. However, our last rental had a GSHP and our landlord said the resistance heat coil kicked on quite a bit and his electricity bill was pretty high. We use maybe 100 gallons of propane a month (Montana). Doesn’t seem like it’s truly mature yet.
Interestingly, my clothes drier uses both sides of a heat pump for operation. As anyone who has stood next to a window AC unit knows, hot air comes out the back and cold air is coming out the front.
In my drier, the “cold” side condenses water from the hot, humid air being blown past the wet clothes. That air then moves to the backside heat exchanger and gets warmed up. That warm air is piped back into the drier and the cycle continues.
There is no exhaust pipe sending the hot air outside. It just keeps recycling the air inside the drier.
Pretty cool really. It also works on a normal, 120v outlet. Nice and efficient.
It’s plenty mature. That sounds like a case of either bad programming in the controls or a shady contractor who undersized the well field to get a low bid. Every project I’ve worked on with ground source heat pumps (dating back to 2005) doesn’t have any resistance heaters at all because they don’t need it (especially so if heating and cooling seasons are roughly equal, like in the Ohio Valley).
Well, this is Montana. Not as cold as it used to be, but we saw -29 last winter once. We talked to companies who specialize in GSHP and still saw crazy prices for install.
Do they itemize the costs?
You can rent a 48" trencher from Home Depot for $180/day. I do not know if that is deep enough (and, of course, you need to be crystal clear you will not trench through a pipe or cable) but seems an inexpensive way to deal with a big cost of installation.
Or is that just something a professional really needs to do for you?
Many tens of thousands of dollars is just what well fields cost. Horizontal trenches are a bit cheaper but the farther north you go the deeper they have to be, and you’re tearing up a LOT of your property to do that. Around here it’s typical to do roughly one vertical well 150’ deep per ton of system capacity. So a normal sized but well-insulated house would probably have four or five wells spaced 20’ apart. That’s a lot of work for a drilling rig and you still need trenches to connect them all and get them to the house.
But air temp doesn’t matter for a ground-source heat pump. I don’t imagine below the frost line the ground’s going to be less than 50-F and that’s plenty of heat to work well.