Can grid-tie solar inverters run on batteries instead of photovoltaic panels?

Interesting one this — I've seen a few people try it and the results are mixed.

Technically, a grid-tie inverter needs to see a DC input voltage within its MPPT operating window, and a battery bank can fall within that range depending on your battery chemistry and string configuration. So in theory, yes. In practice, it's a bit more complicated.

The problem is that grid-tie inverters use MPPT to constantly hunt for peak power, which is fine with panels but with a battery you're essentially giving it a near-flat voltage source. Some inverters will just latch on and draw hard — potentially pulling more current than your battery can safely deliver. No BMS is going to thank you for that.

I had a brief experiment with an old SMA unit at my static caravan setup before I switched everything over to a proper Victron off-grid system. Got it running briefly but it was janky and I didn't trust it long-term.

The other elephant in the room — grid-tie inverters need to sync to the mains. No mains, no output. Anti-islanding protection will just shut them down. So unless you're feeding back to a live grid, you're stuck anyway.

If the goal is running AC loads from batteries, honestly just get a proper hybrid or off-grid inverter. Victron Multiplus, Growatt, even a basic Renogy unit will do the job properly without the headaches.

Has anyone actually got a grid-tie running reliably on a battery bank long-term? Curious if there's a setup that actually works cleanly.

@BigAl yes, technically it works — batteries sit happily within most MPPT voltage windows if you size the bank correctly. A 48V LiFePO4 system running at say 52–54V fits neatly inside many string inverter input ranges.

The fundamental problem is anti-islanding protection. Grid-tie inverters are legally required (G98/G99 in the UK) to shut down when they can't detect grid frequency. No grid connection = inverter throws a tantrum and refuses to play.

Some grey-market units from the Far East have this "disabled" — but running those legally in the UK is a different conversation entirely.

The practical upshot: you'd be better off with a Victron Multiplus II, which is designed for exactly this use case. Trying to bodge a grid-tie inverter onto batteries is solving the wrong problem with the wrong tool.

@GoldenNomad that's useful to know — but I'm wondering what happens when the battery voltage drops under load? Most grid-tie inverters I've looked at have a fairly narrow lower cutoff, and I'd imagine a battery bank sagging under heavy draw could trip the inverter off unexpectedly?

Also, presumably the grid-tie inverter has no low-voltage disconnect, so you'd risk taking your batteries down too far? For something like my narrowboat setup I'd need that protection built in somewhere.

Has anyone actually measured the efficiency losses doing it this way versus a proper off-grid inverter like a Victron Multiplus? Feels like you'd be adding unnecessary complexity for marginal savings.

@AshSeeker that voltage sag issue is the real killer in practice. Had a similar headache on the narrowboat when I was experimenting with mismatched kit — the inverter just trips out the moment voltage dips below its MPPT floor.

Worth noting that grid-tie inverters also need a live grid connection to sync with before they'll output anything — that's a legal/safety requirement in the UK under G98/G99. So even if the battery voltage holds steady, you're not running "off-grid" in any meaningful sense.

If you actually want battery-based inversion, a Victron Multiplus or similar is the proper tool. Grid-tie units are just fundamentally designed around a different use case — trying to bodge them onto a battery bank is more trouble than it's worth.

@CaddyDream the other sneaky problem nobody mentions is that grid-tie inverters are designed to export, so the moment the grid goes down they anti-island and shut off — meaning you've built yourself a very expensive paperweight that works perfectly until you actually need it. 🤦 If you want batteries doing proper inverter work, just grab a Victron Multiplus and stop torturing yourself — my garden office runs off one and it hasn't thrown a wobbly once.