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Modern heat pumps work well below freezing, in Chicago 2021 there were 4 days that gas heating would be more efficient. Maybe don't use a radiator? American he

Modern heat pumps work well below freezing, in Chicago 2021 there were 4 days that gas heating would be more efficient. Maybe don't use a radiator? American heat pumps hear air directly.

rad_gruchalski 5y ago
> Maybe don't use a radiator? And how do you do this in a building never designed for this king of system?
cycomanic 5y ago
Heating the air is less efficient, by a significant margin (you need a high temperature for the same comfort level). Using US houses as an example is quite laughable, the energy consumptions of US households is much higher than German ones.
- hedora 5y ago
  I doubt heating air to a higher temperature with a heat pump is less efficient than natural gas heating. The heat pump will have a coefficient of performance over five for small temperature differentials. For huge differentials, the thermal loss of the building is linear in the differential, and dropping the thermostat a few degrees only drops a few percent of thermal loss. In those scenarios, the COP of the heat pump is still something like 1.5 or 2.
- scythe 5y ago
  >Using US houses as an example is quite laughable, the energy consumptions of US households is much higher than German ones. It's an extremely heterogeneous dataset, but a cursory analysis does not agree: Germany: 136 kWh/m^2 https://bpie.eu/wp-content/uploads/2018/01/iBROAD_CountryFactsheet_GERMANY-2018.pdf https://bpie.eu/wp-content/uploads/2018/01/iBROAD_CountryFac... US: 47000 Btu/ft^2 — because we like dumb units — 148 kWh/m^2 https://constructionphysics.substack.com/p/looking-at-energy-use-in-us-residential?s=r https://constructionphysics.substack.com/p/looking-at-energy... That's a slight win for Germany, but it's not by much. For the most part, US houses are simply larger than German ones, which is where that energy use comes from. (US temperatures are also harsher, in both directions.)

Modern heat pumps work well below freezing, in Chicago 2021 there were 4 days that gas heating would be more efficient. Maybe don't use a radiator? American heat pumps hear air directly.

rad_gruchalski 5y ago

> Maybe don't use a radiator? And how do you do this in a building never designed for this king of system?

cycomanic 5y ago

Heating the air is less efficient, by a significant margin (you need a high temperature for the same comfort level). Using US houses as an example is quite laughable, the energy consumptions of US households is much higher than German ones.

hedora 5y ago
I doubt heating air to a higher temperature with a heat pump is less efficient than natural gas heating. The heat pump will have a coefficient of performance over five for small temperature differentials. For huge differentials, the thermal loss of the building is linear in the differential, and dropping the thermostat a few degrees only drops a few percent of thermal loss. In those scenarios, the COP of the heat pump is still something like 1.5 or 2.
scythe 5y ago
>Using US houses as an example is quite laughable, the energy consumptions of US households is much higher than German ones. It's an extremely heterogeneous dataset, but a cursory analysis does not agree: Germany: 136 kWh/m^2 https://bpie.eu/wp-content/uploads/2018/01/iBROAD_CountryFactsheet_GERMANY-2018.pdf https://bpie.eu/wp-content/uploads/2018/01/iBROAD_CountryFac... US: 47000 Btu/ft^2 — because we like dumb units — 148 kWh/m^2 https://constructionphysics.substack.com/p/looking-at-energy-use-in-us-residential?s=r https://constructionphysics.substack.com/p/looking-at-energy... That's a slight win for Germany, but it's not by much. For the most part, US houses are simply larger than German ones, which is where that energy use comes from. (US temperatures are also harsher, in both directions.)