Comment by icehawk

Comment by icehawk 2 months ago

11 replies

> So cooling a living space is always more costly than heating a living space. Simply because all the waste energy created by people living in the space reduces the total heating requirement of the space, but equally increases the cooling requirement of that same space.

This simply is not true for a furnace or electric resistive heat.

My furnace produces 0.9W of heat for every 1W of energy input. More efficient ones do 0.98, the best you get with electric resistive heat is 1W.

On the other hand my air conditioner moves 3.5W of heat outside for every 1W of energy input.

avianlyric 2 months ago

There’s a reason I say living space, I.e. a space with people living in it.

A living space will naturally heat itself with zero furnaces or electric heaters. Because the living things inside it will always produce heat (at least until they cease to be living). On the other hand, you’ll have a hard time getting living things to cool any space they occupy.

> On the other hand my air conditioner moves 3.5W of heat outside for every 1W of energy input.

Heat pumps work both ways, and it’s still easier to heat a space with a heat pump than cool it. Sure your AC can move 3.5W of heat for 1W of energy input. But that means 1W of energy allows you to remove 3.5W of heat from a space. But if you used the heat pump to heat the space, you would get 4.5W of additional heat, because that 1W of energy used to power the heat pump becomes waste heat that can be trivially captured and used to heat the space.

EVa5I7bHFq9mnYK 2 months ago

My AC works in both directions, in winter it moves more cold outside than the power it consumes. Not sure what the factor is exactly, but I think same as for cooling.

  • datadrivenangel 2 months ago

    Thermodynamics unfortunately disagree. As your temperature deltas get smaller efficiency goes down.

    • EVa5I7bHFq9mnYK 2 months ago

      "Thermodynamics" is singular :) As for the numbers, my AC's manual shows COP of 3.71 for heating and 3.13 for cooling.

      So you are spot on, in winter temperature deltas are larger, and efficiency goes up.

tshaddox 2 months ago

> My furnace produces 0.9W of heat for every 1W of energy input.

I assume you mean that 10% of the energy immediately escapes your house?

  • icehawk 2 months ago

    Yes, last 10% goes up the chimney, so only 0.9W goes into the house.