Water Heaters: Tank, Tankless, Commercial & Boilers

Tankless units cost more upfront but deliver continuous hot water, take up less space, and typically last longer than a tank model, often 15 to 20 years versus 8 to 12. Whether it's worth it depends on your household's hot water usage, existing gas line and venting, and how long you plan to stay in the home to recoup the higher install cost.

For a tank unit, 30 to 40 gallons typically covers 1 to 2 people, 40 to 50 gallons covers 3 to 4, and 50 gallons or more covers larger households. Tankless units are sized by flow rate in GPM rather than capacity, based on how many fixtures might run hot water at the same time.

UEF (Uniform Energy Factor) rates the efficiency of water heaters, both tank and tankless. AFUE (Annual Fuel Utilization Efficiency) rates the efficiency of boilers and furnaces. They use different test methods, so the numbers aren't directly comparable between a water heater and a boiler.

Tank water heaters typically last 8 to 12 years, while tankless units often last 15 to 20 years with proper maintenance. Sediment buildup, water quality, and how often the unit is serviced all affect actual lifespan.

Condensing tankless units run cool enough to vent with PVC, CPVC, or polypropylene pipe, while non-condensing models typically need stainless steel venting rated for higher exhaust temperatures. Always follow the manufacturer's venting specification for the specific model.

A water heater heats water for domestic use, like showers and sinks. A boiler heats water or produces steam for space heating, such as radiators or radiant floor systems, and can be paired with an indirect tank to also supply domestic hot water.

Most manufacturers recommend flushing sediment from a tank water heater annually and testing the temperature and pressure relief valve at the same time. Tankless units benefit from an annual descaling flush, especially in areas with hard water.

Gas and electrical connections, along with proper venting, generally require a licensed plumber or electrician to meet local code and keep the manufacturer's warranty valid. Some straightforward electric tank replacements are within reach for an experienced DIYer, but gas and tankless installations are best left to a professional.

This is most often caused by sediment buildup reducing the tank's effective capacity, a failing heating element or burner, or a tank that's undersized for current household demand. A licensed plumber can diagnose which of these applies to your unit.