9kW solar, 30kWh LFP, two years off-grid…

Two years ago I disconnected from the utility grid at my 1,400 sq ft cabin in central Idaho. Here's the honest after-action report.

System as built

9kW of Canadian Solar panels (south-facing, 25° tilt)
30kWh LiFePO4 battery bank (120 CATL 100Ah cells in 48V configuration)
5kW Victron MultiPlus-II inverter/charger
80A Victron SmartSolar MPPT charge controller
2.5kW Honda EU2200i generator for backup
Chevy Bolt EV (charges from solar during the day)

What worked perfectly
The Victron ecosystem. The MultiPlus, SmartSolar, and Cerbo GX talk to each other seamlessly over VE.Bus and VE.Direct. I can monitor everything from a phone app, set up automations (if battery > 90% and grid not available, export to dump load), and get detailed historical data. It just works.

The CATL cells have been outstanding. 24 months in, capacity is sitting at 98.2% on my monthly test cycle.

Summer is genuinely abundant. June through August I'm producing 50–55kWh/day on average. The battery is full by 10am and I'm running the A/C, the well pump, the EV charger, and still exporting to a dump load (hot water heater) by noon.

What failed
Generator integration was more annoying than expected. The Honda EU2200i is a great generator, but 2.5kW is only marginally enough to run the MultiPlus in charger mode while also powering the house. On two occasions I overloaded it during particularly cold cloudy stretches. I've since added a Victron Cerbo relay to automatically throttle charger input current when generator frequency drops, which fixed it, but it took two weeks to diagnose.

My first cable management was a disaster. I underestimated how much heat the connections near the battery bank would generate during high charge/discharge cycles. Nothing caught fire, but I had one terminal connection loosen from thermal cycling and drop voltage, triggering a BMS fault. Redo your connections with proper torque specs, check them at 6 months, and use a thermal camera if you have access to one.

What I'd do differently
Add a 3kW wind turbine. My worst solar production is December–February when days are short and snow covers the panels (even tilted ones). I have access to moderate steady winds during those months, and wind generation is perfectly complementary to solar — it tends to be windier when it's cloudier. This is my next project.

Go bigger on battery. 30kWh feels adequate most of the time, but a 5-day overcast stretch in November had me running the generator every afternoon. I'd go 40kWh if I were building from scratch.

Anyone else running off-grid in a cold climate? I'm specifically curious about winter production numbers and how you're handling snow on panels.

The wind turbine suggestion is interesting — what turbine are you looking at? My read of the market is that small residential wind turbines (under 5kW) have a pretty poor track record for reliability and actual production vs. rated output. The good ones (Bergey, Primus) are expensive and the cheap ones are junk. Has your research pointed to a specific model you trust?

Wyoming wind hybrid here. The Bergey Excel is what I'd recommend if budget allows — seen them run 8+ years without blade issues. The Primus AIR 40 has reports of blade fatigue failures at 5–6 years in my research. Budget for blade replacement on the Primus if you go that route.

On the snow + panels issue: there's an interesting design choice here. Steeper tilt (45–60°) sheds snow much better than a typical 20–30° optimized-for-annual-production tilt. If your worst production is winter and you have snow load, you might accept a 5–8% annual production decrease to significantly improve winter performance. Worth modeling in PVWatts with your specific location.

PNW off-grid 12 months in. Steeper tilt for snow shed is exactly what I did — 50° tilt on my array even though my annual-optimal would be 38°. I lose maybe 6% annual production but gained meaningful January and February generation. Worth it for anyone with serious snow load.

Your generator integration issues are almost universal in off-grid setups and don't get discussed enough. The interaction between a generator's frequency under load, the MultiPlus's "UPS mode" behavior, and the auto-throttle is genuinely complex. The Cerbo relay solution you landed on is the right one — I've also seen people use a Victron generator start/stop relay that automatically starts the generator when SoC drops below a threshold and stops it at a higher threshold, which avoids the deep discharge condition entirely.

Covered generator integration on an episode earlier this year — the Cerbo relay auto-throttle solution you landed on is exactly what every off-grid installer I've talked to recommends after the first overload incident. Nobody anticipates it during design. It should be a standard checklist item.

@karl Looking at the Primus Wind Power AIR 40. It's expensive (~$800 for the turbine alone) but has a solid long-term track record. The real cost is the tower — a proper guyed tilt-up tower for a residential turbine runs $1,500–3,000 depending on height. You need enough height to get into clean wind above ground turbulence. I've talked to three people who installed cheap Chinese turbines and every single one had a blade failure or controller failure within 18 months. Not doing that.

The winter output numbers are what I keep modeling for Portland. My 4kW array generates maybe 7–8kWh on a clear January day, which is almost nothing. How much does your generator actually run between November and February? That specific number is the one I can't find anywhere and it's what's holding me back from taking the full off-grid transition seriously.

9kW solar, 30kWh LFP, two years off-grid. Real numbers vs. what I modeled.