Shared solar in a 13-unit building (different owners): one inverter per apartment vs. centralized in

Got a garden office running off a single Victron MultiPlus and a couple of Fogstar Drift 100Ah batteries, so I'm no stranger to keeping things simple — but 13 separate owners sharing infrastructure sounds like the kind of project that'd make a solicitor weep into their Earl Grey.

Had a similar micro version of this debate when a mate and I briefly considered sharing a battery bank across two garden studios on the same plot. We gave up after about 20 minutes because who owns the BMS when it trips at 2am? Multiply that headache by 13 and you've got a proper nightmare.

My instinct for a multi-owner setup would be one inverter/battery system per unit, full stop. Yes, it's less efficient, but:

• Each owner controls their own Victron (or whatever) app
• Billing disputes become someone else's problem
• One dodgy BMS doesn't black out the whole block
• Easier to finance, insure, and eventually sell

A centralised system sounds elegant until flat 7 decides they want to switch to Octopus and flat 11 is never home and everyone argues about whether the bloke on the top floor is hogging capacity for his crypto rig.

The only scenario where I'd seriously consider central is if there's a building management company with iron-clad contractual authority over the shared kit. Even then, good luck getting 13 owners to agree on which brand to use.

Anyone here actually pulled off shared battery storage across multiple independent owners in the UK or similar? Curious whether the legal side is the bigger beast than the technical one.

HarryWalker | 312 posts

@RockyMender Good starting point having that Victron experience! The ownership complexity is honestly the bigger headache than the technical side here. With 13 separate owners, I'd seriously lean towards individual inverters per unit — keeps billing straightforward, avoids endless disputes when someone's away for a month and doesn't want to subsidise their neighbours, and if one system faults it doesn't drag everyone down.

Centralised sounds elegant on paper but who owns the inverter when it needs replacing? Who decides on upgrades? You'll want watertight legal agreements either way, but individual setups make the governance side considerably less fraught.

Worth looking into whether a residents' management company structure would work for your building — makes shared infrastructure decisions much cleaner legally speaking.

The ownership angle is what would keep me up at night honestly. Even with my little shepherd's hut setup I've had headaches just deciding whether to add a second Fogstar battery — imagine that decision multiplied across 13 parties who all paid different amounts and have different usage habits.

From a purely technical standpoint a centralised inverter/battery bank sounds elegant but the BMS situation gets complicated fast. Who owns which cells? What happens when one flat's owner wants to upgrade capacity?

Per-unit Victron setups might feel redundant but at least when something goes wrong you're dealing with one owner's problem not a committee meeting. Seen this with communal solar on a farm near me — the wiring was fine, the humans were the issue.

Definitely worth getting a solicitor familiar with shared ownership property to draft something before a single panel goes on the roof.

Del6 | 847 posts

@RockyMender Thirteen separate owners sharing a single centralised inverter is asking for trouble the moment someone stops paying their share of maintenance costs or wants to sell up. I'd lean toward individual inverters per unit despite the higher upfront cost — each owner has clear responsibility for their own kit, and one faulty system doesn't drag everyone else down.

That said, shared DC busbars with individual metering could be a middle ground worth exploring if the building's common areas are already jointly managed through a proper residents' management company. The legal framework already existing makes a huge difference.

Have you looked at whether there's a freeholder or management company involved? That changes the conversation significantly, as they could potentially hold the infrastructure on behalf of all leaseholders rather than trying to apportion ownership between thirteen individuals.