PV Panels

[Graham Smith]

We had a 20 panel 3.9Kw system installed on 24th February 2012 just before the good rate ended and the estimated generation on our certificate is 2900Kwh.

To date (just 7.5 weeks later), we've generated 700Kwh.

Now, I know we've had some great weather lately, but what happens when I generate more than the 2900Kwh that's on the certificate?

Are they likely to come round and want to read my meter every quarter, or is this sort of thing quite common?

A friend of mine who has had solar panels installed for quite some time suggested that these estimate figures are just that - 'estimates' and can sometimes be wildy inaccurate.

I would appreciate any advice or reassurance anyone can give me.

Finally - if I generate over the estimation - will they make me payback the excess? - hopefully not!

 

[SpitfireW'sale]

We had a 20 panel 3.9Kw system installed on 24th February 2012 just before the good rate ended and the estimated generation on our certificate is 2900Kwh.

To date (just 7.5 weeks later), we've generated 700Kwh.

Now, I know we've had some great weather lately, but what happens when I generate more than the 2900Kwh that's on the certificate?

Are they likely to come round and want to read my meter every quarter, or is this sort of thing quite common?

A friend of mine who has had solar panels installed for quite some time suggested that these estimate figures are just that - 'estimates' and can sometimes be wildy inaccurate.

I would appreciate any advice or reassurance anyone can give me.

Finally - if I generate over the estimation - will they make me payback the excess? - hopefully not!

It's quite common for an install to produce significantly more than the SAP calc, which is a relatively inaccurate guide that does not take several factors into consideration. It is also fairly common for panels to produce very well in their first few weeks of use.

Your friend is correct, estimates are just that, and solar performance is very difficult to predict with accuracy.

You are very unlikely to be investigated and you will not have to pay back excess. Be glad you have a good system installed.

It will be interesting to see what happens for any systems that are wildly over producing, as there are bound to be some less moral folk who bolster their generation tariffs with generators, illegal wiring etc.

 

[Graham Smith]

But would 700Kwh in just 7.5 weeks seem excessive?

What's the highest sort of generation a house with a 3.9kwh system installed, south facing be expected to produce over the course of a year (or even a day)?

 

[Scobo]

We have a 2.88kw system and it's made about 360kwh in the last 6 weeks.
Bearing in mind, we're in Scotland and March was an exceptional month weather wise.
Take a look at pvoutput.org and you'll see a whole range of systems listed and the outputs they've generated since installation.
You can search by system size to compare with yours.

 

[FB.]

The SAP targets set for most solar arrays seem to err on the side of caution. The reality seems to be 10% outperformance or more.

If someone consistently generates large amounts of solar electricity, they may be asked to allow someone to come into their house and read their generation meter.
If you've done nothing wrong, you have nothing to fear.
The inverter's logs should roughly correlate with your generation meter. I can look up generation stats from any past time period by inputting the time/date range.

My inverter's "lifetime" generation statistics are in close agreement with my generation meter. The difference is 0.5% (i.e. the generation meter is showing 99.5% of the amount shown in the inverter's logs).
The 0.5% discrepancy may be due to minor calibration errors or minor losses due to the cable from the inverter to the generation meter.

But since my inverter and generation meter are 99.5% in agreement, I can cast "reasonable doubt" on anyone claiming that I have acted illegally in the 17% above-target generation stats which I've attained.

Also bear in mind that many places have seen remarkably good weather in recent weeks.

In the same period as you, I have generated about 525kWh from a 3.75kWp system facing a little to the East of SouthEast.
If I had 3.9kWp, my generation would have been 550kWh.
I would expect a South-facing system to generate about 10% more than mine in the same period (about 600-625kWh).

And, to be honest, here in the East, the weather has been much cloudier than most other parts of the UK, and in my area there's been more rain than usual and we don't have a drought.

So I can quite believe that many people with 4kWp systems could be exceeding 700kWh since late February.

 

[Gavin A]

If you generate more than predicted DECC's crack PV police commando unit will hit you with dawn raids and take away your first born as human sacrifices to the god of the DECC spending envelope.

harsh but fair.

 

[Glen Powell]

If you generate more than predicted DECC's crack PV police commando unit will hit you with dawn raids and take away your first born as human sacrifices to the god of the DECC spending envelope.

harsh but fair.

I had that happen to me, I asked them to take the wife instead, they looked and took pity on me and left my first born, however the wife is still here

 

[SRE]

We'll do it - expenses paid of course :sunny: