Talk Morgan Forums Community The Malvern Arms Is this the most condescending customer service ev

I've had solar panels on my house (it's a medium size, detached 3 bed) for the last year and this is my calculation:

Initial capital outlay

12 solar panels (400 W nominal output, £300 per panel). £3600
3 Kw inverter (Growatt 5000) £1300
9 KWh batteries (900£ per KWh, Growatt) £7000
Installation (including scaffolding) £2000
Remote immersion heater £500

Total £14400

Over 25 years, expect to replace the invertor twice and the batteries once (and assume battery cost is halved by then)

So the 25 year outlay is 14.4 + 2*1.3 + 3.5 = say 20k.

Last year my usage was:

1.25 MWh imported from the grid.
Cost of electricity units:   £188
Standing charge for the year: £121
So the total bill was about £400 (I was on a cheap contract up to the middle of the year, but that expired).

Overall I consumed 3.7 MWh in the year (I do not have an electric or hybrid car). I generated rather more than that and exported 1.7 MWh back to the grid (at 4p a unit I think, ffs, so this generated about £80 of revenue).

So assuming I use about 4 MWh per year and assume that 75% of this is now supplied by the solar and based on my current OVO contract (
48p per day standing charge and 28p per unit) then:

My savings yearly would be (4000 * 0.75 * 28p) = £840 per year.

To recoup the 20k outlay takes 20/0.84 = 24 years - by which time the solar panels, batteries and inverter will all need replacement.

So basically I expect to just about break even.

Of course, we could make the calculation more complicated by assuming energy costs go up over the 25 years, but then we ought to also consider that the value of money also goes down during that period due to inflation - not sure how to account for this properly.

I don’t see how sub 10-year pay back periods can be achieved (that would mean having a savings of more than £2k a year which would mean I would need to be consuming 5-6 MWh a year, but that would mean a bigger solar inverter and more solar panels and more batteries, which means more capital cost - and to do that I would either need an electric car or to use electricity in place of gas for heating).

 What am I doing wrong? Did I get ripped off on the initial installation (which was a council supported scheme, with allegedly cost savings due to scale)? Do I have too few/too many batteries - or do I need to just consume more electricity per year? Do I need to buy an electric car and get a cheaper tariff?

Don't get me wrong. Solar power is (imho) great and necessary.

Don't forget to improve the thermal efficiency of your property otherwise no matter what method of energy generation you use, it all goes out the window, floors. roof etc. Just by putting an insulation material between my floor joists I saving about 6000 therms of gas a year, I've taken a room at a time, usually when redecorating the room, by just lifting the sections of floorboards and laying down an efficient insulation material leaving a circulation gap has reduced our gas heating consumption quite dramatically to maintain the same room temperature. Not very expensive and almost immediate payback, for just a few hours work per room.

Our 3.6kWh array has been in 5 years & saved £3.5k. It cost £5.3 k so the payback is 7.6 yrs as a crude non DCF calculation. It includes an Immersun switch to heat water.

It faces due south & has generated 20.5MWh.
The FIT & export payments make up £1.48k the rest I measure as the non exported (i.e. used in house power) x the relevant cost to buy off Shell.

The 4.2kWh batteries & inverter went in later in Nov 2022. They cost £2.95k as they were ordered pre covid so by the time they arrived they were cheap. They have discharged 1529 kWh. Based upon the cost of a unit from Shell Energy at the time of discharge they have saved me £494.
So the payback is 6 years. Have more battery capacity wouldn't help as the savigs aren't there & I feel this is optimised for us given the UK weather.

I agree both don't take into account the sudden jump in interest I could be earning on the capital because of higher rates or the need to replace inverters at some stage.

It is also for now though untaxed income unlike a bank acount. As evn retired I pay tax this is good news plus it makes me feel good to save the planet

I hope that helps.

I just did a meter reading for Shell. I dont trust smart meters given the press on them. In 2022 we consumed from the grid 2370 kWh. In 2023 we consumed 1049kWh so the impact is clear not just on the app linked to the inverters but also on the official meter.

SCX358G, many thanks for creating such a detailed report on your electrical installation, all of which I found very interesting. There is little to no chance of payback for me, and it seems unlikely this house will be passed on to any family members... I do like the idea of solar as I have a reasonable area of south facing roofing, more than enough room and access for all the hardware, between the house and garage. I think Tesla may provide a variety of packages that can also be tied into their cars charging, though I do not know whether the car`s battery can/could be used as backup to supply the house in times of power outage, could be handy if living in remote locations where power outage can be an issue, as it once was for me..

I would suggest that unless there is some sort of designed-in obsolescence, that an inverter should last forever, and that such is the search for ever improved battery performance that it seems Tesla expect their car battery`s to last for a decade, and given the charge discharge and loading they may experience, I suspect household loadings could provide battery`s with a much less stressful life thus extending their serviceability considerably..?

Of course it is natural that from the largest businesses to one band contractors are out to make a profit, at least on the installation side of things there are regulations providing..err..guidelines but..?? Luck will ever play it`s part..?

Governments should be involved in ensuring manufacturing industry design is such that designed-in obsolescence as a process is outlawed, especially in the solar energy and other green related processes, given there will be a huge demand for decades to go green, thus more than enough business generated to provide reasonable profits well into the future...

JohnH, could not agree more re the benefits of insulation. I through a process of self building doubled the size of my 50`s brick built house. Such were the building regs at the time that wood frame with an outer skin of blockwork was the way to go, and of course insulation had to fill the voids in the framing of external walls... I took that further and insulated between each of the rooms, in that I also fitted underfloor heating, the pipes of which were mounted onto a bed of insulation all of which was covered with a self levelling screed on which either tile or wood was used as floor covering... each of the rooms has it`s own thermostat controlling valves on a manifold... I expected the costs of energy consumption of the now enlarged home to increase considerably, more so in that I had added a sun room with seven large windows...though when the cost was much less than I imagined, I set to insulating the original part of the house using dot and dab process to mount insulation backed plaster plates to insulate all the internal walls that had external facing elements, and upped the thickness of the loft insulation to match that in the new build... As I was re-tiling the roof, I also built-in attic space ventilation by way of tile vents and a vented ridge to hopefully avoid condensation and rotting timbers etc.

Yeah a great pity that a few years back the government seemed to suggest that grants to help the populace to insulate their homes was perhaps just green cr*p...?

Do those figures also include installation costs, John? Or did you install it yourself?

Many thanks

That was installed by Greenscape Energy. Suffolk Costal Council ran a bid campaign where they negotiated for all the residents who asked for a quote. I know costs went up post covid & with the rising power costs.

Many thanks, Yes, my council ran a similar thing under the Solar Together scheme, using Infinity Renewables as the installer. I've no issues with the quality of the installation, but I could never get a plausible demonstration that this was lower cost than anybody else doing it. In the end though maybe the planet will melt a smidgeon more slowly than it would have done.....

I came across this inflation calculator which might come in handy for some...?

https://www.bankofengland.co.uk/monetary-policy/inflation/inflation-calculator

Yes it was the solar together scheme. I did for the batteries look around and they were a fair price. Tesla was 3 times the price but with off grid capability and a longer life. My man mates were ok at the lower price. When I bought them I paid 16p per unit not 28 so the payback was pretty long. Energy price rises have come in to help.