Solar business case

We had a system installed just before Xmas. At the current price of electricity, payback was still nearly 20 years.

We did it more out of principle than anything else - plus I can run aircon all summer for free.....

Edit: If we'd skipped the battery (which was a big chunk of the cost), that would improve the payback period, but still >10 years.

That sounds similar. Is that with energy prices flat or inflating. If there’s no energy price inflation then I don’t think my quote will pay back, not if mortgage interest rates stay >5%. Albeit perhaps one is unlikely without the other. So many variables can sink or swim the proposal very easily.

Were looking 13k for 6kw of panels and 4.8kwh battery. Feels high but lowest quote we’ve had.

prices have inflated massively since energy costs started climbing - due to demand i guess. - i've watched equivalent material costs for panels go up 100% since i installed 2 years ago . (i have 12 panels and want another 10....) - brackets and rails also have increased /hard to find if you want specific renusols - so much so suppliers wont sell you unless either A your an installer or B- buying a complete package from them.

Equally between me ordering my battery and receiving it - the cost went from 2400 - 3600 per unit...... thankfully my contract protected me to the agreed price.

at those costs you'd need your head looking at if it was a financial decision.

That would make my equivalent install over 20 grand today......

The good news i guess is that china have said they have a glut of material required for manufacture of solar panels and prices will likely come down over the coming year.

Same for us, payback was nearly 15yrs at current energy prices. Couldn't justify the outlet £16k just now but would have liked to.

Ive just gone for it. Based on my 6kw usage i think it will take 6-7 years to payback the 9k installation cost. A battery is a must however.

only issue is the installation is a lot more shaded than i originally envisaged so this may change. I wont know till march.

Has it every really paid back the cost of install?

To me you either do it for environmental reasons, or more commonly it seems to be done by the wealthy retired who've run out of other things to spend money on! 🙂

And you've also got to spend at least 10yrs in the same house to see any return. And I presume there's maintenance costs during that period also.

It depends on many things. We had a PV and battery installed 2 months ago. There where a number of reasons why we did so now and rising energy costs was one of them, plus a desire to reduce our carbon footprint and reduce our dependence on Gas. We are helped by having a large S/W facing rear roof.
I expect the payback to be between 6 and 7 years which is quite short and I did a lot of number crunching to come to that conclusion. My experience over the last 8 weeks has not changed that but I have come to realise that how we achieve that is quite unique to us and to benefit fully from both the solar and battery requires regular “manual” input. I don’t find this onerous and much can be done via the software but using PV energy as it appears and avoiding it going back to the grid (to receive a paltry payment) makes quite a lot of difference. As does your electricity tariff.
We don’t have an EV yet but and at the moment we charge our battery fully overnight on Eco7. This takes a hit from 7:30 onwards with morning activity using up to around 15% of our battery storage until the sun (maybe) comes up around 9:30 for us and on a typical day starts to replenish the battery. Once the battery is full any excess is routed to an iBoost which heats our water. Once hot this excess then goes to the grid and our tarif provides 15p per kW, our Eco7 cost is 17p per kW so we are almost receiving what we pay. If I am around and I notice this then I tend to, for example, do an extra wash if needed or dry some washing in the tumble drier. If I had an EV then this could be routed to charge that and as our car is on the drive most of the time and our monthly mileage is quite low then we could benefit from the odd kW during the day, interestingly if we did get this then cumulatively, I estimate we could almost run an EV given it is driven quite intermittently.
So far I am surprised and am looking forward to the spring when our 5.6kW array should provide enough power to maybe even be electric cost neutral (or even positive) until around late September. I think an EV is a no brainer for us in the coming months.
The only issue we have at the moment is that with the short days we are dependent on battery power from around 3:30 onwards and like most homes we cook an evening meal using an electric hob/oven and this kills the battery. On a good day we have enough power to take us through to 12:30 when the Eco7 kicks in but if we do draw power from the grid then that is at 44p per kW. As the days lengthen this will be less of an issue.

