Electricity: If water and power are combined in your bill, subtract those items that give reference to water before you divide total cost of the bill by kilowatt hours used. Do not be concerned with "number of days," "energy costs," and separately listed taxes and surcharges
Natural gas: Divide total cost at bottom of the bill by the number of therms used. Do not be concerned with "billing factor," "adjusted therms," "scheduled billing rates," or any separately listed taxes.
Water: Divide the total charges by the number of "100 cubic feet." If the water is part of your electric bill, water charges are the total of "water used" and "sewer service charge."
Laundry Room Utility Costs
There are 748 gallons of water per 100 cubic feet
One thermal unit (therm) = 100,000 btu.
One wash load = one dry load.
Washer water consumption per total cycle is 34 gallons. Since water rates are quoted at so much per 100 cubic feet, 34 gallons = .045 of 100 cubic feet. That means there are 22 washer cycles for every 100 cubic feet of water.
To compute what part of the water is hot water, we are assuming that for every four coin-operated loads washed, two will use hot water wash at 18 gallons per cycle, one will use warm water at 8 gallons per cycle, and one will use only cold water for a total of 44 gallons and an average of 11 gallons of hot water per cycle. This is most important since approximately 90% of the energy used in a washing machine goes to making water hot. It takes 11,000 btu's of gas or 0.11 therms to heat 11 gallons of water.
It takes 3.3 therms per month to keep 11 gallons of water hot in a water heater.
Washing machines use .30 kilowatts of electricity per cycle
Dryer energy is quoted at maximum (we assume the heater is running for the complete cycle).
Gas dryers use an average of 17,000 btu per complete cycle, or 0.17 therm. By national average for every four loads dried, two will be at high heat, one will be at medium heat, and one at low heat. Average maximum btu consumption at high heat is 25,000 per hour and medium and low are both 20,000, so 2 times 25,000 plus 2 times 20,000 equals 90,000 per hour, divided by 3/4 (45 minute cycle), and divided again by four loads equals 17,000 btu per complete cycle or 0.17 therms. Electric usage in a gas dryer will average 0.5 kilowatt hours per load.
An all-electric dryer will use 3.3 kilowatt hours in a 45-minute cycle.
Industry averages show 72 cycles per month on both washers and dryers (this equals 2.2 cycles per day).
Your cycles per month can be computed by dividing the gross amount collected by the total of one washer vend and the amount of money necessary to run the dryer for 45 minutes - for example, a $0.50 wash and a $0.50 dry for 45 minutes would equal $1.00 per cycle.
1. Water uses:
0.045 of 100 cubic feet of water,
0.300 kwh of electricity,
and 0.110 therms of gas