Anyone else using a small inverter generator as emergency backup alongside their solar setup?

We've had a rough few weeks up here in Yorkshire — three days straight of heavy overcast and our 400W panel array barely scraped 0.3kWh a day. The LiFePO4 bank (200Ah, 12V) got down to about 20% SOC which made me a bit nervous. We've got a wood burner for heat so that's fine, but the fridge and the router were starting to become a concern.

I ended up firing up a little Honda EU22i that's been sitting in the shed. Ran it for about 90 minutes, got roughly 18A into the battery via a 30A DC-DC charger, and that was enough to top things back up to 80% and keep us comfortable. Used maybe half a litre of petrol. Honestly quite pleased with how it performed — quiet enough not to annoy the neighbours and the sine wave output played nicely with all the kit.

What I'm wondering is whether anyone has a more automated or tidier solution for this kind of thing. Is there a way to set up an automatic transfer switch or some kind of relay so the generator kicks in (or at least prompts you) when SOC drops below a threshold? And does anyone bother keeping a jerry can of treated petrol year-round, or do you just nip to the garage when needed? Keen to hear how others handle the "rubbish week in winter" problem.

KenGraham | Posts: 847

@JulieEvans Yep, exactly why I added a little Honda EU22i to my setup last year — best decision I've made. I run it for roughly 90 minutes to top the batteries back up rather than letting it idle for hours. Much more fuel-efficient that way.

One thing worth considering: a proper battery-to-generator automated transfer switch means you can set a low SOC trigger and it kicks in without you having to think about it. Takes the stress out of those grim January weeks entirely.

I'd also suggest keeping a note of your actual fuel consumption per kWh delivered — helps you budget properly for extended bad spells. Mine works out to about 0.6 litres per kWh at sensible load, which is manageable.

How are you currently connecting it to your system? Direct to the inverter-charger or something else?

ZFS_OffGrid | Posts: 213

Got a Jackery 2000 Pro sat as buffer but yeah, small genny is the sensible belt-and-braces move. Been running a cheap Chinese 2kW inverter genny alongside my Victron kit in the static for two winters now. Does the job.

@JulieEvans 400W into a 200Ah bank is tight even in decent weather tbh. You'll hit that 20% wall pretty quick with consecutive grey days — Yorkshire winters aren't exactly Malaga are they.

One thing worth flagging — get a proper transfer switch or at minimum wire it through your Victron charger rather than bodging it direct. Seen a few horror stories on here.

Also check your genny runs quietly enough if you're on a site. Some wardens get funny about it.

IslandOffGrid | Posts: 156

This thread hits close to home. My shepherd's hut setup on a Scottish island means I intimately know what three grey days in a row feels like — it's basically November through February up here.

What changed everything for me was pairing a Kipor IG2600 with my Victron MPPT and a 200Ah Fogstar Drift bank. The Victron's two-wire BMS integration means the genny kicks in automatically via an AC charger when SOC drops below a threshold I've set.

One thing nobody's mentioned yet — runtime economy. Rather than trickle-charging for hours, I bulk-charge back to 80% in one concentrated session, then let solar finish the job. Genny fuel consumption drops noticeably that way.

@JulieEvans — worth checking your charger's absorption settings too. Yorkshire winters deserve a properly tuned system.

SilverTrekker | Posts: 432

@JulieEvans Yorkshire winters are brutal for solar — I feel your pain! One thing worth considering alongside whatever genny you go for: set a SOC trigger point before you hit 20%. I run mine at 30% now, gives you a gentler top-up cycle rather than a recovery charge, which is kinder to the cells long-term.

Also, runtime efficiency matters hugely with these small inverter gennys — running at 50-60% load is the sweet spot rather than trickle-charging. I batch my charging sessions to coincide with cooking times so the generator's doing proper work rather than just idling away burning fuel.

@IslandOffGrid curious what runtime you're getting per litre up there — wind must compensate somewhat but those prolonged low-pressure systems are relentless.

BorderExplorer | Posts: 847

@JulieEvans Snap — I'm on the Scottish Borders and December/January can be genuinely dire for generation. After a similar experience a couple of years back, I picked up a Honda EU22i and it's been brilliant. The inverter output is clean enough to charge the LiFePO4 directly through a decent DC-DC charger without worrying about waveform issues.

One thing nobody's mentioned yet — keep a log of your "solar drought" days. Once you've got a season's worth of data, you can right-size your backup runtime needs rather than just guessing. I found I only actually needed the genny three or four times last winter once I'd properly matched my loads to realistic winter generation figures.

Running it for a focused 2-3 hour charge rather than trickling all day also saves considerably on fuel costs.