3.6kw or 5kw Inverter

Hi

I have had a quote for solar panels with an estimated output of 4174kWh and two G2 5.2kWh LiFePO4 batteries (Total 10.4kw). My installer has recommended coupling this with a G2 3.6kW Hybrid Inverter.

However I was wondering whether there was any gain to be had in installing a G2 5kW Hybrid inverter instead?

I understand that the solar panel generation will be the limiting factor and that both the 3.6kw and 5.0kw inverters can only deliver 3600w from the batteries. However I have a couple of questions.

1) Would it be possible to draw 5kw from the 5kw inverter by drawing from the battery and the solar panels simultaneously?
2) Is 4174kWh of solar within the working specs of a 5kW inverter?
3) The installer has suggested that the system will be more inefficient with a 5kW inverter as opposed to a 3.6kW inverter, is this correct?

Waterski99

1. yes, 5kW would be the maximum combined PV and Battery Output
2. are you sure it's 4174kWh? or is is 4174W? W(atts) are the unit of measure for PV production, kWh is the measure for the number of watts produced over time (kW per hour)
3. not sure about it being any less efficient, the only differences really are the maximum outputs/inputs (see here: https://www.givenergy.co.uk/pdfs/products/Version%202.0/Hybrid%20Inverter%20Gen%202.pdf)

You would also need to go down the G99 route with your DNO (probably chargeable), this needs to be in place before installation.

Waterski99 if you have pervious givenergy hybrid inverter and add the new battery . 3.6 kWh only give you 3.6 kph when summer hot months . someplace grid permission needed .

Cdent are you sure it's 4174kWh?

I think that's the installer's estimate of annual PV output (based on number and capacity of panels, azimuth and angle) on which they'll provide a RoI calculation for you.

Waterski99 Would it be possible to draw 5kw from the 5kw inverter by drawing from the battery and the solar panels simultaneously?

Yes. The inverter will respond to house demand from PV and supplement any deficit from battery if available, up to the maximum of 5kW.

Waterski99 Is 4174kWh of solar within the working specs of a 5kW inverter?

Not quite sure what you mean here as I believe this figure is your installer's estimate of your annual output. At my latitude of about 53degrees, with a roof angle of about 43 degrees and an azimuth of 215 degrees, our estimated average output is about 900W/1kWp installed capacity. I have a friend close-by with a very similar orientation and roof angle and he generated about 36MWh from PV in 10 years from his 3.68kWp array.

Tim that's what I was questioning, that seems like the annual PV output, or @Waterski99 could have meant they are having a 4.174kW array installed

As a curve ball to all of this, it’s been mooted by GE that the Gen 2 stuff (and I’m going to prefix this with MIGHT as it makes no sense to me) can deliver its PV output & then battery output on top with a software update.
So the 3.6 Hybrid would be able to deliver 3.6 of solar & another 3.6 on top so 7.2 all guns blazing.

How exactly they intend to pull this off from both an install perspective (given current installs will have MCB ratings for the original) or how this escapes G98/G99 rules is beyond me but they were adamant that the head tech of GE confirmed this so we’ll see I guess.
(I suspect they’ve got it wrapped around their neck and it’s simultaneous charging rates but when questioned the response was the only reason Gen 1 can’t pull this trick is the internal bus bar is too small so I honestly don’t know what to make of that)

Sorry to derail your thread!

hoggy So the 3.6 Hybrid would be able to deliver 3.6 of solar & another 3.6 on top so 7.2 all guns blazing.

That's one heck of a beast if it is the case.

Tim Yeah just seemed a bit too good to be true for me but happy to eat that humble pie some more!

hoggy So the 3.6 Hybrid would be able to deliver 3.6 of solar & another 3.6 on top so 7.2 all guns blazing.

That would be awesome, besides the SOC issue which hopefully can be fixed in software, my only gripe with the kit I have is the max delivery to house demand. The biggest grid demand for us is when we have multiple appliances running at dinner time and to remove that for the sunny months with no extra cost would be fab.

On a separate note is this anything to worry about for post September 2022 installs?

https://ibb.co/B313TFF

I think what they are talking about is that any excess solar above 3.6kw can be sent to the battery and therefore would not effect G98. Solar edge latest battery setup has this option.

I've got a gen1 3.6 hybrid inverter and if I'm generating 4kWh for example, it sticks 2.4 of that into the battery (maximum allowed) and then the rest (1.6) into my house. How does that work?

It may be worth a new thread on this but this was the (rather disjointed) exchange:
Red = Givenergy Lead Service Engineer
Green = Me
Black & Blue = Others
I've removed chunks of pointless exchange for clarity.

Apologies for the confusion. I am having a 4.25kW array fitted. I mistakenly quoted the estimated yearly generation figure of 4174kWh.

So I guess another way of phrasing it is.

Are there any draw backs to opting for a 5kW inverter instead of the recommended 3.6kW inverter?

Waterski99 i mean i guess there must be an PV inverter efficiency curve although i dont think GE publish it. Whether its enough to justify choosing between the smaller or larger inverter i dont know. It'll not be that often that your array will be maxed out so other than to "bagsy" extra capacity from your DNO before others on your street take it id be inclined to stick with the 3.6 to not have to suffer through G99 applications personally.

Waterski99 The advantage of a 5kW inverter would be the ability to feed greater loads. If you're happy to restrict yourself to 3.68kW export, the G99 application could be a fast track one which should be returned quickly.