4 ms·

Converting a gas water heater to electric and/or solar is one of the best bang for the buck on decarbonization too. Something that should be done before buying

Converting a gas water heater to electric and/or solar is one of the best bang for the buck on decarbonization too. Something that should be done before buying an electric car or swapping out your gas furnace for a heat pump. Though I'm terrible at following my own advice, I still have a gas water heater, just because I needed to replace my car and furnace before I needed to replace my water heater. That said, the sunk cost fallacy applies to carbon emissions just as hard as it does to dollars so I have little excuse for not replacing it except laziness (and space on the breaker panel...)

ipdashc 2y ago
Is it a fallacy though? It doesn't make sense to buy a new EV if you still have a gas car that's working fine. In the same vein, I wouldn't want to throw out my gas furnace or water heater to replace with electric, creating waste and requiring the manufacturing of a new unit
- bryanlarsen 2y ago
  That only applies if you're only going to get less than 1 year of use out of a heat pump. A heat pump has an "embodied CO2" of 1.7t, which is about the same as the annual CO2 emissions of a gas furnace.
- epistasis 2y ago
  Can you explain how it's not a fallacy? Compare your lifetime emissions of replacing a gas car with an EV now versus at the "end of life" of the gas car. Emissions will always be lower if you replace now rather than later. Imagine if everybody switched to EVs right now, en masse. Emissions over the next decade, and every subsequent decade, would be massively lower. Waiting for every gas car to reach end of life before switching is always going to be higher emissions, always. Similarly, the "waste" already happened when the gas heater was manufactured. There's no additional waste when it's decommissioned. It's a sunk cost, there's no getting that back. The only question is if you switch to lower emissions now, or you switch to lower emissions later. Now, if you bring money into it, sure, there could be a financial motivation to keep emitting higher amounts of emissions. But if you take monetary considerations out of it, it's always better to stop emitting sooner rather than later. I'd love to have some serious push back against this. The best I've ever got is "that doesn't sound right..." without any engagement with the quantitation or the ideas. Which is exactly what I would expect if it was a fallacy.
  - deleted 2y ago
    [deleted]
  - relaxing 2y ago
    I think you’re assuming when you switch to EV the ICE car disappears. But more likely it got traded to someone else who has less money, eventually making it possible for someone to own a car who otherwise wouldn’t have. So the emissions stayed the same and you added the carbon embedded in the new EV.
    - epistasis 2y ago
      What would that person have bought otherwise? Another ICE. If Person A kept the ICR there would be two people driving them instead of one ICE, one EV. I do really appreciate shifting this from the "the consumer must make the right choice" to "what choices result in overall better outcomes" but we must do the full accounting.
    - asdf333 2y ago
      not necessarily. if he bought your car and traded up from a real clunker with worse fuel efficiency the net result is likely better.
      - relaxing 2y ago
        And maybe the clunker was junked, orrrrr it was subsequently resold, or put on a ship to the global south and it’s clunkers the whole way down…
        jdlshore 2y ago
        Cars don’t last forever, and shipping junk cars from the US to the global south doesn’t make economic sense. Eventually there’s a bottom of the chain.
        relaxing 2y ago
        It does and they do. A used car is cheaper to source than a new one which means it can be sold to more consumers at higher margin. Every taxi I rode in the Bahamas was a 2nd gen Jeep Grand Cherokee with the CEL on. The bottom exists, but it’s not here.
- Retric 2y ago
  You’re incorrect, buying a new EV when you have an ICE car doesn’t actually destroy the ICE vehicle. There’s a bunch of different possibilities to consider, but if you drive more than the average person buying an EV and selling your ICE is great for the environment. If you rarely drive then keeping an old ICE car out of the hands of a frequent driver has real value etc. As to the environmental impact vs retrofitting an ICE vehicle into an EV, the grid has gotten a lot cleaner over time so many of the old assumptions around EV’s are outdated. Comparing the emissions from extracting, transporting, refining, and then burning gas vs the same with EV’s built with a cleaner grid and more electrified infrastructure now heavy favors EV’s. And these calculations just keep favoring EV’s more every year.
opwieurposiu 2y ago
If you want to DIY a solar PV water heater I made a whole website about it with instructions and a simulator to estimate what your payback period could be. https://www.pvh2o.com/ https://www.pvh2o.com/
- PaulDavisThe1st 2y ago
  Resistance heating is so 20th century. Granted, you likely cannot do a DIY air source heat pump build, but the COP is so high for such systems, that it's probably worth it to just buy it.
  - opwieurposiu 2y ago
    My mom had a Heat Pump water heater at her house and I was always having to go and fix it or clean the filter. It would start beeping loudly in the middle of the night when it wanted attention. The hot water was frequently not very hot. Hopefully the new heat pump water heaters are better. The advantage of resistance heating is simplicity and cost, with no moving parts. Solar panels are so cheap now they make it hard to justify the expense of the heat pump, assuming you have room to mount the panels.
    - PaulDavisThe1st 2y ago
      a COP of 4 can certainly justify having to install 3-4x less panels. it disappoints me (but thrills me) that improvements in PV efficiency and cost have made solar thermal hot water more or less pointless.
      - NullPrefix 2y ago
        Heat pumps have COP of 4 when reaching temperatures needed for room heating. Hot water is way hotter than that. The more the difference between outside air and heated water, the less the COP becomes. I don't expect COP of 4 at 200 fahrenheit
        2y ago
fho 2y ago
Problem being that electric water heating is a lot more expensive in e.g. Germany where gas prices are lower than electricity prices per kWh delivered. (~12 vs. 39 eurocent per kWh) So blindly converting a gas water heater to electric will roughly quadruple your water heating cost.
- ben_w 2y ago
  Only a problem when you're limiting yourself to resistive heating. Heat pumps can heat water, not just air, and are several times more efficient than resistive. I've got a heat pump, and I'm in Germany. Also, if you're in Germany, you can get a balcony PV system from half the supermarkets a few hundred euros, and those are designed to be installed DIY without needing an electrician. Limited power, sure, but way cheaper than €0.39/kWh delivered: • https://www.lidl.de/p/vale-balkonkraftwerk-ecoflow-820-w-800-w-wifi-full-black-solarmodule/p100379477 https://www.lidl.de/p/vale-balkonkraftwerk-ecoflow-820-w-800... • https://www.kaufland.de/product/502015379/?search_value=balkonkraftwerk https://www.kaufland.de/product/502015379/?search_value=balk...
  - kragen 2y ago
    Your first link seems to be 349€ for 800Wp including microinverter. German utility-scale PV has a capacity factor averaging about 12% IIRC, but presumably a balcony system will be lower because it isn't optimally angled for the sun, say 8%. Then that's about 64W, which is 560 kWh per year. 349€ over 10 years would be 35€ per year, about 0.06€/kWh. That's still about six times the cost of wholesale low-cost solar panels: https://www.solarserver.de/photovoltaik-preis-pv-modul-preisindex/ https://www.solarserver.de/photovoltaik-preis-pv-modul-preis... 64 watts is about 40–50 liters per day of hot water heated resistively, presumably closer to 150 liters per day with a heat pump. But it seems like the heat pump is only saving you the 700€ for two more such balcony systems, assuming you have the space. Moreover, you don't need a microinverter for a resistive heater.
    - ben_w 2y ago
      Oh indeed, balcony systems are small and limited — the constraints that led to them are: (1) DIY-safe, (2) useful for rented apartments (limited window or balcony fencing space, may not be allowed to fix something to an exterior wall). I'm not sure if you're allowed to just resistively dump an off-grid PV system into a resistive heating system, but I guess if you did, you could indeed save on the cost of the inverter.

