There are many types and brands of power inverters. Modified Sine Wave and True Sine Wave inverters are capable of producing AC current to operate your kitchen appliances or your computer and TV sets.
Both types of power inverters come in all sizes, Some with a built in transfer switch. And some with a built in battery charger or both. Both types of inverter come with AC outlets mounted right on the front of them or are the hard wire type for conduit connections. Most all of the smaller inverters come packaged with battery post clamps or a lighter plug for your car. Starting at around 2000 watts most are hard wired. A 2000 watt inverter at 12 volts would be pulling about 166 amps. That takes some good connections and large wires. Electric motors and compressors such as what are in a refrigerator or freezer work best with true sine and do not play well with modified sine wave. Some times you can hear the sound of the wave form in the speakers of your computer or your radio. Motors make a humming sound from the flats on the square wave form of the modified sine wave.
True sine wave AKA Pure sine wave, do not have any of the above problems to worry with. If it works great in your home it will work great with Pure/True sine wave.
The hair dryer is the biggest power user that I know of at 120 volts. These things will use as much as 1800 watts of power. That is a full 15 amps which just so happens to be the breaker size in some older homes. On a 12 volt battery bank it would be about 150 amps (that is more then most car batteries have in them). Did you know you can weld metal with 60 amps of power and less?
A hair dryer justifies a 2000 watt power inverter or larger. A microwave uses around 11 amps power or about 1300 watts. With either of these two items you would need a little extra power for lighting. You don't want to eat in the dark or blow dry your hair with no lights.
Stackable power inverters are normally found in the larger sizes. Most of the bells and whistles are found in the 2000 watt range or higher. A built in and programmable battery charger is a good option in an inverter. If you are using a 24 volt battery bank you don’t have to spend the extra cash and buy a charger if it is already built into the inverter. Normal battery chargers you find in a department store are not what you would need to charge a deep cycle battery. Most will not equalize a wet cell battery or will not switch to GEL or AGM.
Some times an AC transfer switch will be built into the better inverters. This allows for the built in charger to keep the batteries charged while by-passing the inverter to power your home. But when the power goes down it auto switches to the inverter and backup power. You will never even notice it happened unless the inverter is under a heavy load.
An external stand alone transfer switch can be installed with most any inverter. It can be used as a go between the generator and the inverter. When the generator is started it disconnects the grid or inverter and charges the batteries and powers the loads. Or if the grid goes down a transfer switch would switches the load to the inverter and battery backup.
You should always start from the load end when planing what size of a solar power system you will build. Get the inverters to match the heaviest load with a little extra power. Pick the wave form type you will require, Modified Sine Wave or True Sine Wave. Will the inverter with a build in transfer switch will be useful to you or do you need to go with an external switch. Or if a transfer switch is needed at all. And do you need a built in battery charger?
Inverters are the first item of interest in a solar backup system or just a backup power system. You should look for inverters that will do what you need them to do and then size the rest of the system accordingly.
You are the only one that knows what your plans are. So you have to pick the right inverter or inverters and other components. So take a little time and put together a few numbers before you buy. Try your best to pick the inverter you will need a year from now, Because once you buy it the money is spent. If you upgrade after you build and you did not get a stackable inverter you could have a shelf item.