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.