Solar Installation

[Doug99]

Hi Guys/Gals
I'm looking to install domestic solar system and wondering if anyone has advice on the process.
Since making initial enquiries, I am inundated with information!!
It seems that suppliers are using google maps to calculate my roof space and already I have been quoted maximum of 7, 9 and 11 panels.
A quick browse of some T&Cs suggest a price is quoted, I sign a dotted line and then a surveyor visits to establish detailed specs.
I'm not one for committing £££s before a detailed spec.
Has anyone on the forum purchased a system recently and able to share their experience both good/bad?
For Info:
Detached House
3 Adults
Latest elec bill shows estimated 3600Kwh/year
Considering a 3 or 4Kw system with 4 or 5Kw battery.
Current elec provider is Octopus.

Cheers All

Doug

 

[nero44]

Hello,
you definitely do not need to sign anything before having a firm quote. They all use the same software/webinterface where they enter all the information and the system uses some satellite database for roof size and and exposure, make some inferences and then have all the payback automatically calculated. I asked 3 firms and the quote spec/layout almost all looked the same (not same price though).

These "desktop" quotes are just an indication and most companies offer a free real survey in person. The company I ended up also was hoping to get 11 panels up there, but after the onsite visit with actual measurements it turned out I could only get 9.

My system was installed in December 2023 and so far I am very happy. 9 x 430w + 3.6kwh hybrid inverter + 7.5kwh battery system (they suggested 5 but I opted for a bit more). I am on Octopus Flux and have so far only relied on using solar+offpeak. i.e. I never ran out of battery and had to use peak grid import rates. My battery recharges off peak overnight each night.

My general pointers would be:
- ask for 2-3 firm quotes with actual onsite visits
- go for a reputable company that can demonstrate that they already have commissioned many systems. Companies that show off their work on website and social media (and thus are proud of it as they open themselves up to scrutiny) often do clean and good work. Word of mouth recommendation even better if you have any neighbors with similar installs
- make sure to ask if scaffolding is included
- think about unrelated roof repairs/fixes whilst you have scaffolding up.
- do some research on panels and batteries. Ideally reputable companies, which have a support or operations in UK or EU

 

[Murdochcat]

Beware of "hidden" extras - like you shouldn't have PV on a shared RCD

Etc , etc

 

[ericmark]

Beware of "hidden" extras - like you shouldn't have PV on a shared RCD

Bird nest protection was one they tried on me.

Main gain is the battery, I went for 14 panels, an inverter, and a 3.2 kWh battery, I see 5 kW some days, but also had bad days, the two patterns are top 3.2 kWh battery, and below 6.4 kWh battery. The battery does three things, one it bridges the gaps when a cloud comes over, and two it allows use of off-peak during peak times, and three it allows selected items to continue working when you get a power cut. In my case, central heating and freezers.

So I would say look at your daily minium use, not worried about using shower, washing machine, dishwasher etc, as you can adjust your times when you use them, so looking at my usage rarely below 10 kWh per day, so I need around 5 kWh of battery, since 10% held back for emergency use, my 6.4 kWh is 5.76 kWh useable, maybe not quite enough in heart of Winter, but more than I need in the summer.

Look as purple line the state of charge, that day we got very little solar, the 16th but to have batteries big enough to cope with that, not likely to get your investment back, next day more typical and the second flat top is where I was exporting, 4.5 kWh that day. And still after a year not being paid for export.

The tariffs are not as straight forward as I thought, I ended up with British Gas, due to one before going to the wall, and they like many others offer more per kWh exported if you use them for both import and export. And they also would allow me to have an EV tariff even without an EV, where Octopus wanted the details of the vehicle and charge point before you can have the EV rate.

So not comparing like with like, but Economy 7 with EV and British Gas EV rate is far better to Octopus Economy 7, I likely will move to Octopus once my tie in with British Gas ends in April, there is also how long the off-peak runs for, mine is 5 hours, and since I can't find out is BST or UTC I only use 4 hours, which is ample to recharge battery and when solar has been bad, run the three items with timers, dishwasher, washing machine, and tumble drier.

I had an iboost+ fitted, and until I get payment for export, that is saving me money, but summer typical I use 2.5 kWh per week for DHW so not that much, and once I get paid for export the payment for export is more than the cost of off-peak, so a simple time switch would work better.

I pay with standing order, idea is over pay in summer, to cover for winter, before solar was paying £173.90, dropped to £119.70 with solar, and dropped further to £81.35 when off-peak started, but seems not dropped enough as now have balance of +£984.36 and September including standing charge £59.45. Now with second battery will cost even less.

The lottery is what the weather will do, if I know bad weather then three machines (washing machine etc) run overnight, but saving more if using the solar, so if we think going to be a good day, run in the morning and discharge the battery more, and let it recharge in the afternoon, do not want to start any running after 3 pm and then will not start evening with full battery.

