The Natural Philosopher wrote:

pete wrote:

Agree about the insulation, though it turns out that the DG is a loss maker.
The cost of heat-loss through SG windows[1] doesn't even pay the interest
on the cost of having it installed. DG cost: £5200, interest @ 5% = £260 p.a.


MOST savings on DG come from replacing leaky, rotten and draughty
windows with ones that seal properly.

Not from the actual DG itself!

Oh, I'd agree with that. The reason the original SG units were
replaced is because the house-builder forgot to seal the bottom
frames, and they all rotted.

Installing the DG evened out the temperature gradient across the
lounge, which coupled with the reduction in draughts really raised the
comfort level.

[1] Heating fuel savings (est. 20% of _heating_) = ~ £50 p.a.