Which part of current policy or the current government makes you think that energy prices will decrease meaningfully long term?medium term.

Equally why do you need to stay in the house 10 years to realise the value of the solar ? Research has shown that more often than not a well installed system adds more than the system cost to the house...... Not like the old rent aroof schemes which rendered your house nearly un-mortgagable !

@andybrad did you get 6kw panels and a battery for the 9k? If you did, which county are you in?

Energy prices are going up 20 percent this year, if that continues then payback even at 13k investment is going to be sub 10 years, if however inflation mellows to 6 percent it takes quite a while longer.

only issue is the installation is a lot more shaded than i originally envisaged so this may change. I wont know till march.

TBH any shading is a sizeable problem - I hope you had micro-inverters installed.

Energy prices are going up 20 percent this year

Or maybe not!

https://www.cornwall-insight.com/drop-in-wholesale-energy-prices-sees-price-cap-predictions-fall-below-the-epg-for-second-half-of-2023/

so falling from ludicrous to just crippling - But still nothing close to what i did my calcs on pre covid ?

I use 6kw a day roughly.

11 400w pannels invertor and 4.8kw battery

In huddersfield

We looked at it last year and for a full array and battery we were looking at ~15 year payback. Probably down to 12 years now with current electricity prices but then the panels have probably gone up to compensate.
Not worth it for us

I have a 7.5 kWhp array and a Tesla Powerwall. We don't export any so if I take the annual system production at the current electricity price cap then the installation will take about 10 years to pay back. However the battery means I run the house on off peak from Octopus Go during the winter saving me between £150- £200 per month bringing the payback down (to what I haven't bothered to estimate). I figured the savings would be greater than any interest if I invested the money and so far I'm right. Plus, if you can afford it, its just the "right thing to do".

I wouldn't obsess about the financial case too much. When did anyone ask you what the payback period was on your nice new kitchen, conservatory or MTB?

However the battery means I run the house on off peak from Octopus Go during the winter saving me between £150- £200 per month bringing the payback down (to what I haven’t bothered to estimate).

Just having the smart meter installed as I type (on 4G as house is offline) so we can do just this.....

Uponthedowns - i assume you had that installed some time ago?

Andybrad, who did your install ? as i'm huddersfield and wanting a quote

@footflaps is the differential in current “economy 7” tariffs enough to actually make this worth while? And not offset if you use more than the battery capacity

@footflaps is the differential in current “economy 7” tariffs enough to actually make this worth while? And not offset if you use more than the battery capacity

Octopus offer a range of dynamic tariffs inc some where they pay you to use electricity if the grid is overloaded.

I guess it might save a few £100 over the year maybe...

Unfortunately for me I think my daily consumption must be around 13kwh so would need a much bigger battery to make that an option

For those with panels how efficient is the conversion - on a sunny day do you get the full 4kw (say) from a 4kw array. On a bright and sunny autumn/winter day do you get reduced generation when the sun shines (I know overall less generation will happen as days shorter)

You will never get 100% of the rated generation as there are many variables (aspect, inclination, clouds etc) but you can get fairly close.
For example on June 10th my 3Kw S facing system on a very sunny day produced 22Kwh of power with the peak being at 2:10pm.

In the winter not only are the hours of daylight much shorter but the sun is much lower in the sky and your panels are unlikely to be optimally angled for this.

That said, at my main house I have a 4Kwp array facing E/W which is good in the summer but loses out (comparatively) in the winter due to the low angle of the sun. I'm hoping to add a further 2Kwp array which will be ground mounted and optimised for winter, so S facing and quite steeply angled.

