Solar Panels

[Barryboy]

I am seriously considering having panels fitted and will soon be having a zoom meeting with a supplier/installer company. I know that a lot of you guys have panels and would be grateful if you would let me know what sort of questions I should be asking. In truth I am more concerned with minimising my home electricity bills (current consumption approx 3800kwh/year) than selling power to the grid and would be grateful for any hints/tips.
Rob

[pacifichrono]

Hey Rob,

I've had solar panels installed on my home in San Diego, CA for about four years.

These would be some of my questions:

• Do you warrant both the labor and equipment, and for how long?
• What brand of panels do you use and how do they compare to competitors?
• What is your company's reputation rating by independent reviewers? [in the U.S., this would be Yelp and/or the Better Business Bureau (BBB). You might also Google "best solar installers in my area" and read user reviews]
• How much extra would it cost to add a storage battery (e.g., Tesla) at the same time?
• What is the estimated payback time (break-even) to recapture the costs of the panels, and the battery?
• Does the government subsidize my costs through tax credits or otherwise?
• What software do you provide so I can monitor my solar energy capture and my usage?
• Can you provide me with the names and numbers of your recent customers as references?
• Will you repair my roof if the installation causes damage (like water leaks)?

Our gross cost four years ago to equip our 2600 sq-ft home was about $22,000. I don't know if you would require more or fewer panels due to your less sunny location.

Good luck, Rob!

Tom

[Franky Four Fingers]

Thats quite a difficult question, the biggest one for me is having the cost Vs the size of the array and whether or not you’ll take advantage of the power you generate when the conditions are optimal. Theres little point having 3kw sat on your roof and you not being there all day- you need to harness what you produce.
Im guessing the average install for a reasonable sized array would be around 6k-8k so you need to work out the maths.

[MartynJC (UK)]

The installation position is important.

Panels are installed in strings and the panels in a string work in series. (Unless you have micro inverters under each panel which may be an option in UK). This means if any one panel is shaded by a tree or chimney the whole string operates at that lower power outage.

A good installer can advise on the best position - but they need to have a site visit - all else is theory though some installers say they can do it with simulations it may not show the current growth of trees etc.

get 2 or three quotes.

I would go for German brands like Kostal, SMA etc rather than Chinese Growat even though Growat is cheaper.

Take ROI with a pinch of salt especially with the UK weather. (I assume you are in UK?).

Batteries - cost a lot and it’s questionable if they ever pay back what they cost. A BYD batter pack is maybe 9000€ that will pay for a lot of electricity even over 10years. Considering you don’t want to charge it to over 80% and drain under 10%.

A good installer with work out a payback period for different systems.

Maybe try with a smaller (cheaper) 4kw system to start with - see if that gives expected results (returns). Then invest more - more panels and perhaps a battery set - to take you to say 6kW.

Panels typically are quoted at 640W for a mono split panel. 5 panels is a minimum,

Personally - we have been quoted 9 as a start size and optimal 16 - but we can’t fit that many on our best site so going for 14 - 9KW nominal

our 14 panel setup is quoted as 13,000€ or so (plus 3000€ for a garden structure). No battery. We are home all day and a big drain in the summer is pool pumps and heaters and also irrigation pumps. In the winter it’s air-air heat pumps.

one advise is switch to dual tarrif and run your big items (emersion heaters, washing machine, cookers etc) in daytime when the sun is shining and only run lights and so on in the evening)

[g40steve]

Why is the company doing a Zoom call?

Are you at home during the week, if yes the numbers might work for you?
If not you get pennies to export what you don’t use & ROI will be stupid.
Be aware it’s a bonanza out there currently in the UK & demand is crazy & supply slow.
This leads to crazy prices & panic. I had my full system fitted back in July & total £9.2k, recently neighbour’s have had installations & these have been 13k +!
Tesla waits are terrible my friend has been waiting since July & currently looking at March.
Beware of guarantees, will the man in the white van really back up the warranties in the future.
I decided to go with my energy supplier, at least if it all goes wrong I know I have comeback.
Batteries, I have a 5KWh Puredrive (British) battery & this covers all my needs overnight, surprisingly on these crisp cold clear days I get a full battery by 2pm.
Inverters, do some research, I have a Solis.
Panels, Eurener 375w X14, Spanish brand used widely in Europe.
Solar immersion, Eddi, dumps used energy into hot water via your immersion, but check, is yours modern or old tank, better if immersion is middle or bottom.

