You don't say which kind of solar. PV I wouldn't know. But low savings from solar thermal is very believable. When 'Which' came out with their own research in 2010 - ie £75 PA typical saving from solar hot water (not including any grants under the RHI), not many in the solar industry wanted to believe it.

Mis-sold tony? Mostly are IMO. Why? Because at present approved training courses teach plumbers only to produce these feeble savings, when we could do so much better. Ask several members of this forum who have their oversize arrays tapped into thermal stores.

Do you have a link to the report in question please?

If my SAP worksheet is anything to go buy windows are certainly a big offender....60m2 of glazing with a U of 1.8 Wmk loses more heat than 400m2 of wall (0.19) and roof (0.1)!

I'm in the process of having the SAP re-done to consider better windows...not sure if the cost/benefit will justify windows better than 1.4-1.5 as an average?

You can juggle the figures around to show pretty much anything, depending on the newsworthy slant or political bias you want to impart to the report.

Using cost effectiveness of energy saving measures as a baseline puts windows fairly well down the list, simply because any replacement windows, good or bad, will be a high capital cost item.

Using total household energy loss as the baseline moves good double, or triple, glazed windows well up the list, simply because they are a major source of heat loss for most homes.

We're fond of always trying to look at energy saving in terms of return on capital investment, whereas I believe we should start from a position of always looking to minimise energy wastage, and use that as the yardstick for comparison.

I fully accept that refurbishment of existing housing stock is going to need greater compromise when it comes to reducing energy loss, than, for example a new build. Windows are a good case. The incremental additional cost of fitting super-insulated 3G windows over bog standard 2G in a new build is modest, with a shorter pay-back time from the initial investment than that from replacing serviceable existing windows in old housing stock. It doesn't alter the fact that poor windows are a major source of heat loss and wasted energy, though, and that, after all, is the most significant issue for the future.