Inverter power
Posted: Fri Oct 10, 2025 11:22 am
Hi,
We were already supposed to have our solar up and working but our installer (SO Energy) messed us around last minute* and it’s on pause for now. Since this happened I’ve been reevaluating some of the options that they offered, and would appreciate some advice. Sorry for the post being a bit long but wanted to give details about our situation!
(*They suddenly decided we weren’t on 3 phase - the day before delivery of the equipment - when they were the ones who told us this initially (when trying to get a smart meter installed). They now said it was single phase split into two. We just had a surveyor visit from our DNO and he seemed confident it was 3 phase given the cable, and presence of a 3 fuse cut out, but just needed to confirm by checking the transformer)
The current quote is for:
9.45kWp (21 x 450w panels)
3x Ep5 batteries
H3 Smart 10kW inverter
Regarding the batteries; I was always intending to potentially upgrade in the future to a 4th but, having remeasured the space the batteries will be, think 2x EP11 batteries would fit much better!
The advice I’m looking for though is with the inverter. I don’t know if I’m overthinking this, or worrying over nothing, but am slightly concerned about the 3.8kW output limit per phase. We use quite a bit of energy (30kWh per day at the moment but will obviously be more over winter) so don’t know if this will limit our ability to use the energy we generate/store, and not have to import from the grid, as we will obviously have quite high peaks of usage. Currently the phases aren’t balanced well (at all!) but this is something we will sort out next year.
(We have an electric oven, electric water heating (immersion heaters), and electric space heating (currently fan heaters/radiators but are planning to upgrade to air-to-air heat pumps (i.e. AC): 3 outdoor units (approx 2.5kW per unit), 9 indoor units providing cooling in summer and heating in winter), and will eventually get an EV (when we can afford it!)
I had a look online to see how much the 12kW version is (and 15kW, but couldn’t find it anywhere) and found that the wholesale price is only around £40 more. If it was £100s difference then I wouldn’t consider it but £40 is effectively the same (especially given the total cost of the install).
I just don’t know if there’s any downsides that I can’t see? I have an understanding of the components and how they work but not had any practical experience so thought I’d get advice/opinions of people who know what they’re talking about (who’s not trying to sell me anything!).
The only downside that I see is the need to make a G99 application which will delay things further (but this probably the best time to do it as we wouldn’t be generating as much now anyway). Is there anything I’ve missed? Will going for the larger output power mean it’s less efficient for low loads? Will there be any compatibility issues with the batteries (min battery voltage is higher)?
My view at the moment is to go for it given the price and the ability to (potentially) use more of the energy we generate/store and be less reliant on the grid, but would appreciate any advice/opinions people have.
Thanks
We were already supposed to have our solar up and working but our installer (SO Energy) messed us around last minute* and it’s on pause for now. Since this happened I’ve been reevaluating some of the options that they offered, and would appreciate some advice. Sorry for the post being a bit long but wanted to give details about our situation!
(*They suddenly decided we weren’t on 3 phase - the day before delivery of the equipment - when they were the ones who told us this initially (when trying to get a smart meter installed). They now said it was single phase split into two. We just had a surveyor visit from our DNO and he seemed confident it was 3 phase given the cable, and presence of a 3 fuse cut out, but just needed to confirm by checking the transformer)
The current quote is for:
9.45kWp (21 x 450w panels)
3x Ep5 batteries
H3 Smart 10kW inverter
Regarding the batteries; I was always intending to potentially upgrade in the future to a 4th but, having remeasured the space the batteries will be, think 2x EP11 batteries would fit much better!
The advice I’m looking for though is with the inverter. I don’t know if I’m overthinking this, or worrying over nothing, but am slightly concerned about the 3.8kW output limit per phase. We use quite a bit of energy (30kWh per day at the moment but will obviously be more over winter) so don’t know if this will limit our ability to use the energy we generate/store, and not have to import from the grid, as we will obviously have quite high peaks of usage. Currently the phases aren’t balanced well (at all!) but this is something we will sort out next year.
(We have an electric oven, electric water heating (immersion heaters), and electric space heating (currently fan heaters/radiators but are planning to upgrade to air-to-air heat pumps (i.e. AC): 3 outdoor units (approx 2.5kW per unit), 9 indoor units providing cooling in summer and heating in winter), and will eventually get an EV (when we can afford it!)
I had a look online to see how much the 12kW version is (and 15kW, but couldn’t find it anywhere) and found that the wholesale price is only around £40 more. If it was £100s difference then I wouldn’t consider it but £40 is effectively the same (especially given the total cost of the install).
I just don’t know if there’s any downsides that I can’t see? I have an understanding of the components and how they work but not had any practical experience so thought I’d get advice/opinions of people who know what they’re talking about (who’s not trying to sell me anything!).
The only downside that I see is the need to make a G99 application which will delay things further (but this probably the best time to do it as we wouldn’t be generating as much now anyway). Is there anything I’ve missed? Will going for the larger output power mean it’s less efficient for low loads? Will there be any compatibility issues with the batteries (min battery voltage is higher)?
My view at the moment is to go for it given the price and the ability to (potentially) use more of the energy we generate/store and be less reliant on the grid, but would appreciate any advice/opinions people have.
Thanks