Peter and Tim, I am curious as to what is the payback period for your installations and are there maintenance costs that have to be included in that costing e.g. new batteries, panels, etc? I realise the costs can be somewhat subjective dependent on the system/consumption, we have over 300 days of sun a year and are South facing so an ideal candidate but would have to convert the house from gas to electricity which is quite a cost to add.
I have no FiT contract or Smart Export Guarantee scheme (its successor) payments, so the payback calculation for our system is not brilliant.
We paid a smidgeon over £33k for 2 installations giving a total maximum output of 9.6KW and 14KWh of storage capacity, with an estimated generation of around 9000KWh/year. There's a 25 year guarantee on the panels and 12 years on the battery (including labour) with free remote management and software upgrades.
If we use all the generated power ourselves a projection based on £0.20/KWh rising at 2%/year (average UK inflation) then we end up with a 15 year payback - but of course we won't be able to do that, in the summer we'll have far more power than we use. If we cut the usable output down to half, ie 4500KWh/year then it's a fairly nonsensical 25 year payback.
BUT (and it's a big but) - the energy inflation rate is much higher than the average, it's been 5% for the last 5 years, and I have no confidence it's going to fall any time soon. So plug in a 5% inflation rate into the calculation and you get a payback of 20 years - which is a bit more palatable. If the UK messes up its energy strategy (quite likely) then I wouldn't be surprised if we get higher inflation figures as we run out of generation capacity (nukes going offline and nobody building replacements).
Either way as I said it's not brilliant, but what the hell, we aren't doing it for the money.