 

[Murdochcat]

^^

Mesh around the panels is essential IMHO

 

[ericmark]

My solar went in 7th Sept 2023, since then used 5930 kWh and the solar has given 5660 kWh, but 2732 kWh exported, so draw from grid was 3688 kWh, the battery had transferred 1494 kWh and was 3.2 kWh as my system allows 1 - 4 batteries of fixed size, and started with one, now gone to two batteries.

What would be of interest is how much peak power used, but the apps don't show that, I have a excel program to work it out, but once I was convinced a second battery would pay for its self, I stopped using it.

The problem is when the power is used, needs manual intervention, and Anglia Rippon may do her gardening at night using off-peak, but I want to do it in daylight. And don't use much power in my garden anyway.

My bills have dropped, and also life style has changed, I have no qualms about using the air conditioner in the summer, if warm enough to need it, then loads of solar. And we now delay use of the three machines with timers, washing machine, tumble drier, and dish washer and run either with solar or off peak. Automated use as with the iboost+ is really what we want, but that turns out to be a white elephant.

OK we are retired, so I can at 10 am, look at weather, and decide what to do, but if I was working, by time I know what weather is like, too late.

 

[ericmark]

This is what I aim for, the battery did not fully discharge (drop to 10%) and the sun has taken over at 10 am, recharging the battery. The day before we were sitting at 10% before off-peak came in, but the time that we were exporting was short, 2.3 kWh in total, and it is the variable nature of solar which results in the need for a battery as well.

 

[Doug99]

Thanks Ericmark for your detailed charts.
I have a low roof which means I can only fit 5 panels on my south facing roof and 3 each on my east and west faces (total 11).
Feedback from potential providers have different solutions.
One option includes microinverters which ensures each panel works independently so any shading on one panel does not affect the performance of the others.
Another cheaper option states my x3 roof faces would have 3 strings of panels. This suggests any panel in the shade would affect the performance of all panels in that particular string.
Now waiting for detailed proposals to establish performances.
It will be interesting to establish whether their performance figures reflect the reduced performance of my west/east facing panels compared to my south panels.

 

[nero44]

One option includes microinverters which ensures each panel works independently so any shading on one panel does not affect the performance of the others.

I am surprised they offer solutions w/out, I thought microinverters is a standard now. They were in all my 3 proposals I received. I have no shading, but a small chimney stack that can cast a shadow.

One other thing I forgot to mention, make sure your installer is MCS approved and will provide the certification docs post install.

 

[Doug99]

This is my house with my rear garden facing south. Unfortunately the white blob on the south face is my vent stack.
Talking to providers, it appears that they use google maps to determine the m2 of each face to calculate the number of panels
( all subject to site visit obviously).
Not keen to use my garage roof as it is only single storey and is in partial shade from the neighbour's house in the morning (as shown) and by my own house in the afternoon.
Initial feedback suggests 5 panels (south face) and 3 panels each (east/west faces)

 

[nero44]

Initial feedback suggests 5 panels (south face) and 3 panels each (east/west faces)

sounds reasonable. you will get a nice constant feed as the sun moves form east to west. I have 3 panels south facing and 5 panels south east facing. so in the afternoon generation goes down quite quickly as the set of 5 gets shadowed early.

 

[ericmark]

My house all on one side, bottom left, this is 17:08 today the inverter does split in two groups, it was good early in the day, but then cloud so so batteries only at 60%, think we have 14 panels, but the aim is to reduce the grid power used, not to take it to zero. In hindsight, they were right putting all panels on the one roof, in the morning which would have been better on the other roof, the battery never runs out, it is in the evening when it runs out, so the more I can get just before sun set the better.

It seems they used some software, and clearly it was good software. The only error was my fault, I had an iboost+ fitted to heat the domestic hot water, yes it works, but I did not realise my total weekly use for DHW is less than 3 kWh, so it can only at best save £1 a week, so it will never pay for its self. Specially as only used in summer, can't stop the CH from heating the DHW, so as soon as CH running, the iboost+ does nothing.

 

[nero44]

14 panels

out of interest.. for today, what is the total solar generation today? so excluding grid charge, basically the cumulative total of your green line.

 

[ericmark]

out of interest.. for today, what is the total solar generation today? so excluding grid charge, basically the cumulative total of your green line.

is this what you are after? That is to 18:40 as said not a good day for solar, wife did run washing machine and tumble drier, not sure about dishwasher. The battery will not work in isolation, it uses the same inverter as the solar panels, but we have saved more money based on investment with the battery to the solar panels.

Or was this what you were looking for, it shows how good the morning was, and how poor the afternoon.

 

[Doug99]

Now looking to maximise the roof space by doing something with my vent pipe.
I've asked the question on the plumbing forum as to whether a plumber or roofer would offer solution.