So Energy have an online Solar portal & you build your system from this. The images allow you to mark roof outline to gauge how many panels & importantly any obstructions.
If you are happy with initial quote a £99 survey fee follows refundable if you proceed. The surveyor spent & couple of hours checking locations for cabling, battery sites, the amount of scaffolding required, supply boxes, distribution board, roof structures & conditions, elevations & positioning of house to sun.
Final price for job then follows.

For me it was not all about ROI, I wanted to do my bit & try & go slightly green.

[BillyCasper]

South facing roof, recently had panels, battery, inverter.

Shortage of labour and materials. Ours was scheduled for July. Scaffolding went up in October, work done in November, scaffolding was taken down this month. Always difficult to get hold of anybody and messages left, never answered.

Ask how it affects your existing meter readings, billing and if it needs replacing and if yes will it be done at the same time.

We expected a Smart meter which we don’t have yet. The meter reading in the cabinet on the side of the house has doubled rather than halved. We’ve been charged for this. Something is not right and I suspect we have a nightmare sorting this out between the power, network and solar panel suppliers.


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[Mick P]

Thats quite a difficult question, the biggest one for me is having the cost Vs the size of the array and whether or not you’ll take advantage of the power you generate when the conditions are optimal. Theres little point having 3kw sat on your roof and you not being there all day- you need to harness what you produce.
Im guessing the average install for a reasonable sized array would be around 6k-8k so you need to work out the maths.

This sums it up completely. At the moment solar panels are good for the UK but not so good for the person who installs it.

I have a large roof that faces south to the absolute degree with no trees to block out the sun. I am the ideal person to have solar panels installed but even today the payback would be about 10 years and that assumes no panels break down.

The favourability will only be tipped in favour of home installation when there are batteries being produced that are small, easily installed in the domestic market at an affordable price. Until then you will be better off staying as you are.

The only argument at the moment for solar panel installation is that you are less dependant on the grid but until we can have our own batteries, we will never be totally independent in time of high demand when we really need it.

[M4tt]

The previous owner had it done back when the subsidy was 43P and it brings in a tidy sum. The law recently changed so that you can exceed the max amount, in my case 4KWH, without penalty. In the summer it peaks at about 4KWH and in the winter at about 2KWH, which is definitely helpful. I'm seriously considering doubling it, so it's 4kwh in the winter and 8KWH in the summer. because that would pretty well eliminate my bill and maximise the money coming in. I'm unsure about a battery at this point as they don't last that long compared to the panels which seem pretty well indestructible.

[garmee]

I am seriously considering having panels fitted and will soon be having a zoom meeting with a supplier/installer company. I know that a lot of you guys have panels and would be grateful if you would let me know what sort of questions I should be asking. In truth I am more concerned with minimising my home electricity bills (current consumption approx 3800kwh/year) than selling power to the grid and would be grateful for any hints/tips.
Rob

I had my setup installed on Feb 11th, 2022. It's a 6.5kW system with a Tesla Powerwall II. I'm in the NE of England, with a SSE facing roof and it has been fantastic. As it stands, I have generated ~169% of my usage, with a usage very similar to yours (see screenshot below). It may not work for everyone (and there are some considerations to take in to account) but I'm on the Octopus Energy Tesla plan, which means that I export and import at the same price. This means if I over generate at one part of the day (or year) I can pull back from the grid at a later time at the same price per kWh. Some of the considerations with this plan are the standing charge and the fact you allow them to top up your powerwall and pull back at peak times, which costs cycles.

