this post was submitted on 21 Sep 2026
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That doesnt really answer my question. my understanding is that if I have a resisitve heater that takes 100W of power and a peltier that also takes 100W of power, the peltier will actually give me 100W + whatever heat it moves from one side to the other. So if my goal is heat, then a peltier would give me more for the same amount of electricity, no?
That understanding is mostly correct, but when you crunch the numbers, the “ + whatever heat it moves from one side to the other”-component of the equation tends to be small in practice relative to the input energy, such that you wind up very close to resistive heating. At best, you’ll get a COP around 1.5.
That means you pay a lot of overhead for marginal efficiency gains, and if you have clean electricity to run your heat pump, you already have clean electricity to run resistive heat.
yeah marginal gains are probably the actual reason
I'm no expert, but from what I have been reading. It seems that it is difficult to design a heatsink that is able to dissipate the heat quickly enough before the entire device heats up and causes the cool side to warm and efficiency to drop.
i thought about using a cpu heatsink and fan. those are designed to dissipate 100+ W of heat.
You're not going to be able to heat a greenhouse in temperatures where frost is an issue with only 100w (~341btu) of energy.
that number was just an example, of course you could scale things up as needed (multiple elements with multiple heatsinks for example)
No, you’re using 100w to move 100w. You can’t ever have more efficiency than you put in.
What would you be cooling to get the heat? If it’s cold outside at night, there’s nothing go take heat from either. You would need a way to store it during the hot day.
its a heatpump, of couse I will have more Watts in heat on one side than i put in as electricity
This is not correct.
Heat pumps are capable of being more than "100% efficient" because they are tapping into an external heat source, the electricity that is being used to operate the device is not the entire sum of the energy available to the device.
Once you step out to the greater picture of the electricity + the available environmental energy, then it returns to equilibrium, but when you're only calculating wattage and the electricity required to operate it, then you can get up to four times the amount of heat output per watt of electricity used with a properly designed system compared to a resistive element.