2 ms·

> Maybe it's really inefficient cooling down the contents from room temperature while being really efficient maintaining the cool temp? After all, the latter is

> Maybe it's really inefficient cooling down the contents from room temperature while being really efficient maintaining the cool temp? After all, the latter is its main purpose.. Normal power consumption of it (assuming 18C room temperature) is less than 0.4 kWh/day. That amounts to 4.8 kWh in a 12 day period. Cooling it down from 18C takes 5.6 kWh (measured). Temperature varies of course, and the lower the temperature the lower the power consumption, and the heat pump keeps a minimum temperature of 12C. During long summer days, the indoor temperature can easily reach 26C, which will require more power, and i have not measured every possible scenario. I'm not ruling out that actually cooling down the thing during winter will require less energy than keeping it running, but i'm fairly certain that doing the same from 26C will require more power than keeping it running.

mlyle 4y ago
> Cooling it down from 18C takes 5.6 kWh This seems like a lot. It's 20 megajoules, so even at a COP of 1, it's enough energy to cool down 20 megajoules / (4182 J/kg/K) / 18 K = 265 kilos of water by 18 kelvin. And a refrigerator is supposed to attain a COP better than 1, and I suspect you have less thermal mass around than 265 kilos of water. Something is wrong-- either in measurement, or heat exchangers very badly occluded by dust, etc, or some other fault.
- 8fingerlouie 4y ago
  It does sound like a lot, and I’ve only measured once. The fridge is in a cabinet, enclosed on 3 sides, so maybe it’s not letting enough hot air out ? I could be wrong, but I think it was stated as using 184 kWh / year (at room temp 22C, optimal conditions), which is just over 0.5 kWh/day, and considering that the summerhouse is usually cooler than that (12-16C) when unoccupied, I would assume it used even less power. As it is, for this entire week, the heat pump has (self) reported using 1.8 kWh/day, and according to my power company, my daily consumption has been 1.8 kWh/day. Considering that there are 5-7 IoT things plugged in, the fridge probably isn’t using much power.
  - mlyle 4y ago
    > The fridge is in a cabinet, enclosed on 3 sides, so maybe it’s not letting enough hot air out ? Seems likely. Once it succeeds in warming its cabinet, a big share of that heat leaks back into the fridge. (And efficiency falls because of the bigger temperature difference).

mlyle 4y ago

> Cooling it down from 18C takes 5.6 kWh This seems like a lot. It's 20 megajoules, so even at a COP of 1, it's enough energy to cool down 20 megajoules / (4182 J/kg/K) / 18 K = 265 kilos of water by 18 kelvin. And a refrigerator is supposed to attain a COP better than 1, and I suspect you have less thermal mass around than 265 kilos of water. Something is wrong-- either in measurement, or heat exchangers very badly occluded by dust, etc, or some other fault.

8fingerlouie 4y ago
It does sound like a lot, and I’ve only measured once. The fridge is in a cabinet, enclosed on 3 sides, so maybe it’s not letting enough hot air out ? I could be wrong, but I think it was stated as using 184 kWh / year (at room temp 22C, optimal conditions), which is just over 0.5 kWh/day, and considering that the summerhouse is usually cooler than that (12-16C) when unoccupied, I would assume it used even less power. As it is, for this entire week, the heat pump has (self) reported using 1.8 kWh/day, and according to my power company, my daily consumption has been 1.8 kWh/day. Considering that there are 5-7 IoT things plugged in, the fridge probably isn’t using much power.
- mlyle 4y ago
  > The fridge is in a cabinet, enclosed on 3 sides, so maybe it’s not letting enough hot air out ? Seems likely. Once it succeeds in warming its cabinet, a big share of that heat leaks back into the fridge. (And efficiency falls because of the bigger temperature difference).