Solar Panel Quote

frozen_wastes

After years of saying I'll get a solar panel array, I finally went out and requested a few quotes, and now my first quote came back from a local MCS registered electrician.
£10k.   For that I get:
8.9KWp solar array with JA Solar 320W Panels, with SolarEdge optimisers built in.
10KW HD Wave SolarEdge Inverter.
GSE Adaptors allowing for an "in-roof" solar installation.
Export limiting device, if required by the DNO.
All labour, and access equipment including G99 DNO application.
Overall that works out as being £1.12/WattP which I think is reasonable.
I also got an "on-roof" quote from the same electrician.  This came out to be £800 more expensive.  His reasoning:  Mounting the brackets to the counter battens, getting the tiles cut and profiled around the brackets, and flashings all cost a lot more labour.  The GSE system is simpler in terms of cutting tiles and flashings.

So why 8.9KWp?  It's a lot, compared with historical domestic solar installs:
The estimated output is reckoned to be 7.1MWH in the first year, and then declining 1%/year thereafter.
My existing electricity consuming is about 2.7MWH/year (increased from 2.3MWH/year on account of working from home).   On account of nighttime consumption, I'll probably only save about 50% off my annual bill.

So on the face of it, the system is massively overspecced based on *existing* consumption.  So in order to make this worthwhile, I'm looking at *future* consumption.
1.  Straight off the bat, I can timeshift my washing machine and dishwasher to run during the daytime, so that means the only heavy loads during the evening time are the grill/oven and the vacuum cleaner.  That will maximise my use of solar power.
2.  Second,  I'm going to get a hotwater load controller (either SolarEdge or My Energi Eddi).  That's worth about 4KWh/day off my propane bill. (maybe £70 per year).  

So far, this is just minor tweaks relatively speaking.  But let's look at the numbers.
Let's assume I save 50% off my electricity bill: £210/year (1350KWh)
And I save £70/year off my propane bill (1168KWh)
That leaves the remainder for export (assuming no export limitation is stipulated):  4589KWH @ 5.2p/kWH.  £238/year
Added all up thats a £518/year saving, just under 20 year payback.  On the face of it:  Only marginally worth it, especially considering that the SEG price could disappear or power export limitations could be imposed.
But the numbers fail to consider electricity price inflation.  Once that's brought in (let's assume 6%PA), then the payback is shorter (13 years according to my quote).
But these minor tweaks fail to consider the real reason for "going large".  The other thing is that the electricity production estimate in the quote has been an underestimate for other people in my general location, so I'm likely to produce more electricity.

3.  Third.  Electric Car.  Not this year, but very likely next year.  This is the big reason to go big with solar power.  15000 miles / year @ 3 miles / kwH = 5000kwH/year.  Assuming 80% of miles are provided at home, then there's 4000kwH/year up for grabs.  Assuming half of that is provided by the solar power, and the rest is provided from the grid: £320/year saving.
Adding that up to the previous savings without inflation taken into account: £838/year saving off my electricity bill.  So we're now looking at a 12 year payback, and once inflation is considered, it's probably down to 8/9 years payback.
Now if I can use my car for vehicle to grid functions, then savings become even higher.  Right now though, It's either ChaDeMo, or it's wait for Type 2 specifications to evolve.

4.  Fourth, 7 years in the future, my propane tank will be life expired and due for replacement (a full dig it out of the ground job).  Before this stage, I'm wanting to prepare my house for electric heat pumps.

Petriix

Sounds reasonable. I would hope you could get under £1 per kWp at that scale but it depends on your area and specification.

With tanked gas you can probably justify the hot water diverter if you've got the right plumbing in place already, but you will lose your SEG payments for each kWh you divert rather than export so need to factor that in to your calculations.

With the EV it's really dependant on how often it's parked at home during the day. Also, with time of use tariffs (like Octopus Agile) you might earn more by exporting than you save by diverting to the car when compared to the cheaper overnight charging. The sums are more complicated but worth doing.

frozen_wastes

With the EV it's really dependant on how often it's parked at home during the day. Also, with time of use tariffs (like Octopus Agile) you might earn more by exporting than you save by diverting to the car when compared to the cheaper overnight charging. The sums are more complicated but worth doing.

