This post is in response to a thoughtful comment on yesterday's post.
We installed an A-rated boiler 2 years ago and have also put in cavity wall and roof insulation. Our gas bill is just under half what it was before we did this, even with the price rises.
We've also got a back porch of a kind and there isn't space for a front porch. Given that our house is more or less as efficient as it can be we are considering installing solar panels on our roof.
We wouldn't normally have money burning a hole in our pocket - who does? But we've been given some following a bereavement and it's something we've been thinking about for a while.
First the cons: well this is about the other things we could have done with the money - even given we have made our house as energy efficient as possible from an environmental point of view we could invest in a green project, pay for the woodland trust to plant trees, pay for other people to have insulation.
From a financial point of view we could put the money in a building society, invest in shares, or offshore wind.
Well the pros: it obviously generates, some, electricity/heat in a more environmentally friendly way than the beauteous Didcot power station. It also stimulates the market and hopefully encourages investment to lower costs for the future, it will be great to educate our daughter about science and the environment with, and with the feed in tariff it seems a relatively good investment that is relatively low risk (your mileage may vary, do not take investment advice from blogs!).
Of course not everyone is convinced by whether feed in tariffs are a good idea. There is a lot to be said for and against them from a policy point of view. In my view the biggest argument for them is that they will encourage market entry and thus bring costs down in the medium term, the biggest argument against is that it might be more cost effective to just insulate every house in the country. For an individual though all this is irrelevant to making a decision.
Over all the only thing that I can think of that would be both a financially sound use of the money and also have similar green 'credentials' is investing in a green company like ecotricity or similar. However I'm not sure it is as low risk because of the madness of the stock market and it doesn't have the emotional resonance. So if the numbers stack up and are comparable or better to other uses I think we will go for it.
It's nice to think I am a rational creature and play with spreadsheets and ROIs and payback periods and opportunity costs but lets face it, most of the time most of us do things because we want to...
...still lets see what the cost is first!
UPDATE: worth reading the comments as John is a heating engineer and knows his stuff!