The Solar Thread

Like the Electric Car Thread – Perhaps we can have a dedicated thread for Solar PV, the costs for install, the return on investment, your generation and export curves, batteries, etc.

Ain’t no sunshine in my life

We’ve inherited a 4kW array on the place we bought last year, and had the FiT moved over to us. We’ve had payments of about £600 for the year.

We also have an iSolar water heater thing, which means the (oil) boiler is turned off completely from May(ish) to October(ish), and we’re getting savvier about running stuff like the dishwasher/washing machine when the sun is shining (or, at least, during the day).

I’ll start – we’re looking to get a 12*450w in-roof array installed in August this year. Included with this will be a 10kw battery storage. The projected cost for the install is £14-16k.

Based on our current usage of 6500kwh/y we believe the array will generate about 4700kWh. We also believe that we can charge the batteries from the grid on a cheap rate to further leverage the package during the winter months.

Based on the current power costs of 30p/kWh, we think the ROI would be just under 10 years. If the batteries can be leveraged as believed that would reduce to 7 years. If the electricity price increases to 40p/kWh that could be as soon as 5 years.

We’re also looking to install solar water heating on the lower roof, but it will be west facing, not south so unsure of the return on this.

We’re also looking to install solar water heating on the lower roof

Why not just heat it from solar electric (using an iSolar thing or similar)?

Why not just heat it from solar electric (using an iSolar thing or similar)?

The cost for the solar water heating system isn’t that big and will provide additional benefit rather than taking away from what’s already being generated. We were quote £4500 (conveniently the same price as the GHG) and believe it can be had for closer to £3500 based on speaking to several companies.

Fair enough. I’d, ideally, like to do something with wind, cos it’s always windy here, but domestic wind generation seem like a bit of a non-starter.

Our solar thermal provides our hot water from May to October from just one panel (two people household). Outside that period it preheats. It thermosyphons so there’s nothing to go wrong except boiling over if I don’t take the lagging off the return pipe if we go away in Summer.

The washing machine can be fed direct.

PV 3kW from 10 years or so ago which paid for itself in about six and a half years.

Based on our current usage of 6500kwh/y we believe the array will generate about 4700kWh.

?
Why does the generation depend on your current usage?
(but your figure of about 4700kwh is about right compared to our S facing 3kwp installation which averages 3.2Mwh/yr)

Looking to get some solar on the roof of the house. Will hopefully be super-effective in spring/summer/autumn, but rubbish in winter.

Will hopefully be super-effective in spring/summer/autumn, but rubbish in winter.

FTFY

Last years number from that system

2 x roof array. Installed a few years back. FIT payments bit over £1k a year. Arrays cost c£10k. Payback should be around 10 years depending on the panel performance. Panel life is c20years so hopefully lots of money saved in the long run.

As I now work from home (plus the standard STW hot tub) I know we use all the power they generate so the 50% we get back in FIT works.

Used to worry about the figures and track them but these days just drop in the meter reading and don’t bother to really look at the overall performance.

If you are looking to have a PV array plus battery install in the near future, I would book in for the work ASAP. I was at Fully Charged Live last week chatting to several companies that specialise in this and they all were quoting 6-8month lead times with some gear more like a year.

Price of PV panels is soaring at the moment through demand, though the price of inverters and batteries are coming down through economies of scale and better tech.

Givenergy were great to talk to, not too expensive and really knew their stuff as was JoJuSolar, though they were at the upper price end.

This space is really taking off right now

Got 4.14kw on the roof last year

Cost £4700 fitted.

Don’t get FIT but do get paid 4 pence/kw but it quite literally has cut our kw usage in half even over winter. Because we lack batteries we pretty much have a fixed floor in daily use.

We also are using a solic to divert excess produced energy to electric heaters in autumn/winter. Little point to export and alternative is to burn oil…..

Looking at giv energy batteries -costs are coming down that’s for sure. When I first looked I was being quoted 12k+ for batteries…..

