After have a little dabble with a couple of solar panels and battery I've come to realise you can generate a lot of free electricity for not too much outlay in panels. (£60 for 400w panel)
I can see how it completely makes sense to have a couple of small bitcoin miners for some winter heating to spend some of that excess solar power.  

 How much electricity does 1 mining rig use per month?  You need a large system to get a lot of electricity 

 I'm only thinking something very small that would work well with panels. The new heatbit mini interests me as it only uses around 400w