On these long clear days our 300 litre hot water tank routinely gets up to about 73 °C. Doubtless this is due in part to the fact that we are a pair of soap dodgers who don't shower three times a day like some people I won't name. Our washing machine and dishwasher only take cold feeds so on clear days there is a real problem disposing of excess hot water. It's a bit like a micro version of a data centre.

I know I could add a tree way valve and divert some of the heat to a radiator to dump the excess energy, but I'm wondering if another solution might be to generate a lot less heat in the first place. We have a four panel array of black tubes. Six tubes per panel making 24 in all, each about 1.6 m long. This seems like a very large array for a three bedroomed bungalow. Would it make sense to cut this down to two or three solar thermal panels, liberating more space for solar PV panels?