Even freezing air holds heat. A heat pump's refrigerant boils far below 0 °C, so it can absorb outdoor heat, compress it to raise the temperature, and release it inside. Modern cold-climate units keep 250–300% efficiency at −15 °C.

Usually yes, if your electricity-to-gas price ratio is under about 3.5. The math hinges on three numbers: your boiler's remaining life, local energy prices, and available rebates. Start with the rebates — in many regions they cover 30–40% of the install, which shortens payback to 6–8 years.