A heat pump is much more effective if you only have a small temperature difference [0]. If your house is well insulated and you have underfloor heating, you can

A heat pump is much more effective if you only have a small temperature difference [0]. If your house is well insulated and you have underfloor heating, you can heat your house with 40°C (sorry for European units) water to keep it warm inside. If you have poor insulation and small heating elements, you need much hotter water (>60°C). A heat pump can have a carnot efficiency (theoretically achievable efficiency) of >10 to warm water from 20 to 40 degrees, but only ~5 if you have to heat it from 20 to 60 degrees (not sure about the numbers, but you get the idea). [0]: https://energyeducation.ca/encyclopedia/Carnot_efficiency https://energyeducation.ca/encyclopedia/Carnot_efficiency