Comment on Heat-pump water heaters are a winner for the climate — and your wallet

• orrk@lemmy.world ⁨9⁩ ⁨months⁩ ago

  ya no, I think you might be the one overlooking something here, you talk about efficiency, but leave out the energy needed to heat the water to “hot Water” in the first place, all you did was split the work, and ignore everything leading up to the second work step.

  you are getting water from the tap, let’s say 10°C and need it heated to 70°C, it will always require the same amount of energy input (10°C->40°C->70°C is the same amount of energy as 10°C->70°c), but if you centrally heat part of it you will lose energy while you store it, and during transport.

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  • Squizzy@lemmy.world ⁨9⁩ ⁨months⁩ ago

    My air to water heater operates at 4.3:1 efficiency and heats to 60°. It stores it and loses 1° a day. The dishwasher would need to heat the water just 10° more given the tank is in daily usage.

    Otherwise the dishwasher would have to do it on in a faster timeframe. This is why electric power showers are more expensive to run than mains showers, they have to heat quicker which takes more energy.

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    • orrk@lemmy.world ⁨9⁩ ⁨months⁩ ago

      fundamentally, water takes the same amount of energy to heat up, no mater the time frame, most commonly the “mains showers” are cheaper to heat because many run on some combustible

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      • Squizzy@lemmy.world ⁨9⁩ ⁨months⁩ ago

        Yes but we are not heating water with 100% efficiency. So it’s not the same, it is cheaper and more energy efficient for me to use my air to water heater to heat water and store it than it is to burn coal to generate electricity to heat an element to bring water to the same temperature

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• Mr_Blott@lemmy.world ⁨9⁩ ⁨months⁩ ago

  You misunderstand on-demand hot water

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