4.6kw array south facing, no batteries. 3.6kw inverter. Solar iBoost to run hot water. Installed mid Feb & so far generated 1100kwh & exported about 350kw. No Fit, but 5p/kWh smart export guarantee. Apart from last week where weather was terrible (Glasgow) the hw heating has been switched off at the boiler. One of us is in during the day so we didn’t see the cost/benefit of batteries to be in out favour. £5200 all in-the extra £200 over 5k was due to a long cable run from inverter to fuse box.
Last couple of leccy bills have been £25/month (post price increase) That’s down from around £45-£60/month from April last year. Not compared gas usage like for like yet, but the solar iBoost kit is a winner so far.

Parents just had 8x PV panels installed through a green home grant in conjunction with the local council. Cost them nothing so I assume the install company is going to pocket any feed in tariff. Working well so far though as the only electric they used yesterday was when the sun went in and they put the kettle on.

We also are using a solic to divert excess produced energy to electric heaters in autumn/winter. Little point to export and alternative is to burn oil…..

Tell me more…

**EDIT Actually, ignore me, it’s the same as the iBoost thing we have.

Yep same as iboost just a bit dumber and quite alot cheaper

If you are looking to have a PV array plus battery install in the near future, I would book in for the work ASAP

Wish I’d got it last year tbh on a discounted local gov scheme seeing how energy prices have risen now! – forgot to apply again this year but they were massively oversubscribed so might not have gotten in anyway.
ALTHOUGH – was chatting to someone who works for a local installer & he seemed to think there were more (national) gov schemes/incentives on the way… will try to find out more!

Why does the generation depend on your current usage?

it’s not, but I was trying to show that we might be able to cover around 60-80% of our current usage with the panels/export.

Inherited a 2.16kW system on the old FiT plus a single solar thermal panel for HW.

Trying to use all high demand devices during the day as much as possible.

Net about £1400/year on the FiT and have about 5 months with minimal heating of water needed too. Solar thermal cost £200 to service recently; very 2-3 years recommended so add that to your costs.

We’re in a new build house with 8 panels on the roof. No battery storage. We’ve been in a year but I’ve only really paid attention over the past 2 months to the solar output meter, which has been averaging 6kWh per day for the last 2 months. Obviously that will drop in winter. We have them mounted facing South East.

Looking at my metered electric usage, I estimate we’ll use about 2500kWh via that with the rest coming from solar. That’s for a 4 bedroom detached house with 2 adults.

Interesting thread and hopefully I can learn something.

Quick question. How the hell are you getting so much from your FiT? We get around £11 per quarter.

New house build 4 years old. I’ve always thought the FiT we get from EDF is low but bloody hell.

Trying to find an installer in Hampshire at the moment, those that do reply are telling me they’re too busy at the moment.
If I have the space on my roof is it worth applying for the DNO and installing an inverter larger than 3.6KW?

How the hell are you getting so much from your FiT?

FIT rates started off at about 45p when 4kW of panels cost £12k. As the cost of panels reduced, FIT reduced, until it finally stopped. Since FIT reflects the cost of the panels and was intended to ensure a payback shorter than the life of the system, you keep the rate you started with (+RPI) for the 20 years.

I’ve always thought the FiT we get from EDF is low

It makes no difference who FIT is paid through. But the export tariff varies.

Thanks Greybeard.
Makes sense I think.

Next question is, as I’m not getting any benefit from the solar panels, I was thinking of seeing if I could connect the car charger to the panels and it would charge the car during the day.

Has anyone else done this?

Let’s see if that works…….*

* Edit it did first time but best to edit to remove location……

Not bad for 57deg. North better than a kick in teeth.

accepted a quote in march for panels and battery with the removal of vat it kinda swung it for me. DNO applied for, was told this can take up to 3 month and install date of early 2023. Also an interest free loan from scot gov helped with my man maths.

