Absolutely - but the important thing is that you can actually get a 20kW gas boiler, but you can't get a consumer 20kW heat pump. You can buy the most expensive consumer heat pump you can find, and it won't do at all if you actually need 20kW. So you can as well save the money as you'll have to install a gas heater (or oil or wood heater) anyway.
> Absolutely - but the important thing is that you can actually get a 20kW gas boiler, but you can't get a consumer 20kW heat pump.
If even you could, you may not want to. Instead one external heat pump handle heads on the top floor, which is generally bedrooms, and not occupied during the day; a second external unit to handle heads on the main floor, which are generally not occupied overnight.
Each individual smaller unit runs less because the load is more focused in 'zones'.