Before I switched to the Tesla plan, my Octopus Energy direct debit was due to be £238 a month (gas and electric). I took £450 credit back on May 26th and I reduced the DD to £10 a month. I'm currently £112 in credit (I've not topped up or anything). I intend working everything out once I've been on the Tesla plan for a year (end of March) but I expect I will have saved ~£2.5k vs that £238 a month I would have been on.



It's worth noting that the Tesla batteries are very difficult to get hold of at the moment, so a like-for-like setup might be tricky to get right now.

Getting a battery increases the costs significantly but it also makes it a huge amount more effective in terms of what you can actually use. I also disagree with a lot of people and installers - I think the bigger the battery the better.

[gunner]

I'd say a home visit and survey is a must - we've ended up completely changing the number and position of panels.

Battery is an expensive addition but we've gone for it to bridge the gap between production and use and give a bit of protection from power cuts!

[tertius]

The previous owner had it done back when the subsidy was 43P and it brings in a tidy sum. The law recently changed so that you can exceed the max amount, in my case 4KWH, without penalty. In the summer it peaks at about 4KWH and in the winter at about 2KWH, which is definitely helpful. I'm seriously considering doubling it, so it's 4kwh in the winter and 8KWH in the summer. because that would pretty well eliminate my bill and maximise the money coming in. I'm unsure about a battery at this point as they don't last that long compared to the panels which seem pretty well indestructible.

I think you mean kW not kWh?

i.e. peak output from the system is about 4 kW?

My system is 4.32 kW (12 panels) but that is the theoretical maximum output assuming 100% efficiency which you won’t ever see of course. On a good day in summer it will generate about 25 kWh, on a normal day in winter I’m lucky to see 1 kWh!

For the OP: I think the key questions I would raise are:
1. What is their ongoing support like - including advice not just sorting actual problems - can they refer you to real customers you can talk to? Or can you find some independently (better of course)
2. What is a realistic expectation for generation and how will it change over the year - see my comment above re. the difference between summer and winter. The main reason I see such a difference is the lower angle of the sun, and some trees that obscure the panels at that low sun angle
3. re. batteries consider your consumption profile and how it will fit to the generation profile - typically panels generate during the day but you use most at night - a battery allows you to store during the day and use it later. As there is no meaningful feed in tariff these days you’ll basically be giving away the excess. If you can try to shift consumption to the daytime when you are generating - dishwasher and washing machine and so on.

Like others my main objective was not financial but to feel I was contributing a bit to the environment.

Forgot to say I have a battery - 7.2 kWh vs my average daily consumption of 8 kWh - ideally I’d have a bigger battery, say 12 kWh so you have more than a day in reserve in the event of some crap generation days.

Also noted some comments about power cuts - note that your system has to be setup with the ability to isolate itself if it is to continue to provide power in the event of a power cut. Most systems will not do this and so they power off as there is otherwise a risk that they will energise the grid while it is being worked on.

[MattH]

The previous owner had it done back when the subsidy was 43P and it brings in a tidy sum. The law recently changed so that you can exceed the max amount, in my case 4KWH, without penalty. In the summer it peaks at about 4KWH and in the winter at about 2KWH, which is definitely helpful. I'm seriously considering doubling it, so it's 4kwh in the winter and 8KWH in the summer. because that would pretty well eliminate my bill and maximise the money coming in. I'm unsure about a battery at this point as they don't last that long compared to the panels which seem pretty well indestructible.

When did the rules change ? When my system went down last year and I was concerned I would need to replace the panels - I would have had to inform the FIT company on any changes to my system and they would prorate the payments to exclude the additional generation.

Had panels for 11 years - it earns about 1000 a year as its in the old “good” fit payment scheme. No batteries so if I was not working for home most of it would just go to the grid.

It was worth doing for the payments - but its probably just about paid for itself now.
But if things go wrong there is no cheap fix. Had to replace the invertor once, that was 1k and then the system just stopped working. Seems a connector to one of the panels had split and failed (over the years) under the panels which then took out the string.
It was a quick fix - the guy just had to replace the connector! - but it still cost 1k for the scalfolding to be put up so that the panels could be worked on.

