It was good to see the article “What it costs” (22 September, page 81), presenting the value of photovoltaics (PV) in reducing energy costs and cutting carbon dioxide emissions.

However, I think the author missed a trick when he listed the factors that influence the costs and benefits of PV systems, because he neglected to mention the cost of electricity.

One of the inherent advantages of whole-life thinking is that future costs are factored in. Does he think that energy prices will stay the same?

The net present values in the table could be lower, that is, more favourable, if current and future electricity costs were allowed for.

Ian Butterss, Faithful + Gould