Those gas heaters are usually overdimensioned by a few factors. Nobody needs to fill instantly fill a bathtubs with 60 degrees. My house came with an 14kW gas u

Those gas heaters are usually overdimensioned by a few factors. Nobody needs to fill instantly fill a bathtubs with 60 degrees. My house came with an 14kW gas unit, but a 5kW heatpump is enough for cold winters. Naturally the unit will be running for longer, but that's an efficiency in itself (lower delta T). Assuming a conservative COP of 4, that comes down to 1.25kW primary electricity consumption. It's a no brainer.