An undercover investigation by Which? magazine found that 10 out of 14 UK solar panel installation companies surveyed overstated the effectiveness of the systems.
Some companies quoted savings of as much as 50%. One company claimed the test homeowner would save £35,000 over 20 years, which the magazine described as a "massive exaggeration" - with £5,000 being nearer the mark.
Not a single company in the survey identified all the important technical challenges related to providing a quote. Only one, Southern Solar, was adjudged to have provided sensible advice.