Lots to think about for new installs today - they are cheaper to buy - but the subsidy is not there in the same way now. And of course in the winter be prepared for the system to generate nothing - other than odd days.

cheers

matt

[gunner]

Also noted some comments about power cuts - note that your system has to be setup with the ability to isolate itself if it is to continue to provide power in the event of a power cut. Most systems will not do this and so they power off as there is otherwise a risk that they will energise the grid while it is being worked on.

Yes, I think it's a common misconception and one I certainly hadn't realised until recently.

[Franky Four Fingers]

OP- how do you heat your water, by gas or electric with either an immersion or electric boiler?

There’s instant wins to be had with solar by it running your house throughout the day or at least taking a chunk of your consumption away. Unless you can store that electric or divert it to something that can use it like an immersion heater you’ll be sending electric back to the grid for peanuts.

My main issue with solar is that it makes a lot of sense between March and September then the benefits start dropping off rapidly as the weather declines and the nights draw in.


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[g40steve]

Re power cuts, no battery & solar should power your home during power cut without additional wiring usually called ‘Island mode’

In the event of power cut your isolator will shut down so you are not sending to the grid, in Island mode the house senses the cut & switches to battery & solar but cuts ties to the grid.

[garmee]

Yes, I think it's a common misconception and one I certainly hadn't realised until recently.

My system does take over and continue to power the house while there's a cut. Depending on the type of cut, it can take over seamlessly or sometimes I have about a 4 second gap before it kicks in.

[gunner]

Yes, mine will too, I just meant that it's easy to make the assumption wrongly.

[Barryboy]

OP- how do you heat your water, by gas or electric with either an immersion or electric boiler?

There’s instant wins to be had with solar by it running your house throughout the day or at least taking a chunk of your consumption away. Unless you can store that electric or divert it to something that can use it like an immersion heater you’ll be sending electric back to the grid for peanuts.

My main issue with solar is that it makes a lot of sense between March and September then the benefits start dropping off rapidly as the weather declines and the nights draw in.


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Heating and hot water by gas boiler. It's a 3 bed detached built in 1980. Current annual electric consumption is about 3500 kwh electricity plus about 720 cbm (say 7900-ish kwh) gas plus OFC the standard charges of a little under £28/month. My current EDF tariff is 37.43 pence/kwh electric and 11.306 pence/kwh gas. Just had a long talk with a company called Solarfast who recommend 10 x 405watt panels with a15year warranty on panels and 10 yr warranty on the inverter and cost (subject to survey) of 7729 fully inclusive. That is without a battery which comes in at about 4K extra.

Now the battery sounds expensive but without it any power that my house does not consume will be fed straight into the grid and EDF's current export tariff is only 3 pence per kwh, so even at peak summer performance (which I believe is pretty much never) and no consumption by the house EDF would pay me 36 pence per 12 hour day. So given that my main consumption time is the evening when lights, TV, computer etc. is all running, the 4K doesn't all of a sudden sound too bad. Now I will obviously go elsewhere for more quotes but grateful for any thoughts...

Rob

[tertius]

Heating and hot water by gas boiler. It's a 3 bed detached built in 1980. Current annual electric consumption is about 3500 kwh electricity plus about 720 cbm (say 7900-ish kwh) gas plus OFC the standard charges of a little under £28/month. My current EDF tariff is 37.43 pence/kwh electric and 11.306 pence/kwh gas. Just had a long talk with a company called Solarfast who recommend 10 x 405watt panels with a15year warranty on panels and 10 yr warranty on the inverter and cost (subject to survey) of 7729 fully inclusive. That is without a battery which comes in at about 4K extra.

Now the battery sounds expensive but without it any power that my house does not consume will be fed straight into the grid and EDF's current export tariff is only 3 pence per kwh, so even at peak summer performance (which I believe is pretty much never) and no consumption by the house EDF would pay me 36 pence per 12 hour day. So given that my main consumption time is the evening when lights, TV, computer etc. is all running, the 4K doesn't all of a sudden sound too bad. Now I will obviously go elsewhere for more quotes but grateful for any thoughts...

