How I understand a system works and what I'm being told by Solar company

[lennyg]

I had a 4kw system fitted last November with a Mastervolt 5500 inverter. As I understood it, all the electricity produced by the system is first used by my house with the rest not used being exported back to the grid. I understand that if my house is using 1kw and my system is producing 2kw then I will be exporting 1kw back to the grid and not drawing anything from my energy supplier. Conversely, if my house is using 2kw and my system is producing 1kw, then I would see a 1kw draw from my energy supplier.

My problem is this. If I understand the above correctly, then why does my energy fit monitor which monitors the electricity coming into the house from the national grid never show 0, i.e. even when I'm generating 2kw from my system, the incoming meter shows me still drawing generally about 800watts with most things off in the house? Is it that the (e.on) energy monitor is not that reliable or is something amiss? Before the system was fitted, my house would draw about 500w when at "idle", now I'm drawing generally a minumum of 800w according to the incoming meter.

I have asked the solar company if this is correct and they say yes, that ALL my electrcity is exported back to the grid and the energy company know how much I am using - all the research I did prior to taking the plunge on solar suggested different. Finally, does the energy meter that monitors the solar draw electricity from the mains supply?

Thanks in advance for you help

 

[MorganPVI]

Most probably the meter is seeing 800w being exported as the current is going the "other way"

 

[Scobo]

If your using one of those wireless energy monitors, it won't show an accurate figure of how much you're using as they can't tell the difference between the flow of electricity in from or out to the grid.
Only any good when your system isn't generating any power and even then, it will only be a rough guide.
I was using an Owl+USB to monitor our usage but now have it connected to the cable coming from the generation meter to monitor what were generating instead.

 

[SolarCity]

As Morgan says, your energy monitor reads electricity flow in both directions. Therefore it will show you as using say, 500w, when in fact you are exporting 500w. It is a common cause of confusion.

Unless you have an export meter fitted then the electricity supplier will have no way of knowing how much you are exporting and will in general assume your export is at 50%.

 

[lennyg]

Thanks for the advice. I think my best way forward is to continue to read my meter and see if there is a significant difference on sunny days. For example, yesterday I generated 11 KW and yet still used 17KW throughout the day from the grid. I would have expected to only use maybe 11 or 12. It looks like it's going to be a sunny weekend so I'll take readings and report back.

 

[SolarCity]

Have the installers connected the PV system to a new consumer unit?

 

[lennyg]

No, the consumer unit is 5 years old. They added a fuse to the current board.

Have the installers connected the PV system to a new consumer unit?

 

[SolarCity]

Then that rules out the possibility that they connected the PV system in the wrong place. I think you'll find that everything is fine.

 

[SRE]

I seem to remember last year in the middle of summer a number of people having problems with a particular type of electricity meter that was adding the kwh generated to the kwh used. I think it was a specific model of electricity meter (maybe Siemen) but if you have time to have a look through Martin Lewis's solar forum for the thread there was a lot of useful information. Needless to say the utility company wouldn't believe the customer until there were a lot of customers with the same problem at which point they changed the meter and it was all sorted out.

 

[Earthstore]

SRE is correct, there are some incoming meters that add your export to the import readings.
I advise my customers or check myself that the incoming meters are behaving correctly when a PV system is producing.
I hope this helps.

 

[Glen Powell]

SRE is right it is usually on PAYG meters I have heard reports on this with the Forrest contract (I must add all speculation and no proof given).

We used to give Owl meters away free of charge and connect them to a JB from the inverter using double insulated wire, the reason for this is a lot of our customers had a freebie monitor device from eon,BG and the like and we used to challenge them when one (the one we supplied) is at its highest the name of the game is to make the other one at its lowest, in other words if their one connected to their meter shows close to zero then they are using all the electricity they are generating (or its disconnected).

 

[moggy1968]

there was a thread on this problem on here recently.
It's part of the anti tamper on some electronic meters so if they were reverse wired they would still record.
If you find your energy useage has gone up after fitting your PV talk to your supplier about the meter.

 

[Glen Powell]

there was a thread on this problem on here recently.
It's part of the anti tamper on some electronic meters so if they were reverse wired they would still record.
If you find your energy useage has gone up after fitting your PV talk to your supplier about the meter.

And since Forrest are installing for council houses with PAYG meters this would make it sound a bit more feasible (yet not proven), God I have been to court too many times for lible, luckily not guilty once.

 

[SRE]

Found the info:

It's a known 'fault' with some Siemens S2AS meters that have an 'anti-tamper' programme. All the exported units are supposed to be available from an internal register - though you may have difficulty in finding an operator who understands the sitution in the foreign call centre that you're probably forced to call or getting anybody to come and correct things.

