PV Monitors

John_Pead

Hi

Last year we entered into a deal with a solar power company whereby they had a 20 year lease of our roof and installed solar panels and we could draw off up to a certain amount of power whilst the panels were generating and the residue was fed to the grid so providing income to the company. We were promised 37% average savings on our electric consmuption but do not seem to be getting them. In fact our consumtion 2015-6 is greater than 2014-5. The system uses a Emlite meter but, according to Emlite, this only gives generation figures. The solar company can only give these figures too. Now I am a suspicious bod who would like proof that we are actually drawing off electricity daily from these panels for house consumption. Can anyone suggest, from experience, a good monitor which can be easily fitted, to monitor the power produced by the panels, the energy exported to the house usage, and the residue fed to the grid. It would be helpful if this was something a layman could use (like me!) and which would feed by wifi to a computer system ( I have an iMac ).
many thanks
John

Cardew

Welcome to the forum.


You have what is referred to as a Rent-A-Roof(RAR) system.


I believe you have slightly misunderstood the system. The RAR company gets the subsidy for ALL electricity generated by the panels regardless of that electricity being exported to the National Grid or used in your house. i.e. If the panels generated, say, 3,000kWh pa it wouldn't matter to the company if you only used 1kWh or the whole 3,000kWh.


The talk of 37% average savings indicates the firm is 'A Shade Greener'?? If so I don't think you were 'promised' 37% savings - merely that is the reported average saving of their customers.


How much electricity you do use 'in house' is up to you, and if you read the many posts from PV owners on this forum you will see it is very difficult maximise your usage of the Generated electricity. You need to have appliances ready to switch on when the generation is at maximum. The important point is to appreciate that you are not restricted to the amount of PV generated electricity you use, but in practice it is difficult to maximise the amount.


The initial estimates were that with a largish PV system the savings might be in the region of £50 to £100 a year. If you have a Hot Water tank(and not a Combi) you can use a device like an Immersun to divert excess electricity to the immersion heater of that tank.

ajbell

Had mine installed last November.
Used to use 3200kwh per year.
Now averaging 2-3 kwh per day so less than 1000 kwh per year.
I do have an iboost and a hatred of exporting though.

Martyn1981

John_Pead wrote: »

We were promised 37% average savings on our electric consmuption but do not seem to be getting them. In fact our consumtion 2015-6 is greater than 2014-5.

John

Hiya John, welcome to the forum. That sounds odd.

Firstly, savings are hard to define, but with no effort, just baseload savings you should really get £80, so £120+ isn't unreasonable. So it is odd you haven't seen a reduction.

Need to be careful on numbers too, in my case import has gone down nearly 50% (from 3,000kWh to 1,600kWh), but the bill hasn't dropped as much since the standing charge throws that out. Lastly, the 1,400kWh I used represents only about 30% of generation, so we have import, bill and consumption percentages, which all tend to get bandied about, but can differ significantly.

When you say consumption has gone up, I assume you mean import, as consumption is very hard to guess now without a measure of export (as well as PV generation).

If your import has actually gone up, then something sounds wrong. Can you think of a reason why your consumption may have gone up considerably? If not then you need to investigate further. How much are we talking, what are the pre and post PV leccy bill units?

Some domestic meters can actually add export on as import. It's an anti-tamper setting, but very rare, tends to be on Siemens meters, so check the make of your domestic import meter, the one that is used to calculate your leccy bill.

There's more on the subject here in section 4a of the PV FAQs.

Mart.

John_Pead

Thank you all for your comments. The company's literature definitely promised a saving in electricity used. I have carried out a survey of our electricity usage over the last two years and it has definitely NOT gone down. We do use most heavy electric user appliances during sunlight hours and not at the same time.
I have read that there are monitors which can be literally clipped to the wires of the pv meter which will show the breakdown of 1. production, 2. House usage and 3 electricity exported to the grid. Have any of you got one of these and if so which and what is your experience with it. I am very surprised that the Emlite meter does not show such information but, there you go, technology is not always what you want.

legoman62

John_Pead wrote: »

Thank you all for your comments. The company's literature definitely promised a saving in electricity used. I have carried out a survey of our electricity usage over the last two years and it has definitely NOT gone down. We do use most heavy electric user appliances during sunlight hours and not at the same time.
I have read that there are monitors which can be literally clipped to the wires of the pv meter which will show the breakdown of 1. production, 2. House usage and 3 electricity exported to the grid. Have any of you got one of these and if so which and what is your experience with it. I am very surprised that the Emlite meter does not show such information but, there you go, technology is not always what you want.

Like others on here, I've got a Wattson Solar plus which will do that you want.

Very easy to fit. and gives reasonably accurate readings

I also have an energyhive hub which works with Wattson.

What type of inverter do you have. I have a SMA inverter, and can moniter output through Sunny Explorer:D

ajbell

It also helps if you change your usage.
For example boil the kettle during a sunny spell and maybe put it in a flask.
I charge all my laptops and tablets/phones during the day and use them on battery at night.
It's up to you to take advantage of it.

matty2767

Hi John

Whilst you are collecting the information that the guys have suggested, what does your emlite meter say you have generated since installation? And what month of 2015 did you get the panels

Matt

Cardew

John_Pead wrote: »

Thank you all for your comments. The company's literature definitely promised a saving in electricity used. I have carried out a survey of our electricity usage over the last two years and it has definitely NOT gone down. We do use most heavy electric user appliances during sunlight hours and not at the same time.

The PV panels must save some electricity.


Do you have gas CH and/or an immersion heater?


IIRC there was a scenario a few years ago where someone with gas CH left on their immersion heater during the day thinking that the PV panels contribution to heating water would save money. That of course would not be the case for much of the time and would lead to an increase in electrical consumption.

Martyn1981

John_Pead wrote: »

Thank you all for your comments. The company's literature definitely promised a saving in electricity used. I have carried out a survey of our electricity usage over the last two years and it has definitely NOT gone down. We do use most heavy electric user appliances during sunlight hours and not at the same time.

Hiya John. Sounds like you are doing everything exactly right, so unless you can think of some large addition to your consumption, then there does seem to be a problem.

I only monitor generation, to help judge when to switch things on, though the MKI eyeball is pretty good at that too. Sounds like the system you are looking for will help with monitoring and spotting a problem, but do check your import meter type, and perhaps contact the PV company and ask them to have a look - as you know, you really should see a noticeable drop in import, so something has gone wrong.

One other thought, but you need a leccy expert like Dave Fowler to comment, but how is the system cabled? The cable from the TGM (total generation meter) that records PV generation should go into the consumer unit, [so you'd have a slot marked 'PV in', in the same way that other slots will be marked 'ring main upstairs', 'downstairs lights' etc] so your house can use the leccy first. I doubt this would happen, but if the cabling goes to the mains, before the import meter, then you wouldn't see any benefit.

Mart.

Dave_Fowler

Just a few points:

I've had a reasonable scan through this thread and can't find details of the readings from your generation meter - is the pv system actually generating, and how does this compare with what is expected for your roof in your area. The PVGIS website should provide a good estimate of what should be generated.

If your system is generating correctly, you should find your electricity consumption is reduced.

As has been said by Martyn, check the make and model of your import meter - the one which is used by your supplier to produce your electricity bills. - one make and model is known to work incorrectly with solar panels.

I've only known of one instance where the generation meter along with the whole PV system has been connected to the wrong side of your import meter. The cable from the PV generation meter should be connected either to your consumer unit (with all the fuses and switches) or to a junction box between the consumer unit and the import meter.

Dave F