ipdashc 2y ago

Is it a fallacy though? It doesn't make sense to buy a new EV if you still have a gas car that's working fine. In the same vein, I wouldn't want to throw out my gas furnace or water heater to replace with electric, creating waste and requiring the manufacturing of a new unit

bryanlarsen 2y ago
That only applies if you're only going to get less than 1 year of use out of a heat pump. A heat pump has an "embodied CO2" of 1.7t, which is about the same as the annual CO2 emissions of a gas furnace.
epistasis 2y ago
Can you explain how it's not a fallacy? Compare your lifetime emissions of replacing a gas car with an EV now versus at the "end of life" of the gas car. Emissions will always be lower if you replace now rather than later. Imagine if everybody switched to EVs right now, en masse. Emissions over the next decade, and every subsequent decade, would be massively lower. Waiting for every gas car to reach end of life before switching is always going to be higher emissions, always. Similarly, the "waste" already happened when the gas heater was manufactured. There's no additional waste when it's decommissioned. It's a sunk cost, there's no getting that back. The only question is if you switch to lower emissions now, or you switch to lower emissions later. Now, if you bring money into it, sure, there could be a financial motivation to keep emitting higher amounts of emissions. But if you take monetary considerations out of it, it's always better to stop emitting sooner rather than later. I'd love to have some serious push back against this. The best I've ever got is "that doesn't sound right..." without any engagement with the quantitation or the ideas. Which is exactly what I would expect if it was a fallacy.
- deleted 2y ago
  [deleted]
- relaxing 2y ago
  I think you’re assuming when you switch to EV the ICE car disappears. But more likely it got traded to someone else who has less money, eventually making it possible for someone to own a car who otherwise wouldn’t have. So the emissions stayed the same and you added the carbon embedded in the new EV.
  - epistasis 2y ago
    What would that person have bought otherwise? Another ICE. If Person A kept the ICR there would be two people driving them instead of one ICE, one EV. I do really appreciate shifting this from the "the consumer must make the right choice" to "what choices result in overall better outcomes" but we must do the full accounting.
  - asdf333 2y ago
    not necessarily. if he bought your car and traded up from a real clunker with worse fuel efficiency the net result is likely better.
    - relaxing 2y ago
      And maybe the clunker was junked, orrrrr it was subsequently resold, or put on a ship to the global south and it’s clunkers the whole way down…
      - jdlshore 2y ago
        Cars don’t last forever, and shipping junk cars from the US to the global south doesn’t make economic sense. Eventually there’s a bottom of the chain.
        relaxing 2y ago
        It does and they do. A used car is cheaper to source than a new one which means it can be sold to more consumers at higher margin. Every taxi I rode in the Bahamas was a 2nd gen Jeep Grand Cherokee with the CEL on. The bottom exists, but it’s not here.
Retric 2y ago
You’re incorrect, buying a new EV when you have an ICE car doesn’t actually destroy the ICE vehicle. There’s a bunch of different possibilities to consider, but if you drive more than the average person buying an EV and selling your ICE is great for the environment. If you rarely drive then keeping an old ICE car out of the hands of a frequent driver has real value etc. As to the environmental impact vs retrofitting an ICE vehicle into an EV, the grid has gotten a lot cleaner over time so many of the old assumptions around EV’s are outdated. Comparing the emissions from extracting, transporting, refining, and then burning gas vs the same with EV’s built with a cleaner grid and more electrified infrastructure now heavy favors EV’s. And these calculations just keep favoring EV’s more every year.

