[aoner]

Just use an air to water heat pump. We've got one installed in the netherlands, costs was about €6k (ex subsidies) and we're disconnected from the gas supply. The newest generations can go up to -25 degrees celcius (look up Mitsubishi zubadan for example)

[jessaustin]

You shouldn't assume that your climate is the same as the one GP referenced.

[aoner]

Air to water heat pumps are also used in harser climates. If you're interested here is an example datasheet of an air to water heat pump (2018) (using Celsius here):

PUHZ-SHW112YAA Guaranteed operating range (outdoor): Heating: -28 to +21 Domestic hot water: -28 to +35

On page 108 you can find the actual co-efficient of performance (COP) for different outside temperatures and inside water heating temperatures. As an example: at -10 and an water temperature for heating at 25 you still get a COP of 3+ (which are the average low temperatures in Maine). That means that 100% electricity moves 300% of heat into your house.

[arcticbull]

The climate is harsher than -25C/-15F in the winter?

[jessaustin]

GP cited Netherlands. No way that's a typical temperature.