Advanced Electronics
Determining Watt-hours (Wh) Worksheet
Determine Load.
The preferred method for determining system loads is a “bottom-up” approach in which every daily
load is anticipated and summed to yield an average daily total.
For systems designed to power simple loads, such as a single water pump, electric light or other appliance, this
method is easy. Simply look at the nameplate power rating on the appliance to calculate its power consumption
in watts.
Some labels show amperage and voltage only; to obtain watts, just multiply amps by the voltage (I x V= W).
Then multiply by the number of hours it is expected to operate on an average day to obtain watt-hours (Wh) or
(H x W= Wh).
For more complex loads, such as powering a whole house, you will need to estimate all the different loads in the
house on a typical
day and sum them.
Activity #1- Determine the required Watt-hours (Wh) per day.
1.
Using the table below, make a list of the appliances you and your family use in your house on a daily
basis.
2. Once you have made your list determine the number of Watt-hours (Wh) per day that each requires.
a. To determine Wh per day, multiply the hours each appliance is used each day by the wattage
listed below. This will give you the watt-hours consumed per day for each device.
Appliance
Watts
Appliance
Watts
Appliance
Watts
Central Air Conditioner NA
5,000
Electric blanket
200
Hedge trimmer
450
Electric Clothes Dryer NA
3,400
Shaver
15
Weed eater
500
Oven
3,000
Waterpik
100
1/4” drill
250
Hair Dryer
1,538
Well Pump (1/3-1 HP)
480-1200 1/2” drill
750
Dishwasher
12001500
Laptop
Coffee Machine
1,500
Plasma TV
Microwave
1,500
Popcorn Popper
1” drill
1000
339
9” disc sander
1200
LCD TV
213
3” belt sander
1000
1,400
25” color TV
150
12” chain saw
1100
Toaster oven
1,200
19” color TV
70
14” band saw
1100
Hot Plate
1200
12” black and white TV
20
7-1/4” circular saw
900
Iron
1,100
Stereo
10-30
8-1/4” circular saw
1400
Toaster
1,100
Satellite dish
30
Refrigerator/ Freezer**
Microwave
5001500
Radiotelephone - Receive
5
20 cu. ft. (AC)
1411 watthours/day*
Room Air Conditioner NA
1,100
Radiotelephone - Transmit
40-150
16 cu. ft. (AC)
1200 watt-hours
/day*
60-250
Vacuum Cleaner
500
Lights
Freezer
Water heater
479
100 watt incandescent bulb
100
15 cu. ft. (Upright)
1240 watt-hours
/day*
Sink Waste Disposal
450
25 watt compact fluor. bulb
28
15 cu. ft. (Chest)
1080 watt-hours
/day*
Espresso Machine
360
50 watt DC incandescent
50
Cell Phone - recharge
2-4 watts
Dehumidifier
350
40 watt DC halogen
40
MP3 Player - recharge
.25-.40 watts
Blender
300
20 watt DC compact fluor.
22
Humidifier
3001000
* TV’s, VCR’s and other devices left plugged in,
but not turned on, still draw power.
CFL Bulb (60-watt equivalent)
18
Video Game Player
195
CFL Bulb (40-watt equivalent)
11
Standard TV
188
CFL Bulb (75-watt equivalent)
20
Monitor
150
CFL Bulb (100-watt equivalent)
30
Computer
120
Heaters***
Portable Fan
100
Engine Block Heater NA
Ceiling Fan
100
Portable Heater NA
1500
Can Opener
100
Waterbed Heater NA
400
Curling Iron
90
Stock Tank Heater NA
100
Stereo
60
Furnace Blower
300-1000
Cable Box
20
Clothes Dryer - Gas Heated
300-400
Clock Radio
7
Well Pump (1/3-1HP)
480-1200
**To estimate the number of hours that a
refrigerator actually operates at its maximum
wattage, divide the total time the refrigerator is
plugged in by three. Refrigerators, although
turned "on" all the time, actually cycle on and off
as needed to maintain interior temperatures.
150-1000
* The daily energy values listed here are for the most efficient units in their class and the information was obtained from Consumer
Guide to Home and the General Electric website.
3.
Next, determine the total household load in Watt-hours (Wh). To do that simply total your total watthours per day for each appliance.
a. For complex loads like households, it is sometimes difficult to anticipate every electric load.
Electric clocks, TVs, stereos and other appliances sometimes draw small amounts of power even
when they are turned off. For this reason, it is recommended that when determining your total
household watt-hours you should multiply your estimated daily load by a “fudge factor” of 1.5.
Load Calculation Chart
Name of Appliance
Watts used
per hour
Total
Hours used
per day
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
X
Total Watts
used per day
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=
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