I had an evacuated tube hot water system in Tas and marvelled at the efficiency but it did have a couple of drawbacks. The installation from the panel was in flexible plastic tubing, not copper and the system depends on that pump circulating the water through the main hot water storage tank in cycles as the temperature parameters are reached. Problem is, with a power cut or pump failure, the water will quickly get hot enough to blow the plastic tubing. I was slow to fit copper pipes and when the sun came out during a power cut I actually got on the roof and covered the tubes in a tarp. Of course as soon as walked in the house the poxy power came straight back on so I had to get back and take it off, in a howling gale.
Are you aware you can get a cheap reflector to fit on the back of the tubes that dramatically increases the efficiency? You might already have one!
In defence of the old systems, a friend had one fitted to their new house and got 28 years without touching it and it was still going good when they sold the house recently.
