Home Energy: Water Heating

Most homes use storage (tank‑type) water heaters, either gas or electric. When you turn on a hot water tap, heated water flows from the top of the tank to your pipes, while cold water enters at the bottom to replace it. This incoming cold water triggers the heating system.

Gas storage water heaters use a burner (and often a sealed combustion system in newer models) to heat water, while electric heaters typically rely on upper and lower heating elements inside the tank. Both systems maintain stored water at a set temperature so it’s available when needed.

All storage water heaters are equipped with a temperature and pressure relief (TPR) valve, a critical safety feature that releases hot water or steam if pressure or temperature builds up excessively. The valve should be tested annually according to the manufacturer’s instructions.

Safety note: Modern gas water heaters often use electronic ignition and sealed combustion. Homeowners should follow manufacturer instructions for maintenance and contact a licensed professional for gas controls, venting, or ignition issues.

You don’t need a new water heater to start saving energy. These five proven strategies can improve efficiency and extend equipment life:
1. Lower the Temperature: Many water heaters are set hotter than necessary. A setting of 120°F is sufficient for most households and can reduce water‑heating energy use by 6–10 percent, while also slowing mineral buildup and reducing scalding risk.
2. Insulate the Tank: If your storage water heater is located in an unconditioned space (garage, basement, utility room), an insulation blanket can reduce standby heat losses. Modern high‑efficiency tanks may already be well insulated—check the manufacturer’s guidance before adding insulation.
3. Insulate Hot Water Pipes: Insulating the first 3–6 feet of hot water piping reduces heat loss and delivers hot water to taps faster, saving both energy and water.
4. Flush the Tank Periodically: Sediment buildup reduces efficiency and tank capacity. Draining a small amount of water from the bottom of the tank once or twice per year helps remove mineral deposits, especially in areas with hard water.
5. Use Heat Traps: Heat traps prevent warm water from rising out of the tank when not in use. Most newer water heaters include built‑in heat traps, but older systems may benefit from a simple retrofit installed by a plumber.

Today’s water heater market offers more efficient—and cleaner—options than ever before:

• High‑Efficiency Gas Storage Water Heaters: These units improve on conventional designs with better insulation, advanced burners, and stronger heat recovery. Look for higher tank R‑values and ENERGY STAR certification.
• Gas Condensing Water Heaters: Condensing models capture additional heat from combustion gases, achieving much higher efficiencies than standard gas tanks.
• Heat Pump Water Heaters (HPWHs): Heat pump water heaters use electricity to move heat from the surrounding air into the tank rather than generating heat directly. They are among the most efficient options available, using up to 60–70 percent less energy than standard electric resistance heaters. Federal, state, and utility incentives often make these systems more affordable.
• Tankless (On‑Demand) Water Heaters: Tankless systems heat water only when needed, eliminating standby losses. They can offer unlimited hot water but must be properly sized to meet household demand and often require electrical or gas upgrades.
• Solar Water Heating: Solar thermal systems use rooftop collectors to preheat water, reducing conventional energy use. These systems typically require a backup heater and work best for households with good solar access.