What is a water heater?

What this means for your home project

1. Read the existing heater’s nameplate or yellow label and record its gallon capacity for the sizing discussion. Source: ENERGY STAR, read 2026-11-06.
2. Look for a manufacture date on the tank label and record it if present. Source: ENERGY STAR, read 2026-11-06.
3. For a heat-pump installation, request a written scope describing how the installer will manage condensate; the reply should name the drainage approach. Source: ENERGY STAR, read 2026-11-06.
4. When changing from a fuel-based heater to a heat-pump model, ask whether the breaker box needs additional electrical capacity; record the installer’s assessment. Source: ENERGY STAR, read 2026-11-06.

What size water heater do I need?

Water-heater size starts with your current tank’s capacity and household demand. ENERGY STAR (read 2026-11-06) locates that capacity on the "nameplate or yellow Energy Guide sticker". For storage models, also request first-hour rating—the gallons delivered in an hour starting fully heated—so the proposal describes delivery as well as tank volume. (source)

“Use the gallon capacity of your current storage water heater, if you already have one, as a starting point.” (source) “You can find the water heater's capacity or volume on its nameplate or yellow Energy Guide sticker.” (source) “You may want to purchase a larger unit if you have added or are planning to add more occupants to your household or a new shower, faucet, dishwasher or washer that will be in frequent use.” (source) “First Hour Rating (FHR): An estimate of the maximum volume of hot water in gallons that a storage water heater can supply within an hour that begins with the water heater fully heated.” (source) “The FHR is measured at a 125°F outlet temperature in the Uniform Energy Factor test method.” (source)

When should I consider replacing my water heater?

Water-heater replacement deserves consideration when the unit is "more than 10 years old", according to ENERGY STAR (read 2026-11-06). Read the tank label for a manufacture date; when the date is absent, the brand and serial number can help establish age. The advice is to consider replacement before an emergency. (source)

“If you suspect your water heater is more than 10 years old—it is time to consider replacing it before you’re left with an emergency decision.” (source) “To determine the age of your water heater, you’ll need to identify the Brand Name and Serial Number for your unit.” (source) “In some cases, the date of manufacture is printed on the same tank label where the serial number is located.” (source) “If not, you will need to consult an online water heater industry resource to determine how to read the serial number in a way that will decode the manufacturing date.” (source)

What are signs my water heater’s failing or may need significant repair?

Water-heater warning signs include corrosion, leaking water and unusual noise. ENERGY STAR (read 2026-11-06) describes "unusual noises, rumblings, or vibrations" as signs the heater is straining. Ask a contractor to assess those observations: the agency warns that ignoring problems can lead to sudden failure, tank rupture and water damage. (source)

“Corrosion is a sign that the water heater is breaking down.” (source) “Whether the corrosion is around the water lines or on the unit itself, it is a sign of deterioration that can lead to weakening the system and contributing to the water heater failing.” (source) “Water leaking can get worse and not only be damaging to the water heater itself, but potentially the area and things around it.” (source) “If your water heater is making unusual noises, rumblings, or vibrations, it is likely straining to operate correctly.” (source) “Ignoring these issues can lead to sudden failure of the water heater, cold water, and in some cases, tank rupture and water damage to the floor and carpets.” (source)

What is Uniform Energy Factor and Why Does it Matter?

Uniform Energy Factor (UEF) measures water-heater overall efficiency. ENERGY STAR (read 2026-11-06) explains that "The higher the UEF value is, the more efficient the water heater." The rating uses DOE’s test standard 10 CFR Part 430, Subpart B, Appendix E; first-hour rating separately describes hot-water delivery. (source)

“Uniform Energy Factor (UEF): The newest measure of water heater overall efficiency.” (source) “The higher the UEF value is, the more efficient the water heater.” (source) “UEF is determined by the Department of Energy’s test method outlined in 10 CFR Part 430, Subpart B, Appendix E.” (source) See the ENERGY STAR passage quoted above.

What goes into the cost of installing heat-pump water heaters?

Heat-pump water-heater installation depends on tank size and the work around the unit. ENERGY STAR (read 2026-11-06) describes tanks ranging "from 40 to 80 gallons" and identifies condensate drainage, carpentry for a louvered door, and possible electrical-capacity expansion when switching from fuel. Ask which of those items the proposed installation includes. (source)

“The tank size is one of the most important factors in determining cost.” (source) “Heat pump water heater tanks range in size from 40 to 80 gallons, with larger tanks typically landing on the more expensive side.” (source) “Heat pump water heaters capture moisture from the surrounding air in the form of condensate.” (source) “In traditional mechanical rooms and garages, this water can be routed to a floor drain.” (source) “In other locations, condensation management will need to be addressed by a contractor and may add an additional cost to installation.” (source) “Carpentry work, such as installing a louvered door may increase the cost of a heat pump water heater installation.” (source) “If you are switching from a fuel-based water heater, you may need to expand the electrical capacity of your home at the breaker box.” (source) “Capping the gas: When converting from gas to a heat pump water heater, the installer must also cap the gas line at some point leading up to the water heater.” (source)

Sources

• Heat Pump Water Heaters — ENERGY STAR; read 2026-11-06.
• Water Heater Key Product Criteria — ENERGY STAR; read 2026-11-06.
• When Should You Replace Your Water Heater? — ENERGY STAR; published 2024-02-02; read 2026-11-06.
• What Goes into the Cost of Installing a Heat Pump Water Heater? — ENERGY STAR; published 2024-02-02; read 2026-11-06.