Your latitude is 34 North ... the whole of UK is above the 49th parallel so different ball of chalk here, in the payback sense.
solar panels at home? Are they a fad?
Definitely not a fad ... prime agricultural land around here is smothered in them, probably on 30 year contract, certainly 20 year
So farmers must be making more money sat in armchairs than driving a Tractor and Combine around the fields growing Wheat ...
The Feed In Tariff government handout has gone (for new installs) and there is talk (maybe its actually policy by now?) of removing the 5% VAT rate in the Autumn - so if you are going to do it don't delay.
But this usually comes down to doing something for the planet, not your pocket. If you are in your house for a long time then payback is probably OK, particularly if you attach a value to the fringe benefits (e.g no power cuts)
Price of PV panels came down significantly last Autumn (change to import duty I think ...) so although FIT has gone panels are cheaper - so Payback-Maths may well be about-the-same.
You still get paid for Export to the Grid, but its not-a-lot. That used to work by self-declaration - you read the PV Meter [how much you have generated] and you get 50% of that as your "Assumed export" (but now you might have to install an Export Meter
). if you are out to work Mon-Fri then presumably the only thing on in your house is Fridge/Freezer, and you will exporting 99% and getting paid 50%
... you can get devices that will turn on your immersion when you are generating more than you are using, so then you export 0% but still get paid 50% export assumption
If you are working from home, able to charge your car at home during the day (Zappi wall-charger can charge your car only when excess solar PV available) then you can probably use 100% of what you generate, by one means or the other.
Insolation ("
Power of the sun falling on e.g. your roof") is 90% less in mid winter (at UK latitude), so you will get the best part of f-all in Winter. So forget about using PV to supplement winter heating (whereas if you were in USA latitude that would be a no-brainer)
Regs vary, but in essence you can export what 16 panels will generate. If you have more than 16 panels then a) maybe they will let you export more (infrastructure near you can "shift" the excess, so a cement works next door might be a reason
), OR you limit what you export (pointless unless you can "use" the remainder ... or store in a static-storage-battery / car)
if you have a Battery THEN you might decide to put in loads-of-panels - if your roof is big enough. Then your aim would be to generate 100% of your Summer usage, perhaps excluding the Car (UNLESS you ARE home during the weekday) [it makes little sense to go PV->PowerWall->HouseWiring->CarBattery ... there are losses all along the way ... but that would be fine to use up occasional over-generation, or for extra-Green-back-patting
)
NOTE: All my money-numbers are off-top-of-head guess
Battery is £5K plus £2.5-3K install. I don't know if one is enough to run your house, if you have a large house or loads of power-hungry stuff (Servers, always-on home entertainment ) then "no". I think install cost s about the same for 2x powerwalls as 1x ... and if you install PV at same time as PowerWall(s) you get the 5% on all them too (my guy will install you a very tiny PV panel if you want a power wall installed ... my guess is Your Guy would too
)
PV on the roof, with scaffolding, my guess £10K. (You can ground-mount if you have space / field / etc.)
Payback:
So you now have, lets assume, 75% reduction in electricity bills - 100% in Summer, not much in Winter. You now buy (and store) whatever electricity you DO use at the cheapest rate - so you can have Octopus Go, or whatever, with a 5p unit cost between midnight-and-4AM (crucial to avoid using any electricity at their Peak rate, which is "evening when cooking", so you need battery to achieve that). So you are saving 10-15p a unit when you DO buy Juice from the grid.
So assume you generate (and save) 75% of you annual electricity bill, and for the remaining 25% you get that at, say, 50% discount. How much is that? (Big house / big user works better here
)
You have paid £10K + (£5K + £2.5K) for the Gear
You are saving £X per annum
Could you get that return on your money with your current investments? if not then JFDI
(If you would have to borrow the money then forget the whole thing)
Side benefit: The Battery will run the house during a power cut. It is not (AFAIK) guaranteed to switch over fast enough to prevent a computer rebooting (i.e it is not a UPS, or at least "not yet, in UK" although I think it can be in USA), but in practice it does switch over fast enough - i.e. before power-supply capacitors in Computers lose their charge.
P.S. South facing roof best, but West is almost as good (generating peak later in the day, which will coincide with when you come home in Summer), and you can also do a combination East-West which will give you peak from East in the morning and West in the afternoon, so overall a lower spike than South facing. But with battery it is moot, you'll store any excess however generated, and in that case South is (marginally) better.
If you have trees that cast a shadow on the roof then forget it.