You can get a prediction based on a given system, it's location and orientation eg for ours:

From here: https://re.jrc.ec.europa.eu/pvg_tools/en/

[url= https://live.staticflickr.com/65535/52437382441_babd24d272_z.jp g" target="_blank">https://live.staticflickr.com/65535/52437382441_babd24d272_z.jp g"/> [/img][/url][url= https://flic.kr/p/2nTHhUH ]PV output[/url] by [url= https://www.flickr.com/photos/brf/ ]Ben Freeman[/url], on Flickr

So far we have exceeded the predicted yield considerably - but if the predictions are given following MCs guidelines then that should be the case.they are not allowed to over egg.

Peak I've seen is 29kWh from my 4.14kw system limited to 3.6 at inverter .... With 25-28 being quite consistant march-april-may .....

Uponthedowns – i assume you had that installed some time ago?

Initial 14 panel solar array installed October 2021, further 6 panels installed May 2022 and the Powerwall was installed Sep 2022 after waiting 1 year from ordering it!

£16k System with a 13kWh battery

We use 6500kWh/y which including the day rate is £2500/y at current rates.

Using the battery and overnight charging in the winter and exporting a little in the summer, we expect our annual bill to drop to around £300. We also expect to be able to use the excess solar in the summer to eliminate our oil use, thus saving about £500/y in oil - again at current rates.

This is an annual saving of around £2700, so the ROI would be around 6 years. We also had our house valued and rated after the install and it has added value and improved the EPC rating.

A friend of mine does ev charge points and solar installation. Give him a look up at charge point solutions Oxford for a quote
www.chargepointsolutionsoxford.com

It will be interesting to see what the reality is Daffy.
That's an awful lot your expecting to take off your leccy bill (and the oil for that matter)!

@daffy which county are you in? That sounds quite good deal.

@footflaps that looks very useful. Is there an easy way to work out the azimuth angle of my roof though?

Thanks Robbie, I’m in Surrey so probably out of catchment.

they are not allowed to over egg

Im used to taking any prediction with a pinch of salt but this came through loud and clear from the quotes I received. The figures they use are staggering if they are anywhere near accurate.

That’s an awful lot your expecting to take off your leccy bill (and the oil for that matter)!

The battery makes all the difference to the utilisation.

I'll check and see how far he travels for install 👍

I viewed my Solar PEV system and battery install as a sunk cost so didn't worry about how long it would take to pay back the "investment" or consider it in any way as requiring a business case to do it. The real question was "could I afford it and was it worth doing?"

Its a saving and has a major environmental benefit which has no actual monetary value (well, it does actually) but a major societal one as well as some large scale eco-smugness to boot 🙂

To be honest I justified the cost by taking into account the fact that, due to covid lockdowns and home working I had avoided commuting into London for over 15 months so took the saving on train fares (damn you Southern trains!) and "spent" this on the solar panels, it didn't cover everything through as I bought a battery as well.

On day one of operation we reduced our electricity import from the grid by two thirds. Our current average total import power from grid is 40% of total usage. Spring and summer should reduce that even further.

4 months from the system being commissioned and it looks like the years savings on my electric bill will be £800 to £900 (at current prices) and whatever I get from the SEG grant (which looks like about £90-100-ish for the year or a bit more if the spring/summer is sunny but we'll see ).

With the some back of fagpacket calculations I have a payback period of far, far less than 10 years on my system. oh and the aforementioned environmental benefit

What having a solar PV system does is it insulates you a bit from the fluctuations in the prices which is going to continue over the next few years at very least. And then there's that minor issue of the environment.

Provided you can afford the initial outlay for a solar PV system and provided that it is suitable for your house/home, whatever business case there is, is so clear its basically a no-brainer

Muddy@rse - I don’t disagree with what you say but I guess you could make other choices with the money that are environmentally friendly too - eg buy locally made food/durables etc. also one thing I do wonder is what are the implications environmentally of more and more lithium barriers being produced to sustain this greenness (solar and ev cars). Not saying I think Solar is bad but might not be a totally free lunch.

kWH used in 12 months preceding solar was 4200.

With solar a full 12 months was 2200.

Let's see what 12 months with battery brings.

