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Is all my solar electricity being exported?

Posted by Chris Rudge on 10 October 2013 at 9:22 am

Q: I suspect that all the generation from my 3.12 kW Solar photovoltaic panels is being exported as since installation almost 2 years ago my electricity bills have increased rather than reduced despite over 5,000 kWh being generated. How can I check this is the case?

A: Any power being generated by your PV system will be available for use in the premises 'at the point of generation'. This means the generated power is only available as it is being generated, otherwise it is exported. The fact that your generation meter has clocked up over 5,000kWh shows the system is sending power somewhere.

There are a couple of instances in which the power will seem not to be available due to installer error:

1) If somehow the installer has connected the PV onto the wrong side of the import meter, your bills would be unaffected though you would still be using the generated power. In theory this should not occur due to meter seals, etc but we have seen some underhand practices simply to make wiring easy for the installer. One scenario that we've seen is using the outside Meter Box to house the PV mains interface.  

2) The installer has connected the PV onto another supply. For example the flat downstairs, etc. This could occur in a multi occupancy building quite easily.

Another aspect to think about is whether you have installed additional electrical devices in the house since the PV installation.

Or is could simply be, that like most other electricity companies, your supplier has been turning up the unit costs over the last few years. Certainly, a couple of years ago I was on 12p a unit. Now I'm on nearer 15p a unit with a larger standing charge too!

Note from Editor: In addition to what Chris has said, I'd like to add a bit about how active you are in using solar generated electricity. There is often an assumption that because the assumed export for the purposes of the feed-in tariff is 50%, that most people will use the other 50% at home. However, my impression is that this won't be the case for most people. We have a much smaller PV system than you (2.1kWp), and I work at home, and we try to put washing machine and dishwasher on when the sun is shining, yet we only use 35% of the electricity we generate. If you are out during the day, and don't put appliances on to run during daylight hours, then you will use less.

More information on solar PV and meters on YouGen

YouGen guide to solar PV

How do I get the best out of my solar panels?

How to use excess solar-generated electricity to heat water

Photo Credit: dibytes via Compfight cc  

About the author: Chris Rudge is a qualified electrician who specialises in renewable energy.

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

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Comments

18 comments - read them below or add one

Ian Dickson

Ian DicksonComment left on: 16 September 2015 at 5:31 pm

Is there a simple way, preferably wireless and with an app, to actually measure what proportion of your PV solar electric is being diverted back to the grid? If there isn't a blog article on this could one be opened?

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paul53

paul53Comment left on: 11 February 2015 at 8:31 pm

 christine  if  they are  connected  to one  meter you  should be getting  the free  electricity remember  today  was  very  dull we only  got ten  pence worth of power .wait till the  suns bright and  then  check .

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Christine B

Christine BComment left on: 11 February 2015 at 12:17 am

We have just had solar panels fitted.  We have one electric meter which serves the house and extension.  With two fuse boxes one for main house and one for extension.  The panels have been wired into the extension fuse box.  Will any of the power come through to the main house or will it only power extension.  Sorry may seem silly but i don't understand if power flows both ways.

My meter is still wizzing round just as fast during the day as it does in the evening when the solar isn't working.  I  tested with exactly same things working.

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Cathy Debenham

Cathy DebenhamComment left on: 6 January 2014 at 9:50 am

@eiflon I have heard of an energy company charging in a situation like this, so I echo Chris's advice that it's a good idea to tell them as soon as possible, and keep the proof.

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Rudge Energy

Rudge EnergyComment left on: 5 January 2014 at 9:20 pm

eifion.. Having your meter run backwards is quite common if you are fitted with an older 'spinning wheel' meter.

Some of the more recent wheel meters are fitted with a rachet to stop this occurring, most that we have found fitted do indeed run backwards when your solar PV system is generating more electricity than your house is using.

It does not take too much thought to realise that running your meter backwards will mean obtaining free electricity, as you are already paid for generating power (FiT's), and an additional payment for export. This is outside the contract you will have with your electricity supplier, and if you've not done so already, it will be best to contact them and let them know of the situation.

As many electricity supply companies have changed hands over the years, plus if you are someone that hops around suppliers depending on electricity prices, records of quite what type of meter you have fitted will have faded into obscurity. 

Though I have never heard of a case, your electricity company would be entitled to estimate the amount of power you've had for free and add this to your bill. Over a few years, the running total can accumulate and without you keeping precise records, you'd be hard pushed to argue otherwise.

On the other hand, we have a number of customers who have reported these meters to their suppliers a number of times, (and recorded this), and still are enjoying the benefits of free electricity. As long as you can prove you have informed your electricity company (email or letter), then you should be safe from future restrospective claims if they occur.

As Smart meters are due to be installed in 5-7 years (but dont hold your breath!), power companies may simply be saving manpower knowing the impending Smart meter will completely resolve the issue.

 

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eifion

eifionComment left on: 29 December 2013 at 2:52 am

Having only very recently installed solar I have noticed that my meter does run backwards when the power generated is at its most during bright weather. i suspect the meter is old but whos responsibility is it ?

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James@Joju

James@JojuComment left on: 12 November 2013 at 1:27 pm

Richy, do you recall what make/model of meter it was ?

 

To be fair in the installer it's not easy to test if you aren't actually exporting at the time, especially if the meter only reads whole kWh like some.

