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The fridge hums, the lights flicker, and the inverter you bought on a whim shuts off every time the compressor kicks in. That is the moment inverter types start to matter, because the type you pick decides which loads will run and which will not. An inverter turns battery power into household AC, and the types differ by the wave they make, the size of the loads they can run, and whether they also charge the battery. This guide walks through each type in turn, so you can match the inverter to the loads you plan to run.
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Inverter types: the quick answer
The main inverter types are pure sine wave, modified sine wave, inverter chargers and portable inverters. A pure sine wave inverter makes smooth AC like the power from a wall outlet, and it runs fridges, motors and electronics with controls without trouble. A modified sine wave inverter makes a rougher wave and costs less, but some loads run hot or buzz on it. An inverter charger also charges the battery from a wall outlet, and a portable inverter plugs into a car outlet or clips to a battery for small loads on the move.
Pure sine wave vs modified sine wave
A pure sine wave inverter makes smooth AC like the power from a wall outlet. It runs fridges, motors, well pumps and electronics with controls without trouble, and it is the safer choice for anything with a motor or a control board. A modified sine wave inverter makes a rougher wave. It costs less than a pure sine wave inverter of the same size, and it runs lights, phone chargers and simple heaters well enough, but some loads run hot or buzz on it, and some electronics with controls will not run on it at all. If your loads include a fridge or a well pump, a pure sine wave inverter is the type to pick. See pure sine wave vs modified sine wave inverter for a side-by-side look at each wave type.
Inverter chargers
An inverter charger is an inverter with a battery charger built in. It turns battery power into household AC when the power is out, and it charges the battery from a wall outlet when the power is back. That makes it a good fit for a cabin or a home backup setup where the battery needs charging from the wall as well as from the panels. An inverter charger costs more than an inverter alone, and it needs a battery bank that matches its charging current. If your panels already charge the battery, an inverter alone may be enough.
Portable inverters and installed inverters
A portable inverter plugs into a car outlet or clips to a battery, and it suits small loads on the move: a laptop, a phone charger, a light. An installed inverter mounts near the battery bank and feeds the loads through its own outlets, and it suits larger loads that run for hours. Portable inverters cost less and move with you, while installed inverters cost more and stay put. Pick a portable inverter for trips and short outages, and an installed inverter for a cabin, an RV or a home backup setup that runs every day.
Size: continuous watts and surge capacity
Size is not a type, but it decides which type you can use. The continuous watts set the size of the loads the inverter can run without stopping, and the surge capacity sets the size of the motor it can start. A compressor fridge pulls a short spike when it starts, so the surge capacity must cover the startup draw as well as the running watts. List the loads you plan to run, add up their running watts, and pick an inverter whose continuous watts cover the total and whose surge capacity covers the largest motor on the list. A watt meter between the load and the outlet measures real use over a day, which gives a better figure than the label on the appliance. See the best watt meters for options.
How to pick the right type
Start with the loads. If the list includes a fridge, a well pump or anything with a motor, pick a pure sine wave inverter. If the list is only lights, phone chargers and simple heaters, a modified sine wave inverter will do, and it costs less. If the battery needs charging from the wall as well as from the panels, pick an inverter charger. If the inverter moves with you from the car to the campsite, pick a portable inverter. Then size it: match the continuous watts to the running watts of everything on the list, and match the surge capacity to the startup draw of the largest motor. See the best pure sine wave inverters for home backup for larger units.
FAQ: power away from the grid
What is the difference between a pure sine wave and a modified sine wave inverter?
A pure sine wave inverter makes smooth AC like the power from a wall outlet, while a modified sine wave inverter makes a rougher wave. The pure sine wave type runs fridges, motors and electronics with controls without trouble, while the modified type costs less but can make some loads run hot or buzz.
Do I need an inverter charger?
Pick an inverter charger if the battery needs charging from a wall outlet as well as from the panels, as in a cabin or a home backup setup. If the panels already charge the battery, an inverter alone is enough, and it costs less than an inverter charger.
Can a modified sine wave inverter run a fridge?
It may run, but it is not the type to pick for a fridge. A fridge compressor can run hot or buzz on a rougher wave, and the controls may not work as they should. A pure sine wave inverter is the safer choice for a fridge, a well pump or anything with a motor.
What size inverter do I need?
Add up the running watts of everything you plan to run at the same time, and pick an inverter whose continuous watts cover that total. Then check the surge capacity against the startup draw of the largest motor on the list, since a compressor pulls a short spike when it starts.
Can I use a car inverter for home backup?
A car inverter suits small loads for a short time, like a laptop or a phone charger, but it is not a home backup inverter. Home backup needs a larger inverter with strong surge capacity and a battery bank that can feed it for hours. A licensed electrician should install any inverter that connects to home wiring.
Related solar guides
See the pure sine wave vs modified sine wave inverter, the best pure sine wave inverters for home backup, the best inverters for a refrigerator and the best watt meters. See every controller and inverter guide on the site.
