The first thing to know is what you plan to run at this time of emergency. The lower the number of elements or the lower the amperage, a smaller or less expensive inverter will be needed. Below I will give you a table of elements and their average energy uses, followed by a simple formula that will give you an idea of ​​the size of the inverter you will need.

Stackable Washer / Dryer: 2500 Watts

Electric chain saw: 1700 watts

Electric circular saw: 1600 Watts

Full-size microwave oven: 1400 watts

Chest Freezer: 1200 watts

Mini microwave: 1000 watts

1/3 Inch HP Submersible Pump: 920 watts

Reciprocating Saw: 720 watts

1/2 inch reversible drill: 620 watts

Coffee maker: 600 watts

Portable vacuum: 525 watts

Garden Power Tools: 475 watts

10 speed blender: 450 watts

Orbital sander: 400 watts

Home stereo: 350 watts

3/8-Inch Variable Speed ​​Drill: 320 Watts

20-inch TV / VCR Combo: 300 Watts

12-inch three-speed fan: 200 watts

Computer / Printer / Fax: 150 Watts

Quartz halogen spot: 100 watts

Mini stereo / CD player: 50 watts

8 Inch Laptop / TV: 38-45 Watts

Cell phone / camcorder charger: 10 watts

14 Volt Cordless Drill Charger: 8 Watts

If the appliance you plan to use is listed in watts, go ahead and use that number. If it’s listed in amps, you just need to use this simple formula: volts (120) X amps (listed on device) = watts. This will give you the number of watts the appliance will use. So if you had a 3 amp appliance and you wanted to find the watts, the formula would be: 120 (volts) X 3 (amps) = 360 watts.

Then you would total all the watts that you will use and get a number. Let’s say your total watt consumption is 500 watts. If that’s the case, it would be a good idea to purchase a 750 watt inverter. Always get a size larger than you think you will need, it can be useful.

The next step will be to determine where your power supply will come from. If it’s for emergency purposes, it’s most likely coming from a battery connected to your vehicle, or you may be a bit better prepared and have a battery bank connected in parallel. Since most of the people reading this are probably unfamiliar with creating a battery bank, I will only cover operating the inverter from the vehicle. The main thing to know is what type of battery you will be using. It is suggested that you have a deep cycle battery or those used for trolling motors or golf carts and that you get as many amp hours as your budget allows. A few years ago I was able to go 11 days using a 750w inverter and a 120 amp hour deep cycle battery connected to my car. I had to run the car for 10 minutes every 2 hours to run everything I had plugged in, which was a laptop, a 13 “color TV, a direct TV receiver, a laptop modem, a power light. 40 watts and a small box fan – doesn’t sound like much, but I figured I was staying at the Ritz Carlton compared to most of my neighbors.

The last thing you need to know is how long your power supply (battery) will last before it needs to be recharged. You will first need to know the wattage of all the appliances. Let’s say we have a total of 480 watts of power in use, and our inverter is powered by a 12-volt battery connected to the car. Next, we have to convert this number to find out how many amps are being used. We do this by taking the watts (480) and dividing by 12 (battery volts) and we get 40 amps. The formula is: watts / volts = amps. If we have a 120 amp hour battery, we would divide 120 (amp hours) by 40 (amps) and get 3 hours before the battery dies. It is recommended not to drain the battery below 50% of its capacity, so you may want to divide the 3 hours in half, giving you 1 1/2 hours before starting the car to recharge the battery.