Guides / Batteries & Inverters
Pure Sine vs Modified Sine Inverters
How the two types of inverter differ, which appliances and tools need pure sine, and what to check before you buy.
An inverter turns your battery's DC power into 240V AC, so you can run normal appliances and tools. The two main types are pure sine wave and modified sine wave, and the difference matters for what you can safely run.
1. What's the difference?
- Pure sine wave inverters produce smooth AC, much like the power from the grid.
- Modified sine wave inverters produce a stepped, square-ish wave. It's cheaper to make, but it's a rough copy of grid power.
2. What can struggle on modified sine
- Motors and compressors, such as fridges, freezers, air compressors and pumps. They can run hotter, noisier and less efficiently.
- Variable-speed tools and some battery chargers, including some cordless tool chargers.
- Microwaves, some LED lights and dimmers, and anything with sensitive electronics.
- Audio gear, which may hum or buzz.
Some gear will work on modified sine, some will work poorly, and some may be damaged. Check the appliance's manual if you're unsure.
3. Which one to buy
For a home or workshop, buy pure sine. The price gap has shrunk a lot, and pure sine runs everything a modified sine inverter can, plus the things it can't. Modified sine only makes sense for simple loads like basic lights or heaters on a very tight budget.
4. What to check on the label
- Input voltage: it must match your battery system voltage (12V, 24V or 48V). See 12V, 24V or 48V? Picking Your System Voltage.
- Continuous rating: the power it can supply all day. Size it above the total of everything you'll run at once.
- Surge rating: the short burst it can supply when a motor starts. See Running Power Tools Off Solar.
- Idle draw: the power the inverter uses just being on. On a small system, a big inverter left on all night can flatten the battery.
- Australian compliance: buy one sold for the Australian market, with Australian outlets and compliance markings.
5. Plugging in vs wiring in
Plugging an appliance straight into the inverter's own outlet is how portable inverters are meant to be used. Connecting an inverter to a building's wiring, a switchboard or a power point circuit is a different job.
Safety: in Australia, any work on 240V AC wiring, including connecting an inverter, battery or solar system to a home's switchboard or fixed wiring, must be done by a licensed electrician. Grid-connected systems also need approval from your electricity network.
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