What size hybrid inverter do I need for off-grid?

Size by surge load, not average. A 3kW steady home with a 4.5kW pump surge needs 6-8kW. For a 5kW average / 10kW surge, pick an 8-10kW hybrid (Deye, Growatt, Luxpower class). Battery current at 48V for 10kW is ~208A — the inverter's battery-current rating must clear that plus PV charge current.

Do I need generator input on an off-grid inverter?

For regions with weak winter sun, yes. Kyiv December makes only ~5.5kWh from a 5kW array vs ~8kWh load; a long cloudy stretch drains the bank. A hybrid inverter with generator input lets you run a diesel 2 hours to top up — PV alone will not carry a Ukraine winter. Most clients keep a small generator as insurance.

Which hybrid inverters work with Chinese LiFePO4?

Deye/Sunsynk (5-16kW), Growatt SPF/SPH, Luxpower, SRNE, and Voltronic clones (Axpert/MPP Solar) all speak the Pylontech CAN protocol that most Chinese 48V LiFePO4 packs use. Victron needs a custom CAN profile. Pick by your surge load and whether you need generator input + fast transfer.

How to Size a Hybrid Inverter for Off-Grid

The inverter is the only part of an off-grid system that fails loudly — when it faults, the lights go out. Most faults come from one mistake: sizing by average load instead of surge. Here is how we size it.

1. Surge, not average

List running watts, then add the biggest start surge on top. A home at 3kW steady with a 1.5kW pump that surges to 4.5kW needs a 6-8kW inverter, not 3kW. Undersize and the inverter throws a fault code every time the pump kicks in.

2. Battery voltage match

48V is standard for 5-20kW. The inverter's battery terminals must match the pack. At 48V a 5kW bank pushes ~104A; a 10kW bank ~208A. The inverter's battery-current rating must clear the load plus PV charge current, or it caps your charge and the bank never fills.

3. Size PV for the worst month

Do not size PV input from summer. Kyiv December effective sun is ~1.1h/day against ~5.5h in summer — a 5× gap. A 5kW array makes ~5.5kWh in December, short of an 8kWh load. Size the PV input generously and plan a generator inlet for long cloudy stretches; PV alone will not carry a Ukraine winter.

4. Generator input + BMS comms are non-negotiable

For off-grid, the inverter must accept a diesel/petrol generator (most hybrids do). And it must speak CAN/RS485 to the battery BMS — Pylontech profile for most Chinese 48V packs. Without BMS comms the inverter reads SOC wrong and disconnects at 30% with a full pack.

5. Idle draw and transfer speed

A 50W idle draw on a 5kWh bank wastes 1% every 24h — check it. For whole-house backup, pick a unit with a transfer relay under 20ms so the fridge never notices the grid drop. MPPT efficiency above 97% is the floor.

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