Here in this side of world energy costs was REAL roller-coaster
Pellets from 150 €/T went to 450 €/T. Electricity (for industrial customers) from 0,04 to o,5 €/kWh
LPG I even dont want to know. But to keep warm average house it used to be like 100 - 150 €/m for gas, now people are paying near 1k €
I have wood gasification furnace (or boiler ? I am a bit confused about terms you use).
It has 20 kW power and is connected to 2000 liters big heat accumulator. Every second day I am filling boiler with ~ 30 kg of wood and fire it up. wood burns like 5 - 6 hours, warms up accumulator from 30 C to 80 C. We have underfloor heating, so to go down till 30 is ok
/ Little break for ranting - SI system makes much more sense - 1 W is needed to warm 1 liter of water for 1 C /
Keeping that in mind we can figure out that my accu contains ~ 100 kWh of energy. That's enough for 48 hours. At least it was so till this fall
This year I have made extension for house and obviously now house needs more energy.
And parallel to wood boiler we have installed air - water heat pump
It is efficient is it has to go till 35 C max, which is ok for me. And if temperatures are negative, then as well efficiency is falling. I have used heat pump till + 5 and I have noticed ~ 3,5 COP, which is less than promised but still rather nice