Solar quote confusion 28 June 2021 at 7:48PM edited 28 June 2021 at 8:25PM in Green & ethical MoneySaving 16 replies 397 views

Cranberryberry

I’ve been getting in quotes for a solar system and wow it’s confusing! I’ve only used MCS installers and the range is huge - from £6800 for 5.4kw to £4200 for 2.9 kw. 

No one seems to quote for the same size and I’ve been trying to compare based on £ per watt (installed value, not produced) which gives me £1.44-£1.26 per watt. 

Is this reasonable? I live in a bungalow and there’s nothing odd about the roof. The systems themselves seem similar (longi or Ja solar panels). 

Any suggestions on how I can benchmark? I’d normally want quotes in a similar range but I can’t seem to get them to produce similar system designs!

QrizB

I don't know where in the country you are but even at the cheaper end of the scale, £1.26/watt seems a little high. How many quotes have you got? Can you post brief details here?

As a rule of thumb, higher wattage systems should be cheaper per watt, will have better economics and no-one ever complains of having too much solar power.

Do keep in mind that any system capable of producing more than 3.68kW will need prior permission from your DNO and this might include a fee.

Hexane

Does a bungalow installation normally mean that scaffolding is unnecessary? If so, that should make it a lot cheaper.

£1.00 per watt installed is often a benchmark to aim for. Doesn't matter if it goes a little above this...

Benchmarking by £ per watt is sensible (I went ahead with my installation partly based on that) but bear in mind that 5.4kW of panels with only a 3.68kW inverter isn't going to make full use of all the potential generation. (In the same way that for example, 4kW of panels with a 3.68kW inverter will make use of nearly all the potential generation.)

Martyn1981

I'd agree with the comments, for a bungalow a price of about £1/Wp should be doable for say 4-5kWp, and all through a 3.68kW capped inverter.

As you go bigger, the price per Wp should fall. My sister had an install last week of 10.3kWp and that was just under £8.5k (but there was already scaffolding in place).

Reed_Richards

The issue that nobody has mentioned is how much of your solar electricity you will actually be able to use.  If you are at home during the day you may, with some effort, be able to switch quite a lot of your electricity usage to times when you have solar power (although your fridge and freezer will run day and night).  Read your electricity meter a few times during the day to get a feel for how much you are using and when.  What you can't use you will have to export; the more panels the more excess to export.  But you don't get paid a lot for exported electricity so the payback time for adding more panels than you need may be long, or infinite if you are limited to exporting the standard 3.68 kW.   

Exiled_Tyke

Reed_Richards said:

The issue that nobody has mentioned is how much of your solar electricity you will actually be able to use.  If you are at home during the day you may, with some effort, be able to switch quite a lot of your electricity usage to times when you have solar power (although your fridge and freezer will run day and night).  Read your electricity meter a few times during the day to get a feel for how much you are using and when.  What you can't use you will have to export; the more panels the more excess to export.  But you don't get paid a lot for exported electricity so the payback time for adding more panels than you need may be long, or infinite if you are limited to exporting the standard 3.68 kW.   

On the flip side. The more 'over-sized' your system is the less electricity you'll have to import and pay for in the non-peak months when the panels run at a very small fraction of their overall capability.  December will usually produce about a tenth of what I get in May/June (may be even less). If I were doing it again I'd put up more panels and happily cap at 3.68kW. It's very rare for my system to hit my inverter capacity as it currently stands. 

QrizB

Exiled_Tyke said:

If I were doing it again I'd put up more panels and happily cap at 3.68kW. It's very rare for my system to hit my inverter capacity as it currently stands. 

Agreed, I wanted more but ran out of roof space!

Installing today (rather than in 2012) I'd have 11 x 370W panels not 247W ones and 4kWp on my roof.

Cranberryberry

QrizB said:

I don't know where in the country you are but even at the cheaper end of the scale, £1.26/watt seems a little high. How many quotes have you got? Can you post brief details here?

As a rule of thumb, higher wattage systems should be cheaper per watt, will have better economics and no-one ever complains of having too much solar power.