October alone with nothing in 2021 we used 389kWh. went to 299kWH (with solar alone - 180kWh generated) to 83kWh with solar + battery .....we generated 250kWH of solar.....

It probably isn't a free lunch. But having solar and batteries doesn't mean you don't need to buy locally and use durables....they are not mutually exclusive.

@Sharkbait I have installed solar PV for a living since 2010. Daffy's system sounds similar in size to my own system. I am getting similar savings on our electricity bill.

As trailrat said - the large battery makes ALL the difference.

@saintsludge do you have any experience of lux 5 hybrid inverters?

@muddyjames
He is happy to travel. It will just be built into the quote so give him a shout and see if it's any use to you👍

@footflaps that looks very useful. Is there an easy way to work out the azimuth angle of my roof though?

Just take a look and guess? Or take a photo, then count the rows (width) and columns (height) of bricks and from that you can calculate the pitch exactly...

Thanks. I guessed the pitch, I wasn’t sure how you converted the direction the roof faced into azimuth (when I first did it I left the box blank but that effectively assumed south facing so overststed things!) but think I’ve worked it out now.

Very useful as helps give a better idea of what of the annual production might be used.

I do wonder is what are the implications environmentally of more and more lithium barriers being produced

Some context. By 2030 the lithium market will be between 20-60 million tonnes per annum. We currently dig 4.5 billion tonnes per annum of coal out of the ground and extract a further 8 billion or so tonnes per annum oil and gas burning most of it. Oh and don't forget 2.5 billion tonnes per annum of iron ore. Compared to that little lot lithium mining doesn't touch the sides. Lithium is also recyclable which fossil fuels aren't (unless you want to grow trees and bury them in the ground for a few million years)

I am just about to get 4.75kw of solar and 7.1kwh of storage for £9,950

I drive an EV and my bill for the year on Octopus go is looking like £2,000

I forecast that this will come down under £500, helped by the ability to charge the batteries on Octopus go and therefore arbitrage daily use even in winter from £0.40/kwh to £0.12/kwh

Payback time should be around 6-7 years

I am just about to get 4.75kw of solar and 7.1kwh of storage for £9,950

That looks like very good value...

We paid £12k for Nine 425W panels and a 10 kWh battery.

So… from an Australian point of view, this is really interesting. I’ll start off with my original calculation. I spent AUD $8000 on the first install - so around 5500 gbp. With that I broke even last year (around 4-5 year ROI) however, times are changing fast. I followed up with a powerwall install a year ago as the landscape has changed significantly since the first lot of solar went on. The key issue here is with behind the meter (distributed PV) generation. Originally, solar was a great investment as there was guaranteed infeed rates so even if you didn’t use it, you could feed back to the grid and get a return. Now the situation is different and may be an indicator of what might be in store for the uk. The situation now is that rooftop PV generates so much output that the grid is overloaded. The distribution networks have taken to either increasing grid voltage to force inverters to switch off, or the newer systems are built in with a function to allowed them to be switched off remotely when the grid has excess feed in. To boot - the infeed tarrifs have also dropped too close to nil.
So, as solar PV gains ground, we find that the necessity of having a battery increases as the dramatic swing from day to night places increasing strain on generators, and therefore peak pricing becomes more polarised. Now - if you don’t use it yourself, it’s really worthless.

Originally, solar was a great investment as there was guaranteed infeed rates so even if you didn’t use it, you could feed back to the grid and get a return. Now the situation is different and may be an indicator of what might be in store for the uk.

It's much lower now that it was. 15p at the moment and for a couple of years I think it was zero...

Was very high 20 years ago in the early years and those system made their owners a handsome profit over the years, but probably cost nearly £15k to install back then.

Was very high 20 years ago in the early years and those system made their owners a handsome profit over the years, but probably cost nearly £15k to install back then.

10 years ago when i first looked they wanted 15k for a 2k install....

id have made money on the FIT - but it was hopeless for powering my house and took up the same roof space as my current 4k system.

a 4k system came in at 4700 installed 18 months ago.