Inverters 101

What are they?
A power inverter changes DC power from a battery into conventional AC power that you can use to operate all kinds of devices ... electric lights, kitchen appliances, microwaves, power tools, TVs, radios, computers, to name just a few.

What do they do?
The inverter draws its power from a 12 Volt battery (preferably deep-cycle), or several batteries wired in parallel. The battery will need to be recharged as the power is drawn out of it by the inverter.

A very simple way to use an inverter for emergency power(such as during a power outage), is to use a car battery (with the vehicle running), and an extension cord running into the house, where you can then plug in electrical appliances.

What size should I buy? 
The size you choose depends on the watts (or amps) of what you want to run. We recommend you buy a larger model than you think you'll need (at least 10% to 20% more than your largest load).

Example: You want to power a computer with a 17" monitor, some lights,
and a radio.

Computer:

300 Watts

2 - 60 Watt lights:

120 Watts

Radio:

10 Watts

Total Needed:

430 Watts

For this application, you would need a 500 W inverter, and should give some thought to a larger one, as there will likely be a time when you wish you'd bought a bigger model ... in this example, you might decide you'd like to run a fan while you compute, or let the kids watch TV.

 

Helpful formulas
To Convert AMPS to WATTS:

Multiply: AMPS X 120 (AC voltage) = WATTS

To Calculate approximate Startup Load:

Multiply: WATTS X 2 = Starting Load

Most often the start-up load of the appliance or power tool determines whether an inverter has the capability to power it.

For example, you have a freezer with a continuous load of 4 amps, and a start-up load of 12 amps:

4 amps x 120 volts = 480 watts continuous
12 amps x 120 volts = 1440 watts starting load

You would need an inverter with peak-surge rating greater than 1440 watts.

To convert AC Watts to DC Amps:

AC Watts divided by 12 x 1.1 = DC Amps

(This is the size vehicle alternator you would need to keep up with a specific load; for example, to keep up with a continuous draw of 1000 watts, you would need a 91 amp alternator).