opwieurposiu 2y ago

If you want to DIY a solar PV water heater I made a whole website about it with instructions and a simulator to estimate what your payback period could be. https://www.pvh2o.com/ https://www.pvh2o.com/

PaulDavisThe1st 2y ago
Resistance heating is so 20th century. Granted, you likely cannot do a DIY air source heat pump build, but the COP is so high for such systems, that it's probably worth it to just buy it.
- opwieurposiu 2y ago
  My mom had a Heat Pump water heater at her house and I was always having to go and fix it or clean the filter. It would start beeping loudly in the middle of the night when it wanted attention. The hot water was frequently not very hot. Hopefully the new heat pump water heaters are better. The advantage of resistance heating is simplicity and cost, with no moving parts. Solar panels are so cheap now they make it hard to justify the expense of the heat pump, assuming you have room to mount the panels.
  - PaulDavisThe1st 2y ago
    a COP of 4 can certainly justify having to install 3-4x less panels. it disappoints me (but thrills me) that improvements in PV efficiency and cost have made solar thermal hot water more or less pointless.
    - NullPrefix 2y ago
      Heat pumps have COP of 4 when reaching temperatures needed for room heating. Hot water is way hotter than that. The more the difference between outside air and heated water, the less the COP becomes. I don't expect COP of 4 at 200 fahrenheit
      - 2y ago

fho 2y ago

Problem being that electric water heating is a lot more expensive in e.g. Germany where gas prices are lower than electricity prices per kWh delivered. (~12 vs. 39 eurocent per kWh) So blindly converting a gas water heater to electric will roughly quadruple your water heating cost.

ben_w 2y ago
Only a problem when you're limiting yourself to resistive heating. Heat pumps can heat water, not just air, and are several times more efficient than resistive. I've got a heat pump, and I'm in Germany. Also, if you're in Germany, you can get a balcony PV system from half the supermarkets a few hundred euros, and those are designed to be installed DIY without needing an electrician. Limited power, sure, but way cheaper than €0.39/kWh delivered: • https://www.lidl.de/p/vale-balkonkraftwerk-ecoflow-820-w-800-w-wifi-full-black-solarmodule/p100379477 https://www.lidl.de/p/vale-balkonkraftwerk-ecoflow-820-w-800... • https://www.kaufland.de/product/502015379/?search_value=balkonkraftwerk https://www.kaufland.de/product/502015379/?search_value=balk...
- kragen 2y ago
  Your first link seems to be 349€ for 800Wp including microinverter. German utility-scale PV has a capacity factor averaging about 12% IIRC, but presumably a balcony system will be lower because it isn't optimally angled for the sun, say 8%. Then that's about 64W, which is 560 kWh per year. 349€ over 10 years would be 35€ per year, about 0.06€/kWh. That's still about six times the cost of wholesale low-cost solar panels: https://www.solarserver.de/photovoltaik-preis-pv-modul-preisindex/ https://www.solarserver.de/photovoltaik-preis-pv-modul-preis... 64 watts is about 40–50 liters per day of hot water heated resistively, presumably closer to 150 liters per day with a heat pump. But it seems like the heat pump is only saving you the 700€ for two more such balcony systems, assuming you have the space. Moreover, you don't need a microinverter for a resistive heater.
  - ben_w 2y ago
    Oh indeed, balcony systems are small and limited — the constraints that led to them are: (1) DIY-safe, (2) useful for rented apartments (limited window or balcony fencing space, may not be allowed to fix something to an exterior wall). I'm not sure if you're allowed to just resistively dump an off-grid PV system into a resistive heating system, but I guess if you did, you could indeed save on the cost of the inverter.