> what it’s going to take, from the human side of the equation, to make heat pumps the obvious, accessible, and default choice for millions of American homes.
Well, this has already happened; living in a third-world American country, I've been heating my houses in winter with heat pumps every winter for many years (even though they iced up occasionally) and most air conditioners here are already heat pumps. Frio/calor, they're called.
But, installations strictly for heating are probably never going to happen en masse. In https://news.ycombinator.com/item?id=45698730 I analyze the costs. It turns out that heat pumps cost around 39¢ per peak watt they save, while low-cost solar panels cost 6.5¢ per peak watt they produce, so it's almost always cheaper to install enough solar panels to heat your house resistively. And that gap is going to continue widening for the foreseeable future.
Our heat pump, a cheap-shit Electrolux mini split assembled in Tierra del Fuego, broke down last winter; somehow the refrigerant escaped. The repairman did a pressure test with nitrogen but couldn't find a link. He pre-emptively soldered shut a pipe that had been crimped shut at the factory, and pointed out that, probably, if we hadn't been using it as a heat pump, it would have been fine. Certainly it would have had many fewer hours of operation. We ended up spending about US$100 on the repair, which is the price of 1500 peak watts of solar panels. I think that brings us to about US$500 total spent on the thing—insignificant to people in the US, but a significant chunk of change in most of the rest of America.
Heat pumps are an energy-crisis-era efficiency measure to conserve energy. But energy is no longer scarce. After 50 years, the energy crisis is, if not ended, at least ending. If your house's solar panels are producing more energy than you can use or sell back to the grid at a decent price, the energy to run a resistive heater is free.
> But, installations strictly for heating are probably never going to happen en masse. In https://news.ycombinator.com/item?id=45698730 I analyze the costs. It turns out that heat pumps cost around 39¢ per peak watt they save, while low-cost solar panels cost 6.5¢ per peak watt they produce, so it's almost always cheaper to install enough solar panels to heat your house resistively. And that gap is going to continue widening for the foreseeable future.
My counter-scenario: My utility provider wants ~$40k to upgrade my home service to 200 amp, so the up-front cost of electric resistive heat would include that.
Either that or solar panels, yeah. I mean it sounds like US utilities are doing a pretty bad job of delivering the unprecedentedly cheap solar power of the last three years to their customers in any case. They're still acting like we're in an energy crisis! So you have to install the modules yourself.
A normal solar panel install wouldn't let me move to resistive heating regardless of size, my house simply isn't serviced with enough amperage. My gas furnace is 100k BTU give-or-take, so I'd need >100 amps for heating alone.
Yes, 100kBTU/hour, which I assume is what you mean, is 29kW, which would be 133 amps at 220 volts, or 610 amps at 48 volts. But solar only supplies power intermittently; you'd need to draw much more power than that when the sun was shining to blast your mansion with 29 scorching kilowatts around the clock. Maybe 100kW, about 2000 amps at 48 volts. For that you'd need ten parallel #0 wires (8.3-mm-diameter copper bars) or the equivalent amount of copper divided among more wires. If it's running four stories from the parapets of your sprawling castle down to the physical plant in the basement, say 16 meters because of all the vaulted ceilings, we're talking about 160 meters of #0 wire, 76 kg of copper.
That's US$833 of copper, and probably US$2000 worth of wire, but it's also US$12000 of solar modules at current international wholesale prices. So the wiring is kind of the least of your worries!
But there's no need to get 2000-amp service from the electrical utility.
Er, yeah, the math there looks right, but my point is that with a non-exotic solar setup, I can't supply more amperage to my house via solar than what my grid connection allows... though actually looking at how the ratings work, solar capacity is going to be limited by the busbar rather than the grid connection... so I could upgrade my panel to 200A, keep 100A service and get maybe 80A of solar capacity at the max if I got around the solar sizing limits... which, as we've both noted, isn't enough to heat my house resistively.
While your description was funny, my house isn't especially palatial - it's a pretty bog-standard <2000 sqft house from the 70's with new windows and attic insulation. Unfortunately, the insulation can't otherwise be upgraded much without extension/expensive renovations, and it just takes a lot of energy to keep it heated when it's -35° outside.
Yeah, I agree. I have the advantage of living in a subtropical climate, which seems like less of an advantage when the dengue season hits, but the 3400W heat pump my wife and I bought last year does a fine job of heating our 18m² bedroom—and, far more importantly, cooling it when it's +35° outside. You, by contrast, have apparently bought a palace somewhere closer to Antarctica.
