# Generator Calculating The Output

Calculating the generator’s output is important for deciding what size generator is right for you. Doing this is very simple and will save you some headaches in the long run.

## Watts = Volts x Amps

Generators can only put out a finite amount of power. Companies use watts to rate a generator’s output. The wattage is calculated by multiplying the voltage by the electrical device’s load capacity in amperage (Watts = Volts x Amps). For example, a generator may be listed as 1,500 watts delivering 120 volts.

## Generator Amps = Watts / Volts

Now you can find the amperage that it can output at 120 volts by dividing the watts by the volts (Amps = Watts / Volts). So a 1,500 watt generator delivering 120 volts can output 12.5 amps.

## Generator Dual voltage

Some generators are dual voltage and also output 240 volts. Find the amps available at the higher voltage. Now the 1,500 watt generator is delivering 6.25 amps at 240 volts. Just to note, some generators are not be able to deliver 120V and 240V at the same time, so check the specs.

## What are you powering?

Whether it’s a few things around the house or your camping equipment — the total load from the devices that you are powering cannot exceed the generator’s output. Take a look at the electrical spec label or owners manual for the devices that you want to power with the portable generator. Then add the watts up in order to figure out what portable generator that you need. Generators are usually listed with a constant/continuous load specification, as well. This is the amount of power that the generator can safely put out for an extended period of time. Some devices also require a large amount of starting wattage compared to their running wattage. For example, a washing machine may require 750W while running, but 2,300W while starting. You may want to differentiate what will be constantly running as well as the maximum amount of power that you’ll need.

## How many watts?

 Air Compressors, 1/2 HP 1,500 – 3,000W Circular Saw, 7-1/4″ 1,000 – 2,500W Electric Chainsaw, 14″ 800 – 1,500W Electric Drill, 1/4″ & 3/8″ 300 – 600W Electric Drill, 1/2″ 350 – 1,200W Grinders, 6″ 1,000 – 2,600W Jig Saw 200 – 800W Paint Sprayer 800 – 1,300W Portable Oil Heater 900 – 1,000W Router 900 – 1,000W Sander, 4″ Belt 700 – 1,500W Soldering Iron 100 – 300W 10 Amp Battery Charger 300 – 400W Electric Motors* Required Wattage 1/6 HP, 460 Watt 340 – 850W 1/4 HP, 725 Watt 450 – 1,050W 1/3 HP, 800 Watt 560 – 1,300W 1/2 HP, 970 Watt 760 – 1,800W 3/4 HP, 1,340 Watt 1,080 – 2,600W 1 HP, 1,700 Watt 1,250 – 3,000W 1-1/2 HP, 2,300 Watt 1,600 – 4,200W Household Uses Required Wattage Air Conditioner, 10,000 BTU 2,000 – 3,000W Coffee Pot 1,000 – 1,500W Electric Heater 1,000 – 2,000W Electric Stove (one element) 750 – 1,800W Gas Furnace 300 – 1,500W Hair Dryer 800 – 1,500W Iron 1,000 – 1,500W Microwave 500 – 1,500W Oil Furnace 400 – 2,000W Radio 30 – 100W Refrigerator / Freezer 600 – 2,500W Sump Pump 800 – 3,000W Television 100 – 350W Toaster 1,100 – 1,700W Water Pump 1,000 – 3,000W

*Electric motors require at least three times more wattage when first starting than when running.

## More Resources

When choosing a generator, it’s a good idea to oversize it. If your load is going to be 1,500W then it may be best to look a generator that can deliver 2,500W.

WARNING: NEVER back feed your home’s electrical system with an extension cord and a portable generator. This may cause severe damage to all electrical appliances and it creates an electrical hazard to all persons.

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