All About Domestic Hot Water

Choosing a Water Heating System

Water heater energy usage in a typical house is the 2nd largest (14-18%) of your total energy bill. According to the DOE, the average home uses 64 gallons of water per day and spends $400-$600 per year on water heating energy.

When selecting a hot water heater look at the total cost; the unit, installation, energy- by type of fuel, maintenance, life expectancy, and tax and rebate incentives.

Pay attention to comparisons between energy efficient water heaters.
Consumer Reports states today’s federal efficiency standards means that water heaters have improved energy savings. Heaters with fewer than 55 gallons should see about a 4% efficiency boost. Water heaters larger than 55 gallons should reduce your utility bill by 25-50%, depending on the technology of the heater.


Fuel Considerations:

1.    The fuel type availability will be a factor in your selection.

2.    If you have more than 1 option for fuel, compare utility rates in relation to the fuel efficiency of the unit you are considering. For example, an electric unit might be more efficient than gas even though gas rates are lower.

3.    Natural Wood- available in limited areas of the country and not allowed in urban areas.

Fuel Types:

4.    Electricity- can be used in all heater types and in combination with space heating.

5.    Natural Gas- can be used in all heater types and in combination with space heating.
        Gas vs Electric Water Heaters

6.    Propane- cannot be used with a heat pump. Can be used with space heating.

7.    Fuel Oil- cannot be used with tankless or heat pumps. Can be used with space heating.

8.    Solar- Available throughout the United States -- most abundantly in the Southwest -- for solar water heaters.

9.    Geothermal Energy- Available throughout the United States used in conjunction with geothermal heat pump system for space heating and cooling.

Types of Water Heaters:

Natural Wood Burning Furnace- typically used in combination with space heating. Requires a storage tank and abundant supply of wood.

Conventional storage water heaters offer a ready reservoir (storage tank) of hot water.

Tankless or Demand-type Water Heaters- heat water directly when the water flows from the hot water valve at the point of use without the use of a storage tank.

Heat Pump Water Heater.jpg

Heat Pump Water Heaters- removes and adds heat from the air instead of generating heat directly for providing hot water.

Geothermal Energy- Available throughout the United States to those who will have or already have a geothermal heat pump system installed in their homes for space heating and cooling.

Geothermal Energy- Available throughout the United States to those who will have or already have a geothermal heat pump system installed in their homes for space heating and cooling.

Solar Water Heaters- use the sun's heat to provide hot water. Needs a pump system and storage tank. Can be used in combination with other fuels for back up on cloudy days.

Tankless Coil and Indirect Water Heaters- use a home's space heating system to heat water.

Stove Pipe Water Heater- used in combination with space heating wood furnace.

Or if all else fails.

You should also consider:

1.    Efficiency- for maximum performance and operating expenses look for a water heater with an energy efficiency Energy Factor (EF). This is a rating for the amount of hot water produced per unit of fuel consumed. The range should be (0.75 - 0.95.)

a.    Recovery Efficiency- how efficiently the heat is transfering to the water.

b.    Stand by losses- The % of heat lost per hour from the stored hot water compared to the water’s heat.

c.    Cycling Losses- The amount of heat lost as the water is circulated thru the tank or pipes.

d.    Size- calculate the unit size needed based on your usage and peak demand.

e.    Storage Tanks- Look for models with tanks that have a thermal resistance (R-Value) of R-12 to R-25.

2.    Calculate your desired FHR.- Consumer Reports advises that when sizing a hot water heater, consider the first-hour rating (FHR) for a tank water heater when doing a water heater energy usage comparison. The FHR indicates how much hot water can be delivered in the first hour. Then, depending on the specific model, you can look at the time the heater requires to return to its full FHR. The worksheet example shows for a household with a total peak hour demand of 36 gallons, the FHR should be 34 to 38 gallons. Calculate your FHR.

3.    Maintenance- regular maintenance will prolong the life the water heater and improve performance.

a.    Storage Tanks- every 3 months check valves and flush a quart of water and check the temperature.

b.    Storage Tanks- replace anode rods. Frequency depends on the water heater and if you have hard water.

c.    Solar- can be every 3-5 years and should be done by a solar contractor.

Tax Credits and Rebates:

1.    Here is a link to a site that lists utilities around the country that offer rebates:

2.    Here is a link that lists rebates by zip code:

3.    Federal Tax Credits: Water Heaters (non-solar) Electric Heat Pump. Gas Oil, or Propane.

4.    Check local tax credits and rebates from utilities and government incentives.

Tips to reduce your water heating bill:

1.    Conserve and use less water.

a.    Buy a new energy efficient water heater.

b.    Wash clothes in cold water.

c.    Repair links. A drip per second equals $1/month.

d.    Use low flow fixtures. Cost about $10-$20 and saves 25-60% less hot water.

e.    Turn down the temperature. Recommended is 120 degrees F. Turn down the thermostat while on vacation.

f.     Buy energy star fixtures.

g.    Insulate hot water pipes with neoprene pipe insulation.