200m² of solar PV can only provide about 45kW peak anyway, and on the roof under two meters of snow it would provide roughly zero. One of the advantages of vertical panels like Joey Hess's system discussed here the other day is that they don't necessarily get snowed on, and in some orientations they produce the most energy in the winter. But without enough insulation there's a limit to what you can do. This was apparently a major reason for hanging tapestries in castles older than yours.
Every solar setup ten years from now is going to look exotic by our current standards. Think about automobiles before and after the Model T, or shipping before and after the steam locomotive.
If I was contemplating heating a mansion on Hoth with 2000 amps of low-voltage DC from solar panels, I don't think I would want it connected to a single busbar. I think I'd want it in 5–40 separate circuits to limit the risks from possible short circuits.
Remember: The season that you need heat is the season with the least sunshine. Solar is only cheap as you claim due to net metering; without pairing it with batteries or some other form of storage, you're pushing your heating cost on others by flooding the grid with electricity when it isn't needed.
Now, I will gladly point out that I have a roof of solar panels, and benefit from subsidies: It's important to understand that solar currently is unsustainable economically and will only be sustainable with more R&D on storage.
No, I'm not talking about net metering, which has nothing to do with the cost per peak watt.
You're right that you do need energy storage, though. Even sensible-heat thermal energy storage is completely adequate for this purpose, and it's very cheap, on the order of US$2–3/kWh. See the sand-battery outline I wrote yesterday in https://news.ycombinator.com/item?id=45690085. Electric night storage heaters are widely available off the shelf in many countries already, though not in the US.
For some other kinds of energy storage, it's debatable whether utility-scale storage or household-scale storage is more efficient; you're trading off economies of scale against transmission and distribution losses and transaction costs. But low-grade thermal energy storage is clearly better at household or neighborhood scale; my design outline linked above comes to a price per kWh that's 3% of the price of the batteries needed for BESS, and maybe 15% of the optimistic cost estimates for sodium-ion. You have to reduce the energy to low-grade heat up front to store it so cheaply, but that makes it hard to redistribute later—to redistribute low-grade stored heat from a central energy storage facility, you need something like New York's steam district heating systems. It's far cheaper to store the thermal energy at the point of use.
This is not a new idea. It's the idea behind adobe walls, Russian stoves, rocket mass heaters, electric night storage heaters, dol beds, kachelofens, kangs, earth-bermed walls, Trombe walls, and ondols. People have been doing this for 7000 years, without an electrical grid or, for that matter, electrical power at all. It definitely doesn't rely on net metering!
This looks like something that needs to be done before the house is built, under the foundation / slab? Or did I read it incorrectly? Either way, I had to really push on my contractor just to do a heat pump. (And there are two large areas of sand under my house, one under my garage and the other under my sunroom.) I don't know how I could get someone to build that where I live.
I also couldn't tell if this is something that warms up throughout the year, or if this is something that warms up during the day and cools at night? Where I live, the days are very short in December / January, so I'm not sure if would work if it's day-to-day instead of seasonal.
Well, this has already happened; living in a third-world American country, I've been heating my houses in winter with heat pumps every winter for many years (even though they iced up occasionally) and most air conditioners here are already heat pumps. Frio/calor, they're called.
But, installations strictly for heating are probably never going to happen en masse. In https://news.ycombinator.com/item?id=45698730 I analyze the costs. It turns out that heat pumps cost around 39¢ per peak watt they save, while low-cost solar panels cost 6.5¢ per peak watt they produce, so it's almost always cheaper to install enough solar panels to heat your house resistively. And that gap is going to continue widening for the foreseeable future.
Our heat pump, a cheap-shit Electrolux mini split assembled in Tierra del Fuego, broke down last winter; somehow the refrigerant escaped. The repairman did a pressure test with nitrogen but couldn't find a link. He pre-emptively soldered shut a pipe that had been crimped shut at the factory, and pointed out that, probably, if we hadn't been using it as a heat pump, it would have been fine. Certainly it would have had many fewer hours of operation. We ended up spending about US$100 on the repair, which is the price of 1500 peak watts of solar panels. I think that brings us to about US$500 total spent on the thing—insignificant to people in the US, but a significant chunk of change in most of the rest of America.
Heat pumps are an energy-crisis-era efficiency measure to conserve energy. But energy is no longer scarce. After 50 years, the energy crisis is, if not ended, at least ending. If your house's solar panels are producing more energy than you can use or sell back to the grid at a decent price, the energy to run a resistive heater is free.