### Water Heating

What Does It Cost To Heat Your Water?

It is generally accepted that it costs about 1¢ to 2¢ to heat a gallon of water.

(The exact amount will depend on the efficiency of your water heater, whether you use gas or electric and exactly what your electric or gas costs are).

### Energy Required To Heat 1000 Gallons Of Water

A Btu, or British thermal unit, is the amount of energy needed to raise one pound of water from 60°F to 61°F at sea level.

A gallon of water weighs 8.33 lbs. If the incoming water is 60°F and we want to raise it to 140°F, that is a 80°F rise.

Heating a gallon of water thus requires 8.33 x 80 = 667 Btu’s, at 100% efficiency.

### Cost To Heat Water Using Natural Gas

A typical gas tank water heater is only 59% efficient. It takes 667 - 59% = 1131 Btu’s to heat a gallon of water with gas

One therm is 100,000 Btu’s. One Btu is 0.00001 therms 1131 Btu’s is 0.0113 therms.

It will take 0.0113 therms to heat a gallon of water, or 0.0113 x 1000 = 11.31 therms to heat 1000 gallons.

At \$1.20 /therm, it costs 11.31 x \$1.20 =  \$13.58 to heat 1000 gallons of water!

### ELECTRICITY

Cost To Heat Water Using Electricity?

A typical electric water heater is 90.4 to 95% efficient or 92.7% average efficiency.

It takes 667 - 92.7% = 720 Btu’s to heat a gallon of water using electricity.

One kWh is 3413 Btu’s. One Btu is 0.000293 kWh.

667 Btu’s x 0.000293 kWh/Btu = 0.195 kWh

It will take 0.195 kWh to heat a gallon of water, or 0.195 x 1000 = 195 kWh to heat 1000 gallons?

At \$0.11/kWh, it costs 195 x \$0.11 \$21.45 to heat 1000 gallons of water!