Solar Tubes. Solar water heating systems = Solar panels + solar energy. Solar thermal: solar power & solar hot water. RHI.
Evacuated tubes have never been supplied by Solar Twin Ltd since they started installing solar thermal in 1999 because of several shortcomings. These include their fragility, tendency to overheat and high pump power requirements which can negate over 20% of their environmental benefits according to DTI side by side tests referred to elsewhere in this site.
Granted, these solar vacuum tubes for domestic water heating are slightly more efficient per square metre, however this is usually of little importance since, to need the (marginal) extra space-economy of evacuated tubes, solar customers would have to be living in garden sheds with roof areas of 6 sqm or less. In reality most home solar thermal installations are smaller than this in area.
One leading UK government-preferred brand under the Low Carbon Buildings Programme Phase 2 subsidy was suddenly withdrawn from the market because thees particular vaccy tubes started blowing up and showering the people below with bits of broken glass.