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How much energy does my water heater use?
Direct Energy, November 30, 2023
4 minute read
How much energy does my water heater use?
Direct Energy, November 30, 2023
4 minute read
Your water heater is one of the more robust energy consumers among your home appliances. In the average home, the hot water heater is responsible for about 17% of the total energy use, according to the Department of Energy.
If you can calculate how much energy you expend heating water, you'll have the information you need to improve your energy efficiency and bring your water heater’s overall cost down to a minimum.
Exactly how many watts an electric water heater uses depends on several variables, including: the age and size of the unit, whether it's a tank or on-demand model, what temperature you set it to, how much hot water you use in a day, and other factors.
You can come up with a cost estimate by multiplying the amount of watts your heater uses times the price you pay per kWh, times the number of hours the heater is active per day, then divide the total by 1,000.
Typically, a hot water heater that uses a tank will run for 3 to 5 hours per day. So, a 4,000-watt heater used for 3 hours a day at 10¢ per kWh will cost $1.20 per day, about $36.50 per month, or $438 per year.
If you use a gas hot water heater, the same factors affect the cost as with their electric cousins. The formula for estimating your bill is similar as well: multiply the therms your heater uses per hour times the number of hours it runs, times the price you pay for therms.
For example, if you pay $1 per therm and use a heater that consumes .205 therms per hour for 3 hours per day, your totals come to about 62¢ per day, $18.70 per month, or $224 per year.
Generally speaking, a gas water heater costs less per month than an electric model, since natural gas prices tend to be lower than the cost of electricity.
Going by the examples given above, where the electric heater costs $438 vs. $224 for gas, you would save $214 per year using gas, although the exact numbers you see would depend on all the other variables in play, like the efficiency of your unit.
To refine your calculations, know that the amount of gas your hot water heater uses will depend on its Energy Factor, or EF rating. The higher the number, the better, with the most efficient models reflecting around .67 or 67¢ on the dollar.
If you need to purchase an electric water heater, look for models with EF ratings in the 90s. You can also look for models that use alternative methods of heating the water, such as solar heaters or heat pumps.
Tankless water heaters warm up water on demand rather than storing a reservoir that is kept hot at all times. Generally speaking, these units will consume less energy than a traditional hot water heater, which also requires you flush it from time to time to maintain its efficiency.
How much electricity tankless water heaters use will still depend on the demand you create in your home. Since they don't need to heat water when you aren't using them, tankless heaters may only run for 2 hours a day or so.
According to the Department of Energy, tankless heaters are around 24 to 34% more efficient than heaters with tanks in homes that use 41 gallons or less of hot water per day; 8 to 14% more efficient in homes that use 86 gallons of water or more per day.
Keep in mind, however, these models also cost more to purchase and may require new wiring in your house, which will offset some of your energy savings.
To reduce how much electricity or natural gas your hot water heater uses and bring your bills down, consider these tips:
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