Inverter basics
Off-Grid Inverters Made Simple
An inverter is the part that turns your stored battery power into the normal household AC that runs your appliances. It's what lets you plug a laptop, fridge, or coffee maker into an off-grid system. Getting the right type and size matters, so this guide keeps it simple and points you to the inverters worth buying.
How to choose
How to pick an inverter
Choose pure sine wave
Pure sine power is clean and safe for sensitive gear like laptops, fridges, and CPAPs. Modified sine is cheaper but can buzz, run hot, or damage some devices.
Size it for your biggest load
An inverter has to handle your heaviest device running at once. Add up the watts of what you might run together, then leave some headroom.
Match the voltage to your battery
A 12V battery needs a 12V inverter, a 48V bank needs a 48V inverter. They have to agree or nothing works.
Watch for surge ratings
Motors and pumps draw a big spike when they start. Make sure the inverter's surge rating can handle that brief jump, not just the steady draw.
Pure sine vs modified sine
Pure sine or modified sine?
Both types turn battery DC into household AC. The difference is the shape of that power. Pure sine matches the smooth wave from a wall outlet, so anything you plug in runs the way its maker designed it to. Modified sine imitates that wave with a blocky, stepped one, which is cheaper to make and rougher on some gear.
The short answer: buy pure sine. Consider modified sine only when everything you run is a simple resistive load, like an incandescent bulb or a basic heater, or a device whose maker approves it, and the budget is tight.
| What matters | Pure sine | Modified sine |
|---|---|---|
| Power quality | Smooth, like the grid | Stepped, blocky wave |
| Motors, pumps and compressors | Run quieter and cooler | Can hum, run hot or wear early |
| Sensitive electronics, clocks and timers | Run as designed | Some misbehave or refuse to run |
| CPAP machines | Check the exact device manual and required output | Only models the maker approves |
| Simple resistive loads | Works | Works |
| Upfront price | Higher | Lower |
| Peace of mind | Confirm device compatibility and output ratings | Check each device first |
- Pure sine suits nearly everyone. Fridges, laptops, TVs, power tools, pumps and medical gear usually run as they would at home. Still check each device's manual and power rating, especially for medical gear. Samlex, which sells both types, recommends pure sine for motor loads, sensitive electronics and anything with a built-in clock or timer.
- Modified sine suits a narrow case. A bare-bones setup running only resistive loads, or a few devices you have confirmed work on it. That list keeps shrinking as more appliances use electronic controls and variable-speed motors.
Every inverter in our off-grid inverter picks and best 2000W inverters is pure sine. To size one for a van, read what size inverter a campervan needs.
Roundups
Find the right inverter
Best Inverters for Off-Grid Solar
Pure sine picks by system size, from vans to whole-home 48V setups.
Best 2000W Pure Sine Inverter
The 12V sweet spot for vans and cabins, with the wiring logic to install one safely.
Frequently Asked Questions
What does an inverter do?
It turns the DC power stored in your battery into the AC power that household outlets and appliances use. Without one, you can only run 12V or USB devices directly off the battery.
Do I need pure sine wave?
For almost everyone, yes. Pure sine power is clean and suits most things you plug in (check each device's manual for its required output), while modified sine can make motors hum and run hot and upsets some electronics. A few devices, including some newer CPAP machines, are approved for modified sine, but checking every device is more hassle than the savings are worth.
What size inverter should I buy?
Look at the most power you'll draw at one time. If a microwave and a few lights might run together, add their watts and pick an inverter comfortably above that, with room for startup surges.
Will a pure sine inverter use more battery?
No. The waveform is about the quality of the power, not extra draw from the battery. Motors and transformers actually run cooler on pure sine, so less of your stored energy turns into wasted heat. When you compare models, look at the stated efficiency and the idle draw, since an inverter left on uses some power even with nothing plugged in.
Can I run a fridge on a modified sine inverter?
It is a gamble. A fridge compressor is a motor, and inverter makers recommend pure sine for motor loads because they run quieter and cooler on it. Many newer fridges also use electronically controlled, variable-speed compressors, which is exactly the kind of sensitive electronics pure sine is meant for, so use pure sine unless the fridge manual says otherwise.