[nimbix]

If you pair a heat pump with good insulation, the effect can be quite staggering. My parents moved into a new house 6 years ago and their annual heating bill (for space and water) dropped from ~2500EUR down to around 300EUR.

This is in an area where night-time winter temperatures hover in the -5°C range, occasionally dropping to -10.

The old house was around 30 years old, with fairly thin insulation (5 or 7cm was pretty standard back when it was built), and had an oil burning furnace for heating.

[mattiasberge]

That can’t be right.

[gorkish]

From 2500/yr to 300/yr is 88% reduction in cost.

Heat pumps are 300% - 500% efficient, enough to represent a 66% to 80% savings on their own. Adding insulation reduces the total amount of heating necessary, plus heating oil and electricity aren't priced the same per-unit of energy.

This is not unbelievable in the slightest. Perhaps if you find it surprising, you should ponder where your reasoning got hung up.