We are often asked about the pay-back time of the energy saving improvements we've made and the gadgets we've bought. Our standard answer has been that it's too difficult to calculate and, anyway, not a factor in our decision to do it. But we've finally given in to pressure and have attempted to come up with some figures.

The exercise has convinced us that it is well nigh impossible to give a meaningful answer.  Even estimates of annual savings brought about by any particular change are very crude and can't be used to predict savings from similar investment by others:

But, if you are really keen on figures about the value of this kind of investment, take a look at the following:


Detailed calculations - spreadsheet

Simplifed version -   pdf file



Payback time