Being a PV Generator: Lessons I Have Learnt Part 1

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It’s now been over 2 months since my solar panels were installed and commissioned.  And I have just filled in my first generation form to receive my first FIT payment.  I have also learnt a few new things about PV generation that I thought it would be useful to pass on to others.

Lesson #1 – your electricity usage meter should not go backwards!

In an earlier blog I wrote excitedly about the thrill of my electricity meter going backwards. Well, my first big lesson is that it should not be running backwards!  Basically, as I am quite a frugal electricity user anyway my generating capacity over the summer (I use the term lightly) months has slightly exceeded my usage.  And, because I have an ancient, analogue electricity meter recording my general usage, I was finding that it was running backwards and actually giving me a negative reading.  This put me in the unusual position of giving my energy supplier a negative reading for my quarterly bill update – a case of them paying me for my (non)usage.

Therein lies a problem with old analogue meters, they do not simply stop moving when you add a micro-generator to the circuit that is supplying you with all the electricity you require, they will turn backwards, recording the total amount of generated power you are producing – regardless of whether you use it, or whether it goes back to the grid.

I’ve informed my electricity supplier of this and they are now arranging for me to get a new digital meter; which will simply stop moving forward when I am using my own generating power, but will never turn backwards.  These are called ‘back stop’ usage meters apparently

I did ask whether it would be possible to bypass the installation of another ‘dumb’ meter and go straight for a smart meter, given that my meter will have to be changed again within the next 8 years to comply with the timetable for all homes to have smart metering by 2019, but unfortunately, as I’m not with British Gas, this is not an option currently – which seems a wasted opportunity to me.

So my earlier excitement of the possibility of receiving a 6pence electricity bill was short-lived I’m afraid.  I’m not sure how we will work out exactly how much electricity I have actually taken from the grid in the last 2 months – as opposed to my self-generated usage, but I’m guessing it is going to be a lot higher than a few pennies worth.

Related blog posts:

Being a PV generator: Lesson learnt Part 2

PV systems and meters running backwards: need for clear guidance



4 comments… add one
  • john sharp September 17, 2011, 9:58 am

    Hello Paula, interesting comments you have raised. My background is Electrical Power on Aircraft and I have also installed PV at my home. I asked EDF if they can supply a device which would show me when I am running on Solar and when I am importing from the Grid. This would allow me to switch various appliances in order to optimise my electricity costs. No simple, cheap devices are available from them and so far I havn't found a commercially available one to purchase (still looking). Maybe there is a market opportunity, most people with PV would like to know when their domestic needs are being met entirely from their PV system. I am trying to devise a cost effective solution which would fulfill this objective. Have you found any product already on the market? Kind Regards, Johnny

    • Paula September 17, 2011, 10:33 am

      Hello Jonny
      Thank you for your comment. I don’t have a device exactly as you describe, but what I was given as part of the installation is a solar Wattson. Basically it is a ‘real time display’ meter but it also monitors my generation. It tells me how much I am using; how much i am generating and it gives me my ‘net usage’ So basically, when I am generating more than I’m using it will display a negative number – which I love to see!

      I use the Wattson to figure out when to put the washing machine and dishwasher on. I guess it does’nt tell me generally, over a time period, what the split of generated versus consumed is, but its a good start. I can also download all the data of consumption and generation from its memory and produce graphs that show both lines, which is also useful.

      The only problem with the Wattson device is that it isnt the cheapest RTD on the market, I think this solar Wattson retails at about £150

  • kcod May 14, 2012, 2:18 pm

    When I evaluated whether to install a PV System I beleived that (effectively) the meter WOULD go backwards and that I would henceforth only pay for my Net power consumption (averaged over the year).  It was on this basis that I bought the system.
    When E.ON sent me the Contract to sign they asked me to read it 'very carefully';  this I did, and noticed some errors and ommisions.  I told E.ON about these and it was agreed that I should write some corrections and additions in a letter that would form an addendum to the Contract.  Amongst the additions (because the export power was to be 'assumed' to be 50% of the generated power and not because I thought there was anything wrong with the meter) I added a clause that "the current meter type shall be retained".
    Thus, I find myself in the position where I have a Net usage meter that shall be retained.
    However, when E.ON noticed that the meter was going backwards they attempted to claim that I had 'tampered' with it and that it must be changed for one of a different type.  Then they claimed that the meter had developed a fault and that it must be changed for one of a different type.  Niether of these claims is true;  the meter is simply designed to be a very accurate Net usage meter (that shall be retained).
    I have asked multiple times for E.ON to provide me with the Contractual basis (even in the absence of my additional clause) that states that the meter must be an import-only meter and not a Net usage meter;  this they refuse to do but they continue to bludgeon me with vastly over-estimated "estimated" bills.
    Quite honestly I am shocked that E.ON are unable to provide me with whatever clause it is that states that the basis of the User Contract is for imported power only and not for Net usage – surely this must exist somewhere?  Or maybe it just doesn't.
    The truth is that the Electricity Generators are trying to pull a very clever trick in forcing people (with no Contractual basis) to pay for their import-only usage and not for their Net usage.


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