Skip to main content
Observer Ethical awards Winners 2011

YouGen Blog

How much are your solar panels generating?

Posted by Cathy Debenham on 14 February 2011 at 9:39 am

Watching the kWhs clock up as the sun shines is one of the great pleasures of solar PV panels. But which meter do you watch? I watch the total generating meter, and am ashamed to say that I haven't yet worked out what all the different buttons on the inverter do. But that's all about to change...

I've recently got an email from someone else with solar PV panels saying that the figures on his total generation meter are not the same as those on the inverter, and asking whether that's the same for others.

So I'm asking you:

  • Does your inverter give the same measure of total kWhs generated as your total generation meter?
  • If not, which is greater, and how big is the difference?

Answers in the comment section below please.

More information about solar PV from YouGen

Solar PV information page

Inverters for solar PV panels: your questions answered

Is efficiency or cost per watt most important?

Energy companies confuse customers over export meters for feed-in tariff


If you have a question about anything in the above blog, please ask it in the comments section below.

Like this blog? Keep up to date with our free monthly newsletter


12 comments - read them below or add one


aquadesmoComment left on: 8 July 2011 at 10:18 pm

My NEDAP inverter on my 3.8 kWp system gives two separate values: the gross output from the panels, and also the nett output from the inverter. Generally, the output from the inverter is about 8 or 9% less than the raw output from the panels. I say generally because it isn’t always exactly the same from one day to another. The value from the inverter “should” be the same as my OFGEM-approved total generation meter (the gold standard?) but in practice seems to be slightly lower (i.e. more pessimistic) by somewhere between 0.5 and 1%. These conclusions are drawn from comparison of daily readings.

report abuse


rhsComment left on: 20 May 2011 at 2:28 pm

Our production figures compare with those given using the model on

We had lower figures in November through to February, but this was because of shading from a neighbour's tree, which has been removed! Snow and dull days prevented less than one full unit of production on 16 days. Other months have been above estimates. Declared net capacity of 3.85 kW might produce 3200 kWh in a year. To date our best day - 2 May - produced 27 units.  

Answer to original question: 2335 kWh on inverter but 2325 kWh on small production meter in 281 days.

report abuse

Cathy Debenham

Cathy DebenhamComment left on: 16 May 2011 at 10:04 am

Hi Bob, so pleased to hear that you've sorted it out

report abuse


Bob0260Comment left on: 14 May 2011 at 4:16 pm

Inverter shutting down problem is fixed. I contacted the DNO who check the voltage to my house. It was averaging 250 v and peaking at 257 v. The DNO has now reduce the voltage and since then the inverter has been working normally.

report abuse


Bob0260Comment left on: 10 May 2011 at 9:28 am

I have a 3.96 Kw system installed late November 2010. So far it has generated 834 Kw but should be a lot more because I have a problem. My inverter switches off when the sun shines. I am not joking. I sit there watching my meter that shows how much the system is generating. Then about md day the sun can come out from behind a cloud. The watts increase then wam the watts decrease and the inverter is in standby for 3 minutes. on bright sunny days the inverter can be off for 4 to 5 hours during the after noon. It comes out of standby after about 3 minutes. The watts increase and then it realises that the sun is shining and says this is too much like hard work and goes back to sleep for a further 3 minutes.

During April a nearby same size system as mine produced 200 watts more than me.

My installers are useless. They have not got a clue what is going on. 

report abuse


LudgatemanComment left on: 5 May 2011 at 9:08 am

I'd be interested to know what other members are generating from their solar arrays. I have a 3.8Kw system comprising 18 Romag Powerglaz SMt6 units, which according to my MCS certificate have an estimated annual generation figure of 2947Kw.  The system was commissioned in late November, and we have just passed the 1000Kw mark. Daily generation in the current weather is between 15 & 17 Kw, which I'm very pleased with, but how does it compare with other setups of similar size / capacity?

report abuse

Explore Solar

Explore SolarComment left on: 23 March 2011 at 5:55 pm

It is the generation meter that is important, since this is how the payments will be made. The data on some inverters is lost after a power cut. The sunny beam, only stores data for a few months.

report abuse

David Hunt

David Hunt from Comment left on: 17 February 2011 at 10:44 pm

Your Total Generation Meter (usually installed next to your main meter) is ofgem approved and calibrated to be exceptionally accurate. Though they do usually clock up a very small amount of use in calibration, usually under 1kwh. The Sunnybeam, and inverter display are not as tightly calibrated so there can be differences. As long as they are not huge you should be ok. But if substantial it's worth contacting your installer. But the Total Generation Meter is the most accurate, and the one on which your feed in tariff payments are made.

report abuse

Paul Hutchens

Paul Hutchens from Eco2SolarComment left on: 16 February 2011 at 5:14 pm

There is usually a difference as the meter starts with a figure of about 0.7kWh (not sure why - maybe they are tested before we get them). So the meter is generally slightly higher than the inverter - but the meter is used for claiming Feed in Tariffs - 0.7kWh free with every system!

report abuse

Cathy Debenham

Cathy DebenhamComment left on: 15 February 2011 at 9:02 am

Yes, it's the small meter - that's the one you read to claim your feed-in tariff.

report abuse

ian day

ian dayComment left on: 14 February 2011 at 6:37 pm

What is a total generation meter ? I have a meter on the inverter and another small meter (a Sunny beam) - is this variance you refer to ?

report abuse


Fred1Comment left on: 14 February 2011 at 3:47 pm

the cumulative from my Invertor and from my total generation meter track almost exactly.I have generated over 3000kwh and the difference is less than one kw.

report abuse

Leave a comment

You must log in to make a comment. If you haven't already registered, please sign up as a company or an individual, then come back and have your say.