One option you have is what we have - an air to water heat pump. These will go on the outside of your house.
How they work is like an air conditioner in reverse. They take the heat out of the air outside your home. These units have a COP (coefficient of performance). This is how efficient the heat pumps are. Heat pumps are cheaper to run then purely electrical boilers. this is because while a purely electrical system will be around 99% efficient, a heat pump could be 300% efficient. How? the heat pump doesn’t make its own heat energy, rather, it just moves the heat from outside, to inside. There are some downsides compared to a gas boiler though, for example, radiators will not get as hot as one from a gas boiler, so your home takes a little longer to warm up. this could also mean you need larger radiators.
For residential property, I would recommend an ‘ecodan’ heat pump. these can heat a hot water tank, and a central heating system.
Hope this helps.