Rob

I assume the reason for 10 panels is that is the number that can be fitted in? As I would say that is a slightly small system (roughly 4 kW) for your average consumption (9.5 kWh per day). For comparison mine is a 4.32 kW system with average consumption of ~8kWh per day and mine is “OK” but wouldn’t turn down another few panels (if I had space). My battery is 7.2kWh but that is a bit small - I reckon you want c. 120-150% of your daily average consumption.

As you have identified your issue will be the mismatch between generation (daytime) and consumption (evening/night). A battery will allow you to offset the mismatch by storing during the day and using the battery in the evening/night.

You should also do why you can to shift any “flexible” consumption to the charging hours - washing machine, dishwasher, etc..

What is the battery capacity they have proposed for £4K?

[Pretzel]

We had 18 PV panels fitted to a South East facing roof in November (7.11kWp) together with a 6.5 kWh battery. Even at this time of year on a reasonable day we generate 5kWh and in todays winter sunshine for example managed 16kWh which means battery is at 100% which will be used this evening for cooking, lighting, TV and router etc. (173kWh generated so far in January)

Since installation we have generated a total of 375KWh of which about 50kWh has been given to the grid (FOC) as we were not able to use it.

In the event of a power cut, we have one double socket in the house which will run from the battery if there is any power in it. We run the battery down to 10% although it is possible to run it lower.

As an investment, the way it's currently used it should pay for itself in about 10 years, depending on energy prices. Pay back would obviously be quicker if we had an electric car (unlikely as serious Petrolheads). If we decide to sell the house, having EV charging capability is likely to be beneficial so you could argue that it's an investment.

According to our 'App' since 22nd November we have saved 150kg coal and reduced CO2 emissions by 374kg. We have also allegedly saved 21 trees.

[Franky Four Fingers]

Heating and hot water by gas boiler. It's a 3 bed detached built in 1980. Current annual electric consumption is about 3500 kwh electricity plus about 720 cbm (say 7900-ish kwh) gas plus OFC the standard charges of a little under £28/month. My current EDF tariff is 37.43 pence/kwh electric and 11.306 pence/kwh gas. Just had a long talk with a company called Solarfast who recommend 10 x 405watt panels with a15year warranty on panels and 10 yr warranty on the inverter and cost (subject to survey) of 7729 fully inclusive. That is without a battery which comes in at about 4K extra.

Now the battery sounds expensive but without it any power that my house does not consume will be fed straight into the grid and EDF's current export tariff is only 3 pence per kwh, so even at peak summer performance (which I believe is pretty much never) and no consumption by the house EDF would pay me 36 pence per 12 hour day. So given that my main consumption time is the evening when lights, TV, computer etc. is all running, the 4K doesn't all of a sudden sound too bad. Now I will obviously go elsewhere for more quotes but grateful for any thoughts...

Rob

I ran the numbers last year before the increase and just couldn't justify batteries at that time. I was lucky as the solar was installed by the builder and so not paid directly for them as such. I got a hefty discount on the asking price and so i see the Solar panels as free.
My system is only 2.4 kw (8x3) but i have the space to probably add a further 8 at-least knocking my system over 4kw but again my man maths isnt working in favour. My house is entirely electric and have no gas in the village and we heated the water in the early days by the electric boiler which was ridiculous to say the least. When I realised i could heat the water with the immersion instead of the boiler i saved a packet and with some tweaking i saved a bit more. What i did fit this time last year was a solar iboost which diverts any excess straight to the immersion and so essential in the summer months i have a lot of free hot water.
Looking yesterday since the install its saved me 600 kwh of electric which in todays terms is saving me over 200 quid already and ive nearly broke even.
Batteries for me still dont make much sense as during the winter months you’ll be lucky to generate 1 kw all day. At times today I've been generating 20w an hour which doesn't even run the base load of the house. As i said march to September great….Oct to Feb you may get a few decent days but in general its rubbish.
You can buy an awful amount of electric for nearly 8k - todays prices thats 21k kwh of power

