this post was submitted on 21 Sep 2026
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Okay cost may be one factor, but what about them is inefficient (compared to a resisitve heater not a heatpump with compressor and everything) if the goal is heat? my understanding is that whatever power they take will be turned into heat anyways plus they move some from the outside.
@viertesauge
Using the same amount of energy input, a resistive heater will output more heat.
but any electrical device is a resistive heater, no? this one just happens to move heat aswell
Key factors reducing Peltier efficiency include:
Thermal Leakage: Heat naturally flows back through the device, counteracting the pumping effect.
High Electrical Resistance: Significant energy is wasted as internal heat rather than being used for the Peltier effect. (This is essentially production of resistive heat, bit it's not where you want it)
*Compressor-based systems can achieve COPs of 3 to 6 (300–600% efficiency) by moving large amounts of heat with minimal energy, whereas Peltier devices require horrendous amounts of current to move even small amounts of heat. This is because the thermoelectric materials (bismuth alloys) have inherently low electrical conductivity, causing efficiency to drop sharply as the temperature difference across the device increases. Leading us to the next problem...
Temperature Sensitivity: Efficiency declines rapidly as the difference between the hot and cold sides grows, making them unsuitable for large temperature differentials.
Heat Dissipation: Effective operation requires complex heat sinks to remove waste heat from the hot side, adding system complexity and loss.
Peltier plates are one of those things that always seem so cool and useful until you do the math.
I absolutely hate those tiny fridges that everyone assumes must use a tiny amount of electricity when in reality, they use more than a full size chest freezer.
Thermoelectric generators can be nice, though, in the right application. I like how they are used in the biolite stoves to drive a fan that improves combustion. It's a nice feedback loop.
thanks for the wall lol. yeah like another user and I said in my other comment the actual reason is probably marginal gains even if you can get it to work.
heat dissipation is solvable with a cpu heatsink and temperature sensitivity probably isnt that relevant in this application if all you want i to protect the greenhouse from frost for example, but thermal leaking might be a problem.
It's possible future advances in materials science (the conducting alloys and heatsinks) could increase the efficiency but those are the major barriers in my non-expert opinion.
Commercial Bi₂Te₃ modules sit around ZT ≈ 1.0–1.2 at room temperature. Active research is pushing this closer to 2, but not at practical temperatures yet. (ZT is not the same as COP but it does directly relate to it for the purposes here. Even at ZT = 2, the COP gain for a heating application is modest because the device still must reject the pumped heat plus all Joule losses on the hot side.)