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Richy_White

Richy_WhiteComment left on: 30 October 2013 at 10:16 am

Our PV's were in stalled in December 2010 After 3 winter months we realised our EON 'outside' meter (that was only 10 years old)  was adding what we were using to what we were generating - it was a fualty meter - nobody had bothered to check it during the installation.   Took us a year of emails and calls to get £20 back from EON as we had overpaid for our electricity.   Problem wasn't noticed in winter - it's only when April 2011 came around that we noticed what was happening.   Get your supplier to check the meter ASAP.

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MuppetKeeper

MuppetKeeperComment left on: 23 October 2013 at 2:19 pm

Thank you James, I contacted my installer 10 days ago, they seem less than bothered, despite me sending them loads of data / chasing emails.  I may have to pop over the the rate my installer link soon :)

 

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James@Joju

James@JojuComment left on: 21 October 2013 at 2:56 pm

Muppettkeeper- You can check if the solar is wired the correct side of the utility meter (ie your side) by checking that the meter stops advancing when you are exporting ie when you know you are generating more than you are using. You should also get a constant red or green light on the utility meter at that time. (if its old it might go backwards but that's another story...!)

It's more likely that just one of the owl clamps is wrong/not plugged in fully The fact that the utility meter agrees with the owl consumption suggests you are using the method with 2 clamps, not 3 ? See here -

http://www.theowl.com/products/intuitionpv.php

If so try plugging the clamp in again. Does the owl agree with the inverter ?

maybe this discussion is getting a bit detailed...probably you should call owl/your installer first :)

 

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MuppetKeeper

MuppetKeeperComment left on: 19 October 2013 at 4:04 pm

@James,  I initially thought my clamps were the wrong way around, but the utility meter and generation meter seem to agree with the OWL. (Within a few percent).

Theoretically, is it possible that miswiring the PV installation could be pushing the solar generation through the utility meter circuit?  I would have thought that unlikely, as I did use a well known company for my installation.  (I'm not going to name them as if it's me not understanding something, I don't want to give them a bad name.)

MK

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Cathy Debenham

Cathy DebenhamComment left on: 18 October 2013 at 10:09 am

Hi James. I've asked both of them. Will post here if I get an answer.

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James@Joju

James@JojuComment left on: 16 October 2013 at 1:13 pm

It could be that the current clamp is on the wrong way round (as with the Wattson equivalent you need to get it the right way.)

The Eco-Eye can also be used for 'rough' export metering as it senses direction.

If you want to combine it with the generation meter so that you can check historic consumption/generation data etc on line we supply a system that will do that, and provide underperformance alerts (taking account of weather).

 

I would be interested to know from Dave/Tom which meters read export as import ! (other than simple clamp meters, as mentioned above.)

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MuppetKeeper

MuppetKeeperComment left on: 15 October 2013 at 5:54 pm

I suspect I will be the same, exporting almost all of my generation. I have a 4KW installation, and everything in my house is energy efficient and no one home during the day.

I'm looking at installing a system to heat my water with real time load management, the initial cost of £400 should be covered in a few years.

I have an OWL Intuition PV system, which should measure generation / demand / export, but there is either something wrong with it or the installer messed up its set up. Once I have that sorted I will have data to make a decision.

 

MK

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Cathy Debenham

Cathy DebenhamComment left on: 15 October 2013 at 11:23 am

Good question @aquadesmo. The installer I used (Abacus Renewable Energy) did - and it added about £45 to the cost of installation. So I know that I export around 60% of my electricity even though I work from home, actively manage when we do the washing, hoovering etc so that it coincides with sunshine. We only have a 2.1kWp array, so those with a 4kWp probably export more.

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aquadesmo

aquadesmoComment left on: 14 October 2013 at 8:47 pm

Because we are deemed to export 50% of what we produce, and because it is not cost effective to install and pay for "maintenance" of an official export meter, most of us don't actually know what proportion of our generation is exported.  Why do installers not routinely offer the (very cheap) option of installing an extra meter  to measure export (without registering it) simply to allow the end user to really understand what is happening with their generation?  (Because of my curiosity about my own system, I recently got my electrician to retro-fit one to my set up.)

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Cathy Debenham

Cathy DebenhamComment left on: 11 October 2013 at 8:17 am

Two comments on this from Twitter yesterday:

Dave Jones ‏@davejones7923h

@YouGenUK some meters incorrectly measure export as import, thus meter goes up when exporting. Simple to test when sunny!

 

Tom Huxley ‏@TheTomHuxley23h

@YouGenUK A useful addition to that article would be to point out that *some* meters read export as import - thus giving false readings.

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GreenGenUK Limited

GreenGenUK LimitedComment left on: 10 October 2013 at 3:39 pm

One other thing to consider is some home owners beleive its best to use all of their appliances during the day after they have had Solar PV fitted. This is partially correct but dependant upon a number of things:

- Is the sun shining
- What does the appliance require to run and how long will it be on
- Do you have an Off peak tariff? If so you will be paying more during the day than at night. if this is the case its vital that the power coming from the pv is more than the amount you will pull from the grid if you turn on an appliance as your day time rate could be 3 times as much as your night rate.

Its that classic line every installer hears on their way out of a recent install, "so love, you will have to do all your washing and cooking during the day now!"

Just my two pennys
Rob
GreenGenUK

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