3 ms·

> 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.

by kragen 1y ago

> 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 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.

gwbas1c 1y ago
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.
- kragen 1y ago
  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 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!
  - gwbas1c 1y ago
    As I read https://news.ycombinator.com/item?id=45690085 https://news.ycombinator.com/item?id=45690085 : 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.
Marsymars 1y ago
> But, installations strictly for heating are probably never going to happen en masse. In https://news.ycombinator.com/item?id=45698730 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.
- kragen 1y ago
  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.
  - Marsymars 1y ago
    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.
    - kragen 1y ago
      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.

by kragen 1y ago

gwbas1c 1y ago

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.

kragen 1y ago
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 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!
- gwbas1c 1y ago
  As I read https://news.ycombinator.com/item?id=45690085 https://news.ycombinator.com/item?id=45690085 : 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.

Marsymars 1y ago

> But, installations strictly for heating are probably never going to happen en masse. In https://news.ycombinator.com/item?id=45698730 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.

kragen 1y ago
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.
- Marsymars 1y ago
  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.
  - kragen 1y ago
    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.