Energy calculation

Single-Phase Calculations

 Basic electrical theory tells us that for a single-phase system,

KW = (V × I × PF) ÷ 1,000.

 For the sake of simplicity, let's assume the power factor (PF) is unity. Therefore, the above equation becomes

kW = (V × I) ÷ 1,000.

 Solving for I, the equation becomes

I = 1,000kW ÷ V (Equation 1)

 Now, if we look at the “1,000 ÷ V” portion of this equation, you can see that by inserting the respective single-phase voltage for “V” and dividing it into the “1, 000,” you get a specific number (or constant) you can use to multiply “kW” to get the current draw of that load at the respective voltage.

 3-Phase Calculations

 For 3-phase systems, we use the following equation:

KW = (V × I × PF × 1.732) ÷ 1,000.

 Again, assuming unity PF and solving this equation for “I,” you get:

I = 1,000kW ÷ 1.732V.

Symbol            Prefix               factor              Example

pico                 p                      10^-12                 1pF = 10^-12F

nano                n                      10^-9                  1nF = 10^-9F

micro               μ                      10^-6                  1μA = 10^-6A

milli                 m                     10^-3                  1mA = 10^-3A

kilo                  K                     10 ³                  1KΩ = 1000Ω

mega                M                     10 ⁶                  1MHz = 10⁶Hz

giga                 G                     10 ⁹                  1GHz = 10⁹Hz

·         Common Appliances

Appliance	Est. Watts		Appliance	Est. Watts
Coffee pot (10 cup)	1200		VCR	40-60
Coffee pot (4 cup)	650		CD or DVD Player	35
Toaster	800-1500		Stereo	30-100
Cappuccino Maker	1250		Clock Radio	50
Coffee Grinder	100		AM/FM car cassette	8+
Blender	300		Satellite dish	30+
Microwave (600 to 1000 W cooking power)	1100-2000W (elec. consumption)		Vacuum cleaner	300-1100
Waffle iron	1200		Mini Christmas lights (50)	25
Hot plate	1200		Space Heater	1000-1500
Frying pan	1200		Iron	1000
Toaster Oven	1200		Washing machine	920
Blow dryer	900-1500		12" 3 speed table fan	230
Computer - laptop - pc & monitor - printer-inkjet	50-75 200-400 60-75		TV - 25" color - 19" color TV or monitor - 12" b&w 13" color TV/VCR Combo	300 160 30 230
*Refrigerator/Freezer	600		Game Console (X-Box)	100
*Freezer	500-800		*Furnace Fan (1/3hp)	1200

·         Common Tools

Tool	Est. Watts		Appliance	Est. Watts
Jig Saw	300		1/4" drill	250
Band Saw	1200		3/8" drill	500
Table Saw	1800		1/2" drill	750
6 1/2" circ. saw	1000		Shop Vac 5 hp	1000
7 1/4" circ. saw	1200+		*Sabre Saw	500
8 1/4" circ. saw	1800		*Portable Grinder	1380
Disc Sander	1200		*Electric Chain Saw 14"	1200
Makita Chop Saw	1550		*Airless Sprayer 1/2 hp	600
Makita Cut Off Saw	1000		*Air Compressor 1 hp	2000