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Power Calculator

Use our power calculator to help select the portable system that's right for your application. Note that all calculations are approximate. To get exact system sizing, contact a North Star Energy Services representative.

When selecting a power generation system, keep in mind the maximum (or surge) and rated AC power of the unit.  These ratings are in watts.  The maximum rating is the wattage your solar powered unit can handle for very short periods of time, such as when equipment or appliances require additional power on start up.  The rated power is generally considered to be a safe and constant level of power consumption.  All of our units are rated according to their rated load.

In order to calculate your power requirement, add up the wattages of the tools, appliances, and items you want to use with our solar energy system.  Keep in mind there are items that have resistive, or constant loads and those that have reactive loads.  For constant load items, simply add up the Amps and convert to watts.  Reactive load items require additional power when they start up.  The product's nameplate should list both the operating amps and the maximum amps.  When you do not have access to the nameplate for reactive load products, then as a guide, use the rated Amps multiplied by 3 to arrive at the total Amps required at start up. Convert this figure to watts. Note that flourescent lamps, on average, require about 1.25 times the stated wattage on start up.

Frequently, the power ratings on items are listed in Amps.  If so, then just use Ohm's Law to calculate the wattage:

Watts = Volts x Amps

Once you add up all the power requirements, you will have the total wattage.  Just remember that, in general, not all the items will be operating at once.  So even if you determined you need 4500 watts, you may be able to operate with a 3500 watt solar power system.  And it may be important the order in which you start up the items running on generator power.

Below are some typical power requirements for various categories of items and products.  This list is only meant as a guide.  Whenever possible, please refer to the ratings on your product's nameplate or contact the manufacturer.

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AVERAGE WATTAGE REQUIREMENT GUIDE
(AMPS X VOLTS = WATTS)

Household Typical
Load (Watts)
Additional Load at Startup How Many Load (Watts)
Coffee Maker 1750 0
Dishwasher
Cool Dry
700 to 1000 1400
Electric Fry Pan 1300 0
Electric Range
8-inch element
2100 0
Microwave Oven 900 watts 1200
1500
Microwave Oven 1100 watts
1500 1800
Refrigerator or Freezer 700 1800
Refrigerator/Freezer Combo
1200 to 1500 2000
Automatic Washer
1150 2300
Clothes Dryer
Electric
5300 1800
Furnace Fan, gas or fuel oil
1/8 Horsepower 300 500
1/6 Horsepower 500 750
1/4 Horsepower 600 1000
1/3 Horsepower 700 1400
1/2 Horsepower 875 2350
40W Incandescent Light 40 0
60W Incandescent Light 60 0
75W Incandescent Light 75 0
100W Incandescent Light 100 0
150W Incandescent Light 150 0
15W Flourescent Light 15 4
20W Flourescent Light 20 5
25W Flourescent Light 25 6
50W Flourescent Light 50 12
Radio
50 to 200 0
Sump Pump
1/3 Horsepower 800 1300
1/2 Horsepower 1050 2150
Television - Color 300 0
Central Air Conditioner
10,000 BTU
1500 2200
Contractor
Typical
Load
Additional Load at Startup How Many Load (Watts)
Air Compressor
1 Horsepower
1500 3000
Bench Grinder
8 inches
1400 2500
Hand Drill
1/2 inch
600 0
Belt Sander 1200 0
High-pressure Washer
1 Horsepower
1200 2400
Circular Saw, Heavy Duty
7 1/4 inches
1400 2300
Electric Chain Saw
14 inches, 2 Horsepower
1100 0
Table Saw
10 inches
1800 4500
Drills
3/8 inch 4 amps 440 600
1/2 inch 5.4 amps 600 900
Industrial Motors
Typical
Load
Additional Load at Startup How Many Load (Watts)
Split Phase
1/4 Horsepower 600 1000
1/2 Horsepower 875 2300
Capacitor Start Induction Run
1/3 Horsepower 720 1300
1 Horsepower 1600 3200
Capacitor Start Capacitor Run
1 1/2 Horsepower 2000 4000
Fan Duty
1/4 Horsepower 650 1200
Farm Equipment Typical
Load
Additional Load at Startup How Many Load (Watts)
Electric Fence, 25 miles 250 0
Milk Cooler 1100 1800
Milker (vacuum pump),
2 Horsepower
1000 2300
Portable Heater (kerosene, diesel fuel)
50,000 BTU 400 600
90,000 BTU 500 725
150,000 BTU 625 1000
Battery Charger
15 amp 380 0
60 amp with 250-amp boost
1500/5750 0
100 amp with 300-amp boost
2400/7800 0
Electric Welder
200 amp AC 9000 0
230 amp AC, at 100 amp 7800 0
Air Compressors Typical
Load
Additional Load at Startup How Many Load (Watts)
1/2 Horsepower 975 1600
1 Horsepower 1600 3000
Computers Typical
Load
Additional Load at Startup How Many Load (Watts)
Desktop 600 to 800 0
Laptop 200 to 250 0
Monitor 200 to 250 0
Monitor
LCD Flat Panel
20 to 30 0
Fax 600 to 800 0
Printer 400 to 600 0
User-defined Products/Applicances/Tools How Many Load (Watts)
Total Calculated Load (Watts):