A number of neighbours have gone over to Solar for hot water using the vacuum collector system and it seems a very good idea, however the cost of significant (circa £3K) and requires a fair bit of specialised plumbing, for example a new tank with 2 coils.
I wondered about the cost/benefit of using solar electricity to heat water.Sounds crazy but my tank already has a top-up immersion heater and I wondred if this could be run from batteries. Looking on ebay I noticed that there are 12/24v heaters than can produce 500 watts and can replace an existing immersion heater .
I know that the specific heat capacity of water is very high so heating a water tank would require a lot of fully charges batteries and hence panels to charge them. However every degree you can heat the tank for free is one that does'nt need gas right ?
Electric also has some advantages. It might be possbile to do this in an incremental way thus spreading the cost i.e adding panels/batteries as you can afford them.It could also incoporate a wind charger to get some power in all light conditions i.e at night. Finally the plumbing might not need changing at all to incorporate this meaing this falls within the realm of a purely electrical installation + some mechanics to fit the panel/ wind charger
I understand that electro voltaics are pretty inefficient, but I wondered if this approach might be cheaper or even more cost effective than the full solar hot water panel system ?