Three things to know about using a power inverter

The first thing you need to know is what you plan to run in this time of emergency. The fewer items or the lower the amperage, the smaller or less expensive inverter will be needed. Below, I’ll give you a table of items and their average energy uses, followed by a simple formula that will give you an idea of ​​the size of inverter you’ll need.
Stackable washer/dryer: 2500 watts

Electric chainsaw: 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

Halogen Quartz Spotlight: 100 Watts

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

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

Your next step will be to determine where your power supply will come from. If it’s an emergency, it’s most likely coming from a battery connected to your vehicle, or you can be a little better prepared and have a battery bank connected in parallel. Since most people reading this are probably not familiar with building a battery bank, I will only cover running the inverter from the vehicle. The main thing you need 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 draw as many amp hours as your budget allows. A few years ago I was able to get through 11 days using a 750w inverter and 120 amp hour deep cycle battery hooked up to my car. I had to run the car for 10 minutes every 2 hours to get everything connected to it to work, which was a laptop, a 13″ color TV, a direct tv receiver, a modem for the laptop, a light 40 watts and a small box fan That doesn’t sound like much, but I thought 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. First you will need to know the wattage of all appliances. Let’s say we have a total of 480 watts of power in use and we’re running our inverter off a 12 volt battery connected to the car. Next, we need to convert this number so we know 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 runs out. It is recommended not to drain the battery below 50% capacity, so you may want to split the 3 hours in half to get 1 1/2 hours before starting the car to recharge the battery.

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