I've seen the Octopus Go Tariff (Agile Tariff is even more complex) with 5p/KWh between midnight and 4am.  You are right.  I could charge a car up in the cheap period (28.4KWh EV + 4KWh HW + washing machine/dishwasher), and then export the solar power at 5.2p/KWH during the day and that would be more economic. 

That tariff actually changes the equation away from making solar panels worthwhile, as it essentially means that a much smaller fraction of the generated electricity is consumed on site.  Essentially the economics of solar panels have to be based on export prices and daytime electric consumption.  Now at 5.5p/KWh, it would take just over 25 years for the solar panels to payback, assuming no inflation and no electricity consumed on site.  It's right on the margin of being worthwhile.  Now of course I haven't considered daytime consumption into that figure, which would reduce the payback period.

Now 25 years is a very long time, and the electricity market will likely change a great deal in that time.  Chances are that the SEG price will become dynamic: Very Low / Zero during a sunny summers day, and very high during a cold still winters night.  That works against solar panel economics even more, but it would strongly favour battery storage.  Trouble is, battery storage is very expensive right now and the existing buy/sell price difference in electricity price is so small that any advantage would be lost to the storage cycle inefficiency of the battery.

DiggerUK

It seems your calculations expect to get the plated value of electricity for the entire 25 years. The efficiency of your panels, at best, will be 20% from new and reducing over time.

No calculations have been made to cover maintenance and repairs. For instance, replacing your inverter would cost over £1k+, excluding labour and vat. You could take out monthly insurance for around £15 pm, which is £4,500 over 25 years for parts and labour.

All in all it doesn't seem much of a moneysaving exercise, which is what this site is all about..._

frozen_wastes

DiggerUK said:

No calculations have been made to cover maintenance and repairs. For instance, replacing your inverter would cost over £1k+, excluding labour and vat. You could take out monthly insurance for around £15 pm, which is £4,500 over 25 years for parts and labour.

That's a very poor value insurance deal.
The inverter has a 12 year product warranty (extendable to 25 years for a fee). The fact that SolarEdge offer a warranty extension upto 25 years is enough confidence that these items, which are solid state, will actually last the full 25 year lifetime (and probably longer).  In 12 years time, if the worst happened, there's no doubt that power electronics will have evolved in terms of product price reductions. If fact it wouldn't suprise me if they follow similar price trends to microelectronics.

Optimisers and panels both have a 25 year product warranty.  With warranties like that, there's no basis for an insurance product like the one that you describe.

DiggerUK

Warranties only cover replacement parts, not labour costs. What calculations regarding reduced output have you factored in..._

ABrass

frozen_wastes said:

DiggerUK said:

No calculations have been made to cover maintenance and repairs. For instance, replacing your inverter would cost over £1k+, excluding labour and vat. You could take out monthly insurance for around £15 pm, which is £4,500 over 25 years for parts and labour.

That's a very poor value insurance deal.
The inverter has a 12 year product warranty (extendable to 25 years for a fee). The fact that SolarEdge offer a warranty extension upto 25 years is enough confidence that these items, which are solid state, will actually last the full 25 year lifetime (and probably longer).  In 12 years time, if the worst happened, there's no doubt that power electronics will have evolved in terms of product price reductions. If fact it wouldn't suprise me if they follow similar price trends to microelectronics.

Optimisers and panels both have a 25 year product warranty.  With warranties like that, there's no basis for an insurance product like the one that you describe.

It's an insanely bad deal. 4,500 is three full inverter replacements, even leaving a large margin for fitting costs.

Do you have any shading? Solar edge is only useful if you're getting some shade on panels and you don't want to lose the entire string.

Martyn1981

DiggerUK said:

It seems your calculations expect to get the plated value of electricity for the entire 25 years. The efficiency of your panels, at best, will be 20% from new and reducing over time.

