Import at cheap rate and export direct back to the grid

We had new solar panels and a battery fitted a few weeks ago. A little complicated as we have panels from 10 years ago on a fit tariff. The plan was to capture the excess generation from the existing panels and from the new panels into the battery which we were told could be done. It seemed to work and we charged up overnight at cheap rate. As it was fitted in February we did not get any excess from our existing panels to be able to monitor.

In may we did and we went back to the installer and sent screen shots showing that although the new panels charged up any excess from the existing panels was still being exported tot he grid even though the battery was not full. He replied to say he had gone to givenenergy support who had reset the inverter and all should be goo now, please monitor.

Now all seems to not work, we have had every combination. app says no import but octopus online says we are and charging us, change settings now we are charging the battery and not importing when sunny, looks great but as soon as the sun goes we export all the battery to the grid. Final great one we charge overnight at cheap rate and at 4.30 as soon as we stop charging it exports it all back to octopus, they must think it is great, see screen shot.

I have checked on the portal log and I can see the support read our 'grid safety standard' set it to a number and then set it back again. My installer is not replying, please can someone, (givenergy) help us.

1. if you have existing panels on a fit tariff is it possible to take the excess to the battery and if so how
2. if we cannot what do we do to get the system to work at least aswell as it did do

We only have a 5kwh battery but an airsource heat pump was installed in march so we will need more and we need to work out how much more.

Susan There's quite a lot to unpack in that. I think there are two separate issues:

1. You want to integrate an existing FIT system
2. Your GE system is currently dumping battery to grid at the first opportunity it gets.

I can't say much about (1), except that I believe there are two separate payments: a generation component for just having solar at all; and an export component, which can be based on deemed export, but I have read on here that if you are able to measure how much you export, you must switch to metered export. (It does seem slightly iffy to take a payment for deemed export if you're actually shoving it all into a battery, and then squirting it back out to the grid under a different guise. Power laundering, as it were 😆 )

On (2), 'eco' mode should generally behave sensibly. A common problem is that people read the documentation on 'timed discharge' and decide, quite reasonably, that it describes what they want. Unfortunately, the documentation is completely wrong - it does not "cover home demand", it dumps to the grid at fixed (usually max) power. However, if the battery is charging from solar when it's sunny, it might not be that. And reset-to-defaults should fix that.

Is it possible that the CT clamp is fitted incorrectly. Then the system might believe there is some consumption that needs to be covered, and is discharging accordingly.

Could you describe, or post a picture of, the first tab on the app (the animation with energy flow between the various pieces), both when it's sunny and the battery, and once the solar has dropped below the consumption threshold and the battery is discharging.

Oh, and I forgot to ask, what model of GE inverter do you have? And it's probably not relevant, but what sort of inverter does the old FIT system use ?

I think it all comes down to where the CT clamp is connected and thus whether it can detect the FIT energy going to the grid or not.

I have two gen 1 hybrid inverters (with batteries) and an older AC coupled FIT inverter. The hybrid inverters would only capture and charge the batteries from their own solar, the FIT power always went to the home or was exported.
However since upgrading to the latest 191/193 firmware my inverters now seek to use all excess export to charge the batteries. I understand that the gen 2 and 3 hybrids do this already.

One other thing, it may be that you are maximising the charge rate of your inverter with your new solar and the FIT generation. Anything generated by FIT over the inverter limit will be exported.

And as DD says, you'll have to give up the deemed export if you want to be paid for export or if you have a smart meter that can measure the export.

Thanks for you replies
On point 1, agree on the being paid for an export that does not happen. We do not have a meter for it, we are paid on deemed export and know that this may be a part of the fit we drop. But had not planned on dropping it until we got a setup that worked first. Out existing panels have a solar edge inverter and it is about the same power as the new panels. So in the peak of the summer we will be producing about 20kwh a day.

The two pictures are from 11th may when it was sunny, so you can see we exported and filled up the battery and then when the battery was full we exported it all. I don't think we got to the inverter limits for filling the battery that shows up on the overnight fill up.

The second screen print is from today. I did have other setting on and following comments just went to eco mode, you can see when that happened and now I am filling the battery. But the final screen print is from yesterday which worked okay until the sun went down and dumped it all back to the grid.

Nothing has changed to the clip since we started. I would admit I dont really understand how the original panels can charge the battery but the electrician assured us it could and would.

Susan I would admit I dont really understand how the original panels can charge the battery but the electrician assured us it could and would.

Yes, I'm a bit hazy on that. But I assume that if the inverter sees that there is exporting going on, and it knows it's not doing it, then it assumes that there are some other solar panels around, and charges the battery anyway.

On another way of looking at it: eco mode is trying to keep grid use close to 0. If there's any import, it increases discharge rate / reduces charge rate to try to cover it. It seems reasonable to suppose that if there's any export, it reduces discharge rate / increases charge rate.

Susan until the sun went down and dumped it all back to the grid.

Did it..? Light blue indicates consumption, so it believes that it was discharging the battery to cover consumption. In the middle chart (below "battery capacity") there are tiny pulses of red underneath, which indicate that it's seeing a tiny bit of import. This comes back to the CT clamp - the system doesn't measure consumption, but it infers it from the difference between what it's generating and grid activity. An incorrect CT clamp would screw this up. That said, the red on the chart does look entirely reasonable, suggesting that it is behaving correctly.

It might be useful to include grid activity on the other charts. On the app, it's easy to toggle each component on/off which might make things clearer.

Thank you, that is helpful, I think we will need to monitor it for a bit now they have done the reset and we have a better understanding of what the various settings do. I will set the charge from the grid to low tonight though, a bit too frustrating to pay for it and then give it straight back 🙂

Susan I will set the charge from the grid to low tonight though, a bit too frustrating to pay for it and then give it straight back 🙂

What tariff are you on? Unless it's a time of day tariff like economy 7 which you can get without a smart meter, there's usually no benefits to charging overnight

DD On another way of looking at it: eco mode is trying to keep grid use close to 0. If there's any import, it increases discharge rate / reduces charge rate to try to cover it. It seems reasonable to suppose that if there's any export, it reduces discharge rate / increases charge rate.

This is how I believe my hybrid inverter is now working on the latest firmware. I've seen the inverter charging at a higher rate than it's own panels are supplying, the extra AC charge coming from the FIT panels. I'm very pleased it works like this now, an unexpected benefit

There are huge benefits on the EON Next Drive V6 tariff- 7 hours overnight at 6.7p - don’t need an E V, just a battery.

You then get into the possibility of exporting the battery to the grid at 16.5p with EON and let the sun fill your battery.

Is it possible to set the system to do this in summer?

Bobby123 yes you can do program your inverter easily for Eon drive.

Just set Eco mode on and a full charge of the battery overnight. All solar generated will go to the grid at 16.5p. If your house load exceeds the solar generation at any point in the day the battery will support the demand and be filled up afterward by the sun.

For best return you want to empty the battery in the evening but this gets a bit more complicated to manage