[petercooper]

I have the means and the property (albeit small) to do this but.. no chance. The main payback (ignoring the environmentalism externality) is dependent upon a government subsidy rather than actual savings or efficiency gains and as soon as it suits them, the government can yank the benefit away and you're sat with an expensive piece of plastic on your roof that'll take 20 or more years to pay for itself. (I seem to recall the government encouraging the use of diesel in the 80s and LPG in the 00s through reduced duties, yet both are now in the same sky high ballpark as petrol once their respective efficiencies are taken into account.)

[dangravell]

Is that true for these particular subsidies? Or has the UK government committed to them over the coming 15-20 years? I thought the latter.

[petercooper]

Hopefully someone who knows for sure will comment, as I didn't know that. Even if they did, though, I'm not sure I trust the government to stick to a long-term promise because I'm not even convinced the state pension will still exist when I reach my 70s ;-)