No calculations have been made to cover maintenance and repairs. For instance, replacing your inverter would cost over £1k+, excluding labour and vat. You could take out monthly insurance for around £15 pm, which is £4,500 over 25 years for parts and labour.

All in all it doesn't seem much of a moneysaving exercise, which is what this site is all about..._

That's very poor advice.
Firstly I'd be interested to know where you are getting your panel degradation info from. Mine are nearly 10yrs old and performing as new. The most detailed report I have seen suggested an approx 0.4% loss per year for post 2000 silicon panels, and of course panels have gotten much better over the last 20yrs. So at worst we have 25yrs x 0.4% = 10%, v's your 'at best' figure of 20%.

Next we have your claims about maintenance and repairs, and an insane £4,500 insurance suggestion. The inverter (as stated) is a SolarEdge HD wave model. These are extremely reliable (I have one HD and one older 'normal' one), come standard with 12yr warranty, and this can be increased to 20yrs for little over a £100 so is typically thrown in by the installer.

Then you state the warranty only covers parts, not labour, which again is untrue - I had a PO replaced on the roof for no cost when it failed.

Martyn1981

To the PO, I think your inclusion of a BEV or BEV's is spot on. In fact if the household ends up with more than one, then simply noting the weather forecast and leaving the least charged BEV at home, will allow for nearly 100% solar charging during the best 6 months of the year. We have a much smaller PV system but have managed to charge the BEV's almost exclusively from solar since April.

ed110220

Martyn1981 said:

DiggerUK said:

It seems your calculations expect to get the plated value of electricity for the entire 25 years. The efficiency of your panels, at best, will be 20% from new and reducing over time.

No calculations have been made to cover maintenance and repairs. For instance, replacing your inverter would cost over £1k+, excluding labour and vat. You could take out monthly insurance for around £15 pm, which is £4,500 over 25 years for parts and labour.

All in all it doesn't seem much of a moneysaving exercise, which is what this site is all about..._

That's very poor advice.
Firstly I'd be interested to know where you are getting your panel degradation info from. Mine are nearly 10yrs old and performing as new. The most detailed report I have seen suggested an approx 0.4% loss per year for post 2000 silicon panels, and of course panels have gotten much better over the last 20yrs. So at worst we have 25yrs x 0.4% = 10%, v's your 'at best' figure of 20%.

Next we have your claims about maintenance and repairs, and an insane £4,500 insurance suggestion. The inverter (as stated) is a SolarEdge HD wave model. These are extremely reliable (I have one HD and one older 'normal' one), come standard with 12yr warranty, and this can be increased to 20yrs for little over a £100 so is typically thrown in by the installer.

Then you state the warranty only covers parts, not labour, which again is untrue - I had a PO replaced on the roof for no cost when it failed.

I think he's got confused by the efficiency of solar modules, where 20% would be a good but not best panel. Not that this has any relevance to these calculations as 7.1 MWh/year from 8.9 kW of panels is in the right ballpark. Depends where you are in the country but in the south and facing south you should get ~1000 kWh per kW per year so 7.1 MWh certainly isn't excessive. 
I used https://re.jrc.ec.europa.eu/pvg_tools/en/tools.html to estimate output.

frozen_wastes

Martyn1981 said:

To the PO, I think your inclusion of a BEV or BEV's is spot on. In fact if the household ends up with more than one, then simply noting the weather forecast and leaving the least charged BEV at home, will allow for nearly 100% solar charging during the best 6 months of the year. We have a much smaller PV system but have managed to charge the BEV's almost exclusively from solar since April.

Essentially now, the only thing I'm waiting for now is a formal letter from my building standards department saying I can go ahead without a building warrant.  I know these things aren't normally needed, but the "in-roof" nature of the solar panel array might change the equation a little.  We shall see....

I'm also told that it's likely that a G99 DNO application is likely to be accepted without any export limitation being stipulated.  That will be a very good thing.  Part of my thinking is that as solar panels get installed on more properties, then the DNO is more likely to say that due to network constraints they have to limit export.  So if I "get in now before it's too late", then I have an advantage.

I have to say that I'll be very excited to join the Solar Club.  It's the first step of many things to come in the future!