We've had 5kW PV, a 3.7kWh inverter + 6.7kW battery storage for quite a few years and receive reasonable FIT payments. For us, the factors determining whether a Solar installation was going to be worthwhile included:
- Electricity prices will continue to rise so even if the payback doesn't initially look good, it will improve over time (has done significantly already)
- Aspect, ideally South facing (we are SSW)
- Remaining in the same house for a long time (in our case, for the rest of our lives) edit: I hope I don't mean lockdowns
- Can you afford to spend the money even if the return may not make sense initially? (Undoubtedly our batteries will need replacing within the life of the installation & panels do gradually lose a few %. However our FIT payments will always rise by a fixed % or RPI over 25 years total). I effectively 'wrote off' the initial installed cost of the system as it was something I wanted to do but in 6 years we've already recouped 30% directly and probably more indirectly (including in a small way 'window cleaning' as I use one of those extendable fibreglass brush/water things that reaches up to and over the roof - surprising how much generation can be lost through bird muck & general grime build up on the panels if ignored).
- We always intended to get an EV and use any surplus generated. Until last year we were exporting far too much even though the FIT scheme pays out regardless of use or not & even after purchasing the Model 3 in April, we still exported a fair amount throughout the summer months.
- It's nice to be self-sufficient whenever possible and of course good for the environment (+ the batteries have seen us through a couple of local power cuts)
- With Solar I've made sure all appliances wherever possible are electric so they can either be used during the day (lawnmower, hedge trimmer, chainsaw, DIY saw bench, pillar drill etc) or on timers (EV, washing machine, tumble dryer, dishwasher, water heaters & storage, rechargeable vacuum cleaner, rechargeable power tools etc). We also switched out the gas hob/oven to Electric several years ago.
It's true that winter months generate very little solar, however on many winter days there is still sufficient to power the house throughout daylight hours, including gas central heating pumps (2 systems), kettle, lights, occasional TV etc (but rarely oven/hob). Frequently the batteries have sufficient to carry through to mid evening even in December-January and by now, February there are a few days where the batteries fill completely (two in the past week) or last through until bed time.
From March - October the PV system basically powers everything, and if battery storage runs out it's usually in the early hours. I used to be on Octopus Agile, since February on Go Faster 02.30-06.30 & may reman on that because in summer those hours are basically the only period where we would sometimes draw from the grid anyway.
We have a lot of devices powered via smart sockets and some are ready for charging whenever or as soon as the house batteries are filled. Nothing particularly 'smart' about the process itself - I receive a smart phone alert & remotely switch whatever I want from there if I happen to be out (...vaguely remember times like that).
Without FIT, payback will of course be lengthier even though Electricity suppliers do have export tariffs. FIT pays out regardless and does not directly differentiate between generation and export ('assumes' 50% export), the replacement scheme only pays against measured output itself.