 

[danesol]

I had a 4kw system fitted last November with a Mastervolt 5500 inverter. As I understood it, all the electricity produced by the system is first used by my house with the rest not used being exported back to the grid. I understand that if my house is using 1kw and my system is producing 2kw then I will be exporting 1kw back to the grid and not drawing anything from my energy supplier. Conversely, if my house is using 2kw and my system is producing 1kw, then I would see a 1kw draw from my energy supplier.

My problem is this. If I understand the above correctly, then why does my energy fit monitor which monitors the electricity coming into the house from the national grid never show 0, i.e. even when I'm generating 2kw from my system, the incoming meter shows me still drawing generally about 800watts with most things off in the house? Is it that the (e.on) energy monitor is not that reliable or is something amiss? Before the system was fitted, my house would draw about 500w when at "idle", now I'm drawing generally a minumum of 800w according to the incoming meter.

I have asked the solar company if this is correct and they say yes, that ALL my electrcity is exported back to the grid and the energy company know how much I am using - all the research I did prior to taking the plunge on solar suggested different. Finally, does the energy meter that monitors the solar draw electricity from the mains supply?

Thanks in advance for you help

Thanks for the advice. I think my best way forward is to continue to read my meter and see if there is a significant difference on sunny days. For example, yesterday I generated 11 KW and yet still used 17KW throughout the day from the grid. I would have expected to only use maybe 11 or 12. It looks like it's going to be a sunny weekend so I'll take readings and report back.

Firstly if you have your Solar PV been fed from a spare MCB in your CU, the supplied energy meter supplied by the utility company probably wont be showing correctly, however if your tails have been spilt and your Solar PV is been fed from the spilt tails using a Henley Block - placing the sensor around the tails of the CU fed, will show or should show exactly what you are using even if your DNO stops.

However having said all that its not important really - what is important is the DNO Electric Meter reading which you take to calculate your bill and the meter reading from your new Solar PV generation meter which is used to calculate your FiTs payment at your specific tariff rate ( example 43.3p per unit ), nothing else really counts as it is really as I say of little interest abeilt pub talk as you will PAY from your DNO meter reading and you will be PAID from the generation meter reading. The additional export payment is calculated by your paying FITs supplier at 50% or your generation reading

hth

 

[Mozzerr]

Totally agree with danesol's comments above... except... having the setup as described (most succinctly I might add) has allowed me to ditch our 3kw kettle in favour of a 750w replacement!

Visually being able to see that I was always paying for my cuppa with the 3kw kettle vs hardly ever paying for it with the 750w version is really quite satisfying! Ok so I wait a bit longer for the thing to boil.. but tbh I never notice that as the Mrs. always makes my hot drinks! LOL

Cheers.

 

[darrens1973]

am I missing something here, this guy seems to be saying his PV Output is putting his energy usage up, using 17Kw when your PV has produced 11Kw seems a lot of eleccy to use. Sounds like the Meter maybe adding the PV Generation to his normal useage, I thought mine was doing this in my house. I turned all of the circuits off except the PV and waited a few hours, PV Meter had gone up but Main meter stayed the same so no issue. This is the only way to check this isnt it?

 

[danesol]

Thanks for the advice. I think my best way forward is to continue to read my meter and see if there is a significant difference on sunny days. For example, yesterday I generated 11 KW and yet still used 17KW throughout the day from the grid. I would have expected to only use maybe 11 or 12. It looks like it's going to be a sunny weekend so I'll take readings and report back.

It doesnt matter how much you generate, if you dont use it as its produced you naturally lose it to the grid and naturally get your tariff rate for this. However, if you then come home and use masses of electric, this will have to come from the grid ( as before ) as your Solar PV would be then either at low production or switched off due to no Sun.

However there is a possibility your DNO Electric Meter is measuring the generation due to the make & type it is but if you have an old clockwork meter, this wont be the case and you may go backwards at somepoint given that your Solar PV current/voltage is greater then the supplied feed from the grid.

 

[LightGEN]

Landis and Gyr (Ampey) model 5235 can be configured to meter in a number of different ways, one of which is 'Unidirectional Registration', where, as previously described, import and export energy is added together. I see in the instruction sheet for the 5235 that the meter reading is prefixed by a letter 't' to indicate this mode is in operation. Of course the meter being discussed above may not even be the type of meter I'm talking about......I'll shut up now :willy_nilly:

 

[Glen Powell]

am I missing something here, this guy seems to be saying his PV Output is putting his energy usage up, using 17Kw when your PV has produced 11Kw seems a lot of eleccy to use. Sounds like the Meter maybe adding the PV Generation to his normal useage, I thought mine was doing this in my house. I turned all of the circuits off except the PV and waited a few hours, PV Meter had gone up but Main meter stayed the same so no issue. This is the only way to check this isnt it?

As said before, there are a few meters out there that do not detect the direction of flow, if one of those meters are installed ROI will be far less than calculated, I would ask the energy provider to install an import / export meter as soon as possible or one that is able to detect bi-directional current unless they can prove the one you have is suitable for bi-directional current and therefore not effecting your ROI.