Recommended home battery inverters + regulatory matters - help requested

JamesPa · 2026-01-04T10:01:38Z

Its probable that I will have work done on my house which will trigger a replacement CU. My plan, if I do, is to provision for all likely future upgrades at the same time. This will include circuits for EV charger, induction hob and battery inverter in addition to the existing ones for PV inverter and heat pump. I am keen to avoid the mess of separate dedicated mini CUs that the 'dedicated' battery/EV charger people tend to put in to avoid touching the main CU, hence the desire to plan and do the whole thing at once, an option which is almost certain also to be cheaper. One option Im seriously considering is to have the electrician instal the battery inverter at the same time, with batteries (perhaps Frogstar?) to be added by me when they are next discounted. This could make the whole thing particularly cost effective, finally making the battery business case pay. The PV and battery inverters will remain separate, ac coupled initially, but when my 14 year old PV inverter finally gives up the ghost I may well combine the two functions. The ability to operate as backup in case of mains failure would be useful, but perhaps not essential. Can anyone outline (or point me at) the main regulatory considerations (ie what triggers G98/99/100 - noting I already have a 3.68kW PV inverter - and can you avoid by setting the battery inverter not to export), what kit, apart from a suitable inverter, do you need to specify to allow islanding and inverter options (including ideally some example recommended makes). Im finding it difficult to unpick the BS from the truth in the various sources. I have a physics degree so don't expect to find it difficult to understand once I can get to the basics and given the basics I am confident I can complete the 'research' myself. Any pointers appreciated!

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JamesPa

(@jamespa)

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Topic starter 15/01/2026 9:07 am

Posted by: @johnnyb

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@jamespa having read through this thread I will add a few comments that might help.

Fogstar now sell their 16.1kWh battery with fire suppression built in, might help any concerns over fire safety.

If you can find a local electrician who fits a lot of solar they would be able to do eveything you need and offer a lot of advice. The electrician who fitted our PV panels and inverter didn't wire the rest of the house but I wish I had used him for everything as he would have kept things more compact around the CUs and offered better advice on what to fit and how to set it up. When I was trying to find a company for the PV panels I found several small solar companies local to me that are run by electricians who don't only fit solar panels. He did say I would need an earth stake, but we already had one fitted.

Thanks. The frogstar is the one Im potentially looking at.

I do know a good electrician but I dont think he does solar. Whenever I have contacted solar companies in the past they seem to be rather specialist, which is why I have been thinking of going down the route of general electrician and asking him to do the inverter stuff. However your suggestion is very helpful, whilst the individual companies might be specialist the electricians they employ may not be so I will also explore that route thanks.

If its going to happen at all its all going to happen all at once, firstly because its the only way it has any chance of making the business case for the battery work and secondly because I don't want a mess of sub CUs. Its either (Battery inverter + EV Charger + circuit for Induction Hob + redo CU) or nothing as far as I am concerned. Nothing remains a distinct possibility; none of this is absolutely necessary for me, I dont have to have a battery, I can continue charging my EV on a granny charger and we may never swap out gas hob for an induction hob (even though we are paying the whole standing charge just to run the hob) as we attach some value to fuel diversity. That said ~£500-600 saving annually for an investment which hopefully is ~ £K5-6 is quite attractive.

This post was modified 2 hours ago 4 times by JamesPa

4kW peak of solar PV since 2011; EV and a 1930s house which has been partially renovated to improve its efficiency. 7kW Vaillant heat pump.

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Bash

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15/01/2026 10:34 am

@jamespa

Could you just get the electrician to fit the new circuit in your CU for the battery storage to and including the rotary isolator switch, which any electrician would be happy to do.