[Barryboy]

Thanks, all. One huge consideration is that I don't have any confidence in the stability of energy prices long term. Some say that next year (2024) there may be a small decrease in energy prices but who knows? We've had one price hike this year already and there's another due in April. If prices continue to rise the financial viability of a panel installation is improved exponentially and the more I think about it the more I think I need to move quickly or not at all.
Rob

[ernestrome]

We paid 8k for 12 panels (5.5k) and 6.5kw (2.5k) growatt battery last September. Hope that helps put your quote in perspective. I expect ours to pay back well under ten years and we don't even have optimal roof direction (ESE). OTOH we live in sunny East Anglia. if you have a battery you can also use cheap overnight tariffs to charge it during the winter and reduce your bill. We switched to economy 7 to that end and pay 16p/kWh.

Don't get sucked into panic buying from price gouging installers. Took me a good few months of research and getting quotes to find an honest company doing a proper job at a fair price. Demand is, i believe, still high for installations currently but it will not necessarily continue indefinitely and if you over pay by many thousands now it substantially lengthens the payback (obvs).
A critical and simple check is to total what you could buy the equipment for yourself at retail price and then you will quickly get an idea of that the installer is taking for installation costs. What's reasonable for a day or two scaffolding hire and the labour? I went back to some quoters with the figures and they did not like it up them Pike.

Do not rely on other people's calculations until they show their working. There are a lot of know-it-alls regarding solar (and EVs) who know less than they think. It's human nature to convince yourself you made the right decision, whether that was to purchase or to pass on it.

[Andyg]

Assuming you have the right slope and direction of roof, it’s a bit of a no brainer. My system is 19 panels, two inventors and a Tesla Powerwall2.

Using my 2022 data.

Used 4451kw (about 12.5kw/day)
Generated 4551kw
Imported 297kw
Exported 164kw.

The original system was installed in 2011. Since then I have replaced one inverter, but had no issues with panels, roof, etc.

If you are going to do it, make sure you invest in a battery.

[Kingstepper]

All this talk of panels - are they a standard size or power?

[sweets]

The other thing to ensure you have is a switch that senses when you have an excess of electricity (over usage and battery charging), and diverts that to your immersion heater to reduce your heating load. Solarimmersion do one, but others do too.
It saves you exporting electricity for very little (financial) gain, but then importing other heat (gas or whatever you use) at a higher price. This works best if you have a very well insulated cylinder, and time your heating so that the solar can so more.

[tertius]

All this talk of panels - are they a standard size or power?

Basically yes, for domestic installations. I think the most common output has increased from 360 to 405 watts in the last couple of years.

[ernestrome]

Basically yes, for domestic installations. I think the most common output has increased from 360 to 405 watts in the last couple of years.

I would say basically no, but they vary within a reasonably small range. For example you can find that a marginally smaller panel allows more in total to be fitted on done roofs.

[drmarkf]

Excellent info in this thread, but 2 points that I don’t think have been made yet:

Do shop round for your export contract: yes, it’s peanuts, but it’s 5.6p per peanut at the top end (we’re with Scottish Power) but 0.1p with British Gas and others.

You don’t have to contract with the same company that supplies you, although some will pay a higher export rate for their supply customers.

Also, some local authorities have arranged group buy schemes in various counties. Eg Cambridgeshire and Norfolk went with Solar Together, and this does bring some VAT savings etc. We and several local friends are very happy with our installers via that scheme (Greenscape in Ipswich).

Yes, for decades it’s been said that adding solar panels etc to a house doesn’t increase its value, but that’s clearly bananas now: carefully checking the utilities bills has become a much more important part of house purchase by any sensible person.

[Andyg]

All this talk of panels - are they a standard size or power?

Mine are old. Standard Size Mono-crystal and about 350W.