Installer sayas NO

I have a recently fitted AC3.0 and a 5.2kWh battery, fed from 10 year-old solar panels and the original inverter. I am currently giving away solar generation to the grid soon after 1pm every day, so I clearly need more battery.
When the sun goes in, freezer, oven and microwave draw more together than the new battery and inverter can supply. I understood from discussion on this forum that a second inverter with the increased storage would allow the house to draw twice as much from storage, thus avoiding drawing from the grid. The installer of the new kit says no, I am limited by the original inverter. Is it me, or is it him?

ianconstable I think you're both right but not saying the same. If you added another battery to your existing inverter, the power output (kW) wouldn't change (as the inverter is the bottleneck) but your ability to store and use more battery energy (kWh) would increase. This, I think is what the installer is talking about.

If you added another inverter with battery (your question here), you would increase the potential for both power and energy output. Givenergy have a real downer on multi-inverter installations, saying they're not recommended. However, there are lots of people out here with either dual AC3s or dual hybrids (including us). Our maximum output from battery-powered (gen1) inverters is 5kW (2x2.5kW) and maximum energy is 16.4kWh (2x8.2kWh), which we consume in the depths of winter when there's no PV to speak of.

Apparently, gen1 hybrids have been given away free with batteries. If you wanted to add battery capacity, you could consider replacing your (presumably FIT) inverter with a hybrid. You'd have to get agreement from your FIT tariff supplier to you adding battery on the DC side, but as long as your MCS installer put in a meter that does the net generation sums, you'd be fine. Net generation simply subtracts the import (to battery from grid) from the export (PV + battery to home) to provide the difference; PV to home, so your 50% deemed export continue to be calculated.

I think the main reasons why Givenergy have a downer on multi-inverter installations is that the AOI is out now (so why would you install multiple AC3s?) and multi-inverter installations are a pain to get the portal doing sums correctly.

Tim
Thanks, that's very helpful.
Ian

Tim Tim, If you add a second inverter do you have to reapply for G98 or G99, or is this based on the number of panels?

Tim hopefully the EMS will address this regarding the portal data making sense. I’d love to replace my system with AIO but it just doesn’t make financial sense..😂. If it had been out when I ordered mine it’s what I would have gone with.

ianconstable If you were going to go to the trouble of changing your original FIT Inverter and add another battery then you might as well just punt for the AIO.
Price wise they are very similar and you would get a larger battery 13.5kw and 6kw max draw of AC energy use.

Karen If you add a second inverter do you have to reapply for G98 or G99, or is this based on the number of panels?

If you add microgeneration (ie inverter) capacity, you would need another DNO application. Since there is an existing inverter, the total possible output from the premises would exceed 16A/3.68kW and therefore a G98 would not apply; it would have to be G99. If all of the microgeneration installed is type tested to G98 (ie each inverter has G98 on the manufacturer's data plate), you can apply for a G99 Fast track, otherwise it's a full G99; or rather, that was the case prior to May when the regulations were superceded by G100, but the principle is likely to be the same.

Tim if your replacing kit with the same output then I would imagine no new application is require though?

The g99 fast track facilitates higher inverter values than the g98, but places a requirement on the amount exported to grid. Our g99 was fast track and our inverter is 5kw. Grid export is limited to 3.68kw through a software setting (not accessible to me).