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Upgrading my system, how far do I go?

TRBob · 2026-04-22T13:01:08Z

*Note to admin, I wasn't sure whether to post here, in storage or in tariffs as it applies to all three*I've had 4.4kW Solar PV (South Facing Main roof) and a Gen 1 GE inverter + 2 x 2.6kWh Gen 1 GE batteries for just over 4 years now. I've also had an ASHP for just a little longer, it has worked great in tandem with the PV and batteries and Octopus Cosy tariff (had Flux that first Summer in 2023 when the prices made sense, but hasn't been worth it since for the system size). My batteries only charge/discharge at 2.5kW and we have managed, but I'd like to upgrade to a 12kW inverter and start with a 10kWh battery (pretty sold on Sigenergy, I know a few others in the forum are not sure, but I like the look of it more over a Tesla PW3). We still cook with gas, but will be going electric and on cold days will need a higher discharge rate to run the ASHP and the kitchen at the same time.If I wasn't on Cosy, say the Intelligent Go tariff, to cover the coldest days in winter I would need a lot more battery storage and I'm not sure that it would stack up financially. I'm also considering more Solar PV, we can get 4 panels on a lower south facing roof, 14 or 16 on the north facing and some on the west facing wall.What are the current options for arbitrage, isn't IOF closed now to new applicants? Axle energy? Is it worth it to get additional PV?

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TRBob

(@trbob)

Trusted Member Member

Joined: 3 years ago

Posts: 59

Topic starter 24/04/2026 12:05 pm

@old_scientist Thank you, I've found out that the Sig battery charges/discharges at 4.5kW, so I would need two to get 9kW, which I think would probably be ok. The largest draw I found in my data on a cold day was 9.5kW, but that wasn't common and it was towards the beginning of the Cosy 1pm - 4pm cheap period when we would have been load shifting.

@majordennisbloodnok The more I think about the North roof Solar PV the less sure I am, but the additional south facing low roof and the west wall I'm more and more certain of, will try modelling different scenarios. Thank you for the info on alternative inverters/batteries that is a very valid point, I'm still quite keen on Sig for a variety of reasons, but yes there is a concern there following what happened to GE, I'll research to see what other options are out there.

Mitsubishi Ecodan 8.5kW
4.4kW Solar PV
5.2 kWh Battery Storage
1983 build, 300mm loft insulation, cavity wall insulation (beads)

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Majordennisbloodnok

(@majordennisbloodnok)

Famed Member Moderator

Joined: 4 years ago

Posts: 1759

24/04/2026 12:10 pm

Posted by: @trbob

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...

@majordennisbloodnok The more I think about the North roof Solar PV the less sure I am, but the additional south facing low roof and the west wall I'm more and more certain of, will try modelling different scenarios. Thank you for the info on alternative inverters/batteries that is a very valid point, I'm still quite keen on Sig for a variety of reasons, but yes there is a concern there following what happened to GE, I'll research to see what other options are out there.

Not a problem, @trbob. Whatever you decide, if your choices are made with wider information available then I'm happy.

105 m2 bungalow in South East England
Mitsubishi Ecodan 8.5 kW air source heat pump
18 x 360W solar panels
1 x 6 kW GroWatt battery and SPH5000 inverter
1 x Myenergi Zappi
1 x VW ID3
Raised beds for home-grown veg and chickens for eggs

"Semper in excretia; sumus solum profundum variat"

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Old_Scientist

(@old_scientist)

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Joined: 2 years ago

Posts: 405

24/04/2026 1:16 pm

Posted by: @trbob

↑

@old_scientist Thank you, I've found out that the Sig battery charges/discharges at 4.5kW, so I would need two to get 9kW, which I think would probably be ok. The largest draw I found in my data on a cold day was 9.5kW, but that wasn't common and it was towards the beginning of the Cosy 1pm - 4pm cheap period when we would have been load shifting.

For comparison, my PW3 with 11.04kW inverter, will charge at 5kW (or 10kW if you add a second battery / expansion pack) and will discharge at the full 11.04kW (can actually do 11.5kW max when off grid I believe). I know you said you are not so keen on the PW3 - I'm biased 😊

It is important to understand such things if they are going to affect you, as they are not immediately obvious from reading the headline specs. Informed decisions and realistic expectations, etc.

Samsung 12kW gen6 ASHP with 50L volumiser and all new large radiators. 7.2kWp solar (south facing), Tesla PW3 (13.5kW)
Solar generation completely offsets ASHP usage annually. We no longer burn ~1600L of kerosene annually.

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