Hi Guys
I have a 15 year old solar array 3kwh with a line converter
I decided it was time to renew and upgrade the system while still keeping my valuable fit payments, currently 73p per kwh for what i generated.
So a new 3.6 hybrid inverter and 9.5 kwh battery fitted. Eon accepted the changes and my fit register updated accordingly.
1 month from installation all seemed to be doing what was expected, had some issues trying to get my head around the lodgic of the new bi directional net meter, which is required to keep my fit generation payments.
I’m with Eon next drive v3 so can take advantage of the cheap off peak rates to charge the battery, as i said all well and good and the net meter readings seemed to track the app solar generation figures until the last 2 days when had wall to wall sunshine which meant i actually exported about 3.5 kwhs to the grid.
I always start the day with a fully charged battery so yesterday because i had full battery and very little load from the house the majority of the solar generation was exported to the grid,to my horror the net meter the next day did not show any net gain from the last 2 days but a reduced reading that corresponded to the exported figure.
This is a really big deal fore as you can imagine, any help would be warmly welcomed
Are you reading the wrong value on the meter, or is there only one value?
I would assume net would be the line to read, not exported.
Hi and thanks for your help.
Yes im reading the net value
I would add that my inverter settings are
Eco with a timed charge between midnight and 7.00 am this enables me to start the day with a full battery which is only required to service the house for 17 hrs therefore giving me more capacity, if youget my drift
Maybe the installer wired the meter wrong? Get them to check it?
Yes that is in hand thank you.
Can you confirm that in the event of correct installation and equipment that system should work and give me the generation figures from the solar panels as expected, in other word’s as before the upgrade.
Many thx in advance
It wont be exactly correct because of the losses converting AC to DC and back to AC (e.g. buying electric during cheap off peak periods).
That process might be 80% efficient at worst and therefore for every 1.2kW put into the battery from the grid you’ll get 1kW back out. Therefore the register for import to the battery will increment more than the register for export to the house.
Sorry i didn’t quite mean that, i knew about conversion losses its more to about the fit generation figures and will they be the same with the new system compared to the original system prior to the upgrade
Blockquote
Or did you mean yes with the losses
You can’t get generation figures from a net meter.
It’ll be no less accurate than a string inverter if that was also measured after conversion to AC (which they normally would be!).
The difference is, as above, the net reading will be slightly erroded the more you charge from the grid due to the measurement being in AC and the losses between AC>DC>AC.
So you wont get paid for as much generation as you would if you never used grid charging.
But if you have the option of grid charging and a good off peak rate it would be silly not to use the battery to its full potential.
Great thx for the clarification. You’re right of course and i can accept a loss of income from the the generation, as you say its offset by the savings from off peak electricity…
But to go full circle I’m seeing the generation figures reduce when i export from the panels and thats surely not right
I’m not sure what a bi-directional net meter is? It sounds like it’s supposed to increment when you’re consuming and decrement when you’re exporting, like eg an old wheel type meter. But that doesn’t sound right for solar.
Normally, you’d get a smart meter, which has several registers and records incoming and exporting separately. Then you also need a meter on the output from the solar system, which records all power generated, whether used in the house or not. And if you’re paid for what you generate, that would be your FIT meter. Does that make sense?
I agree with the second para above from Pjnightingale. He’s described what I have on my system whoch was upgraded to a 9.5kWh battery in 2023. The original PV generation meter was retained with the PV connected to the rest of the system down stream of the PV meter thus retaining my FIT payment stream.
The problem is this is a hybrid.
You have to account for electric stored in the battery from the grid.
It is measured at the AC end, not DC end.
So that measurement would include grid charging and discharging.
I have one of those meters too, although dont have FIT.
Hi Guys and thanks for your inputs.
You clearly have kept your old line inverter and had a new ac coupled inverter fitted but I went down a different route. Because my original inverter was 15 years old i thought it was best (and advised) to go with a hybrid inverter which on the dc side of the of the system, this is allowed by the fit scheme provided you change the original generation meter to a bidirectional net meter, this will record your pv generation and so it was installed. One month on the meter was tracking the pv generation untill we had a few days of good sunshine, enought to charge the battery or even export to the grid and this is where my problems started. Everything that went to the battery or was exported to the grid because the battery was full pushed the net meter reading backwards .
So you can imagine when the summer months come at this rate i shall be paying into the fit scheme rather than receiving any payments
Nightmare
Having an installation like mine is not uncommon and i was hoping that someone out there could help with my problems
I’d not heard of net metering, but I’ve read the wiki page on it now. It seems it’s designed to allow the owner of a solar generator to “bank” generated units and use them later. I can’t quite get my head round that, and the battery introduces another complication. Surely if your FIT contract pays for everything you generate, can’t you just report what you generate?
No, because FIT want the reading from an official meter and not from a system such as GivEnergy portal.
FIT meters are usually (I assume always) measuring the AC into the home, not the DC from the panels.
Therefore as above, you have to calculate the net discharge from the system (deduct the mains charging).
The above link is a good read and one of the reasons i chose a hybrid inverter. There is no suggestions of the problems im facing.
Very puzzled, confused and upset by it all
Like i said in my original post when the solar panels meet the requirements of the house the net meter readings track what the app portal shows but as soon as the pv power starts to charge the battery it goes in the net reading reduces and never recovers so i have to start from a new base again. Be clear the battery is charged every night to 100 % from the grid as its a cheap rate and discharges through the day to service the property