Hardest part was getting quotes, everyone busy and a wait list for a survey  had a few new start up companies able to fit within a week or so. I don’t think so

Sharkbait, where do you get so much detailed info from? Is it direct from your Inverter? My Sunny Boy only provides me with very basic info. I like the way yours provides such a detailed report.

Which solar-immersion device is recommended please? We have a solar and battery system, but looking to use it to heat the hot water. Ta.

9 panels of PV (2.25kw 10 years old) and a panel of Thermal (2 months old) on the roof here.

The Solar thermal is excellent – I’m sure it’s wayyyyy more efficient in terms of roof space taken and the output gained. If I had an insulated thermal store big enough I think I’d have the whole roof covered in Solar thermal instead of solar PV.

The PV paid for itself at about 6 years on a FIT of 15p/kWh. We get around £650-750 a year from it. The inverter (and hence all the daily production data etc) is in the loft so plotting exact generation day-to-day is a complete faff so I haven’t done it.

HOWEVER, my smart meter in-house-display seems to have had an upgrade recently and can now tell me when I’m exporting to the grid. Needless to say, even after 10 years of use, seeing exactly when we are exporting the most electricity means it’s focussed our attention on running the washing machine/dishwasher during the day, as the FIT means that we get 15p/kW for generating whether we are using it or not, but if we are using it then we are avoiding paying for using of electricity at night/evening.

The Solar thermal is excellent – I’m sure it’s wayyyyy more efficient in terms of roof space

Yeah if your heating system is compatible it is much more efficient and a good way to get free hot water or at the very least reduce your energy use on the hot water.

Looked at it recently but the roi was about 13 years even with higher prices.

@flyingpotatoes We have a Zappi 2 car charger that monitors the mains and knows when we’re exporting power. I can set it to only charge when the PV is exporting at least the minimum power the car needs to charge (1.4kW for ours). Or if it isn’t very sunny I can set it to charge at 1.4kW, using mains where necessary, but boost up to the export figure if that goes higher.

But I don’t know if it would be possible to backfit that kind of thing to another charger model.

Just accepted a “solar together” offer, 4 panels + a 3.4kWh battery for 7536, which seems reasonable. Just paid the £150 for the survey so far which goes against the cost if we go ahead.

I recently got advertised this on Facebook:
https://www.solariskit.com/

Any thoughts? Looks like a swanaiblw low cost option for flat roofs etc.

@ yosemitepaul
I have two PV systems on different houses and on each inverter I have a Raspberry pi that collects data from the inverter and uploads it to PV Output every 10 minutes.
They’ve been running for about 9 years and are incredibly reliable.

The extra information is really quite handy* and PVOutput will email you if it doesn’t receive any data for a period of 40 minutes – meaning that there may be an issue with the inverter or panels (or there’s been a power cut).
I bet very few people check that the solar/inverter is actually working on a daily basis!

* Not only is it good to look at but you can use the data for other stuff as well.
For example, I have electric underfloor [controlled by a Warmup wifi thermostat] in the kitchen at my main house. There’s a script on the inverter Pi that checks the generation every 5 minutes and when it’s over a certain level it sends a webhooks message to IfThenThat that in turn sets the temperature of the underfloor to 23c – so switching the floor on – when the generation drops below the threshold the Pi sends another message and the thermostat is dropped to 16c – so switching it off.
This way I can maximise the use of the generation (also got a diverter for the hot water).

/bookmarked/

Fwiw, I’m not convinced solar thermal is cost effective. Assuming annual servicing to keep glycol topped up & pressured correctly. Then you have to factor in you’re running a pump during daylight hours. Over complicated tech that no heating engineer wants to go near in my experience. My PV to immersion boost provides me with more hw than thermal panels ever did.

I’m interested in solar PV but it’s really hard to know what’s relevant if we don’t know where you are and what kind of weather you get… will my panels in cloudy Manchester be the same as yours? Are you in London? Orkney? South of France?

Can I kindly request that anyone giving details also says whereabouts in the country they are? 🙂