Do keep in mind that any system capable of producing more than 3.68kW will need prior permission from your DNO and this might include a fee.

I'm in the North West/North Wales border area so we should have lots of suppliers but I've managed to get a few quotes, three of which are (just realised I messed up some numbers in my original post so they don't quite match!).

Quote 1: £11,000 / 6035w/ £1.82 per watt (INCLUDES BATTERY)

17x 335 W Monocrystalline Panels (not specified)
1x 6kw inverter (not specified
1x 9.6kwh battery
software etc
scaffolding

Quote 2: £4200 / 2920w/ £1.44 per watt 

Solaris 3Kw inverter
8x JA Solar 365KW Panels
Renusol mounting system
Tigo TS4 Optimisers
Install, Scaffold etc

Quote 3: £6500 / 5400 watt/ £1.20 per watt

15 x Longi Black frame 360W solar panels,
15 x SolarEdge P401 Optimisers.
Mounting equipment for roof installation with cable flashings.

1 x SE 3680 Inverter.
1 x Generation Meter. Connection agreement application & processing.
Scaffolding etc

Cranberryberry

Martyn1981 said:

I'd agree with the comments, for a bungalow a price of about £1/Wp should be doable for say 4-5kWp, and all through a 3.68kW capped inverter.

As you go bigger, the price per Wp should fall. My sister had an install last week of 10.3kWp and that was just under £8.5k (but there was already scaffolding in place).

Wow. I can't get anywhere near those prices! I would jump at 10.3kWp for 9k or so (inc scaffolding quotes I've had)!

Exiled_Tyke

Cranberryberry said:

QrizB said:

I don't know where in the country you are but even at the cheaper end of the scale, £1.26/watt seems a little high. How many quotes have you got? Can you post brief details here?

As a rule of thumb, higher wattage systems should be cheaper per watt, will have better economics and no-one ever complains of having too much solar power.

Do keep in mind that any system capable of producing more than 3.68kW will need prior permission from your DNO and this might include a fee.

I'm in the North West/North Wales border area so we should have lots of suppliers but I've managed to get a few quotes, three of which are (just realised I messed up some numbers in my original post so they don't quite match!).

Quote 1: £11,000 / 6035w/ £1.82 per watt (INCLUDES BATTERY)

17x 335 W Monocrystalline Panels (not specified)
1x 6kw inverter (not specified
1x 9.6kwh battery
software etc
scaffolding

Quote 2: £4200 / 2920w/ £1.44 per watt 

Solaris 3Kw inverter
8x JA Solar 365KW Panels
Renusol mounting system
Tigo TS4 Optimisers
Install, Scaffold etc

Quote 3: £6500 / 5400 watt/ £1.20 per watt

15 x Longi Black frame 360W solar panels,
15 x SolarEdge P401 Optimisers.
Mounting equipment for roof installation with cable flashings.

1 x SE 3680 Inverter.
1 x Generation Meter. Connection agreement application & processing.
Scaffolding etc

If you need optimisers then quote 3 isn't too bad.  If you've no significant shading issues and you've no more than two sections of panels each section having panels all at the same orientation and pitch (as per QrizB's picture above) then really you shouldn't need a SolarEdge system and optimisers.  This would seem to be the case given quote one.    

Martyn1981

Hiya. I can certainly see your frustration, that's quite an eclectic mix of systems.

Do you have a rough idea of many panels can fit on your roof(s)? And will they all have the same orientation?

The Solaredge system concerns me slightly, as it's pushing the kWp to inverter size to the limit, and possibly starting to get wasteful regarding capping. Also, if you don't have shading and are using one roof, then Solaredge may be overkill - but please note, Solaredge is brilliant, I have two systems using it, so if needed, and/or the PV is across two different orientations, then I can understand it.

I think what jumps out at me the most is the difference between a 6kW inverter in one quote, and a 3.68kW inverter in another. It would make a lot more sense to know if you can (hopefully) exceed the 3.68kW cap, or not, otherwise it's hard to judge what might be best.