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You are here: Home > Information Center > Frequently Asked Questions About Inverters

Frequently Asked Questions About Solar Inverters

What size do you need?
What are some common wattages of basic household devices?
What is the difference between an inverter and a converter?
Which kind of inverters are best?
What is automatic AC transfer switching?

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What size do you need?

The size of the inverter that is best for your system depends greatly upon the power requirements of the appliances that you plan on operating. Note that you will likely be operating more than one appliance at any given time – make sure the continuous rating is high enough to handle this. Your inverter must also be able to handle a surge of many loads starting at the same time.

To decide what size you need, you should calculate the total of wattage that may be needed at any one time. Then, choose an inverter that has a slightly higher output.

The size of an inverter is measured by its maximum continuous output in watts. Again, make sure that the size rating of your inverter is larger than the total wattage of all the AC loads you are planning to run at one time.

Most appliances have some sort of label or owner’s manual that should tell you its wattage, but here is a formula for converting AC amps into watts (in case you only know the amps):

AC amps X 120 volts = watts

What are some common wattages of basic household devices?
Just to give you an idea, here is a list of some approximate watts that certain appliances in your home likely use:
  • full size microwave uses between 1400 and 1750 watts
  • coffee maker about 600 watts
  • stackable washer- dryer about 2500 watts
  • computer and monitor uses 450 watts
  • blender uses 450 watts
  • refrigerator uses 360 watts
What is the difference between an inverter and a converter?
Basically, a converter takes AC and changes it to DC, while an inverter does the opposite - it takes DC and changes it to AC (in this way, an inverter is an inverted converter.)

Which kind of inverters are the best?
The cheapest ones are square wave inverters, but they are also the hardest to use and the least efficient. A modified sine wave inverter is better, but it does not necessarily work well with all appliances and equipment. It generally works well with many TVs, refrigerators, toaster, coffee makers, etc. It may not work well with digital clocks, light dimmers, and other such items. A true sine wave inverter, while a bit more pricey, produces AC power that is basically the same as what you get from your utility company.

What is automatic AC transfer switching?
If you have an inverter/charger, then it will likely incorporate an automatic transfer switch. This ensures that outside AC power is used when it is available. It will also switch the inverter from inverting mode to charging mode. This way, no stored solar electricity is lost. Instead, the batteries are charged by the outside power source.

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