Some of that heat goes up the chimney. A good quality log burner, used correctly (and I believe that most people who use log burners have no effing clue how to do so) is at best 60-80% efficient.

Plus you have to account for the energy used to grow, harvest, season & transport the wood, even before you throw 20-40% of it away when you actually burn the damn stuff!

I think GP might be referring to a gas burning boiler.

Same principle just with a different efficiency number. I doubt any but a fraction of combi boilers are 98% efficient: most people run them too hot, so they aren't able to recover sufficient energy to reach that goal. But in any case, you now have to account for installing and maintaining the gas network, refining the oil into gas, shipping the oil to the refinery, extracting the oil in the first place, exploring for the oil in the first place, and so on.

It's far more efficient to burn that fuel to move existing energy from one place (outside) to another (inside)... you can turn 1J of fuel into 4J of heating if you're lucky!

Burning fuel is pretty efficient, until you realise that heat pumps have an efficiency greater than 1. So a heat pump driven by electricity uses less energy than burning fuel in a boiler. If the electricity is renewable, so much the better.

Heat pumps, however, do not work in all climates

The range of climates that heat pumps work in has expanded a lot in recent years. Some modern heat pumps work efficiently down to -20C or lower.

I'd be surprised if there was anywhere in the UK where modern low-temperature heat pumps regularly don't work.

True, I forgot about heat pumps. That’s one of the few times physics let’s you “cheat”.

> burning fuel is as efficient as it gets

Considering this is false as many commenters have mentioned, do you feel any obligation to edit or delete your comment?

Umm, no. I stand by it, although heat pumps hasn’t occurred to me.

But a typical electric heater is probably not going to match the efficiency of a natural gas heater. It matters how much energy is lost in generation and transmission versus extraction and transmission though.

Also I don’t care for your comment. I think if we met in real life, we would not be friends.