What Size Inverter Do I Need for Off-Grid Solar?
- Size your inverter to handle the peak simultaneous wattage of all appliances you might run at once.
- Continuous watts = what the inverter handles all day. Surge watts = the brief startup spike (2–7× for motors).
- Always buy a pure sine wave inverter — modified sine wave damages sensitive electronics.
- Most off-grid cabins need 1,000–2,000W. Full homes typically need 3,000–5,000W.
- Bigger is generally better — an oversized inverter runs cooler and lasts longer.
Continuous watts vs surge watts
Every inverter has two wattage ratings:
- Continuous watts: What the inverter can deliver indefinitely. This is the rating you should size to.
- Surge (peak) watts: The brief spike the inverter can handle for 1–5 seconds during motor startup. Typically 2–3× the continuous rating.
The surge rating matters because motors (fridges, pumps, power tools) draw 3–7× their running wattage for a fraction of a second when starting. If your inverter can't handle this spike, it will trip the overload protection and shut down.
Inverter sizing calculator
Common appliance surge multipliers
| Appliance | Running watts | Surge multiplier | Startup surge |
|---|---|---|---|
| Fridge (compressor) | 100–200W | 3–5× | 300–1,000W |
| Water pump | 200–500W | 3–5× | 600–2,500W |
| Air conditioner | 1,000–2,000W | 2–3× | 2,000–6,000W |
| Washing machine | 500–1,000W | 2–3× | 1,000–3,000W |
| Power drill | 400–800W | 2–3× | 800–2,400W |
| LED lights | As rated | 1× | No surge |
| Laptop / TV | As rated | 1× | Minimal surge |
Inverter sizes and what they power
| Inverter size | Best for | Price range |
|---|---|---|
| 600W | Lights, phone, laptop, small fan | $60–$120 |
| 1,000W | Above + small fridge, TV | $100–$200 |
| 2,000W | Full cabin, water pump, most appliances | $200–$400 |
| 3,000W | Small home, washer, multiple large loads | $300–$600 |
| 5,000W | Full family home, all appliances | $500–$1,500 |
| 8,000W+ | Large home, AC, workshop tools | $1,000–$3,000 |
Best inverter brands for off-grid
- Victron MultiPlus / Phoenix: Best quality, longest lifespan, excellent monitoring. Premium price but worth it for whole-home systems. See our Victron guide.
- Growatt: Strong value for mid-range systems. Good reliability, decent support.
- Aims Power: Good US-based option for mid-range systems. Wide range of sizes.
- Renogy: Affordable and widely available. Good for smaller cabin systems. See our brand comparison.
Frequently asked questions
Can I run an air conditioner on off-grid solar?
Yes, but it requires a large system. A 1-ton mini-split AC draws 1,000–1,500W running and surges to 3,000–4,500W at startup. You'll need at least a 5,000W inverter and a large battery bank. Mini-splits are more efficient than window units and recommended for off-grid AC use.
Does inverter size affect battery life?
Indirectly. Running an inverter at 80–100% of its rating continuously generates more heat and draws higher current from batteries, both of which increase wear. Sizing your inverter 25–50% above your typical load improves efficiency and longevity.
What's the difference between an inverter and an inverter-charger?
An inverter-charger also includes a battery charger that can charge your batteries from a generator or shore power (when available). For off-grid systems with occasional generator backup, an inverter-charger is often worth the extra cost.