advice-panels not producing

sheltont

Hi all,

Just wondered if anyone knows about my query.

I've had 4kw system solar pv installed for just over a year, with a sap score of 3380 estimated on the original quote. When the installation certificate was given this showed 3200. The company told me this was an admin thing and not to worry. I got 3211 last year and have complained. No change in story. In addition we haven't saved as much electric as predicted. My wife is a stay at home mum and we've used the panels well but we use far less than national average for electric. We've said this at the quote time and now but been told we should still be achieving £253 saving but we've only got £125.

The company have offered us £250 compensation as a gesture of good will as they say they are within the 10% government tolerance for sap readings so have done nothing wrong.

I worked out we are likely to get £1700 less than was predicted after everything is taken into account in the first 10 years.

I need to know...
Does a sap tolerance exist?
Should I further complain to hies and risk losing the offer?

Thanks in advance.

tunnel

Unfortunately you have fallen for the biggest trick in any installers book. They near enough ALL quote a deemed 50% usage of the generated electric. Average savings from solar are more in line with £80-£120, even I struggle to use 50% with a stay at home wife. The only other way of using more is with the use of a diversion switch for sending any spare electric to heat an immersion tank, only any good if you have one.


As for your generation total, no-one can guarantee the weather unfortunately, if you have better generation than your forecast figures for year 2 are you going to pay the installer some of the £250 back? Thought not!


I would take the £250 and say thank you.

gazapc

What is the exact system size, orientation, pitch and approx location? Is there any any shading on any of the panels? This way we can check your system's performance is reasonable.

sheltont

Hi, the system size is 4kw split evenly on a south/south west split roof so the roof is east west, not ideal I know.

I don't know the pitch but it's fairly steep.

There is no shading, and I'm on wirral, north west.

Thanks everyone for looking into it for me.

tunnel

sheltont wrote: »

Hi, the system size is 4kw split evenly on a south/south west split roof so the roof is east west, not ideal I know.

Care to just expand on that, it's either S/SW or E/W. Slightly confusing?

ed110220

sheltont wrote: »

Hi, the system size is 4kw split evenly on a south/south west split roof so the roof is east west, not ideal I know.

I don't know the pitch but it's fairly steep.

There is no shading, and I'm on wirral, north west.

Thanks everyone for looking into it for me.

Hi, PVGIS (http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php) gives an estimate of 1510 kWh/year from 2kWp in the Wirral facing East (-90 degrees) and 1500 kWh from facing West (90 degrees) so 3010 kWh in total. That's for a roof inclination of 40 degrees, but angle doesn't make a whole lot of difference within the bounds of usual roof pitches.

So that part sounds about right as you've exceeded the PVGIS estimate, which most people seem to do. Obviously generation will vary a little from year to year based on how sunny the weather has been.

Not sure if there's anything you can do about the over optimistic electricity savings, especially since the government uses the 50% export estimate for the export tariff when most people export far more than that.

In my opinion electricity savings shouldn't carry too much weight in the sums as they are hard to predict, unlike the FIT and export tariff which are pretty reliable.

Ed

pw22

I think when we signed our contract a couple of years ago there was something that mentioned that the SAP calculations were an estimate and could vary due to weather etc. I think the method used for producing the SAP figures has changed recently so am not sure if this applies to your install.

sheltont

Thanks folks, looks like most are suggesting the sap readings are accurate, looks like I'll accept their offer them!

Thanks for clarifying it...
Tim

System

sheltont wrote: »

Thanks folks, looks like most are suggesting the sap readings are accurate, looks like I'll accept their offer them!

Thanks for clarifying it...
Tim

I am still slightly confused as the reason why the supplier would have made you an offer at all. My son-in-law lives on the Wirral and has a 4kWp system which, last year, generated in excess of 3600kWhs. My own 2.115kWp system generated1937 kWhs.

Use this link to calculate your own output. Forecast outputs have risen in the last 4 years. My forecast has gone up from 1840 to 1940 kWhs using this tool.

http://re.jrc.ec.europa.eu/pvgis/apps4/pvest.php#

Clearly, this tool isn't clever enough to forecast the weather or solar eclipses!

sheltont

Hi, I've just been concerned that the numbers didn't seem to add up. The installation certificate had 3200kw estimate on it, but our quote said 3380. Is this discrepancy normal? This could be the reason?

Martyn1981

sheltont wrote: »

Hi, I've just been concerned that the numbers didn't seem to add up. The installation certificate had 3200kw estimate on it, but our quote said 3380. Is this discrepancy normal? This could be the reason?

3,380 does seem quite a way from 3,000 that Ed worked out. PVGIS is very accurate, but SAP is a more general number based around Sheffield research, but that said, your gen should be similar to Sheffield.

Perhaps they didn't properly take your orientation into account and based it more on SE and SW rather than E and W.

Your gen of 3,200 (against 3,000) last year is a similar difference to mine, as I got 108% of target last year.

I'd guess that the leccy saving is an estimate, that they 'over suggested', but I'd have thought the annual generation figure should have been more accurate. You could keep arguing with them but £250 is probably about 5 years generation difference (3,000 v's 3,380), so maybe take the money?

Regarding 'normal discrepancy', I'm not sure I can back this up, but my gut feeling is that the SAP figures are usually equal to, or lower than the PVGIS estimates, when folk come on here and ask. So, no, yours doesn't sound right ...... but it's not miles out at +12%. But how do you argue if we get a row of good years, makes defining generation a bit tricky, and a get out clause for installers bad estimates.

Mart.

PS Hello and welcome.