Short answer
It must beat federal minimums by a wide margin. Heat pump tanks need a UEF of 3.30 or more (2.20 for 120-volt plug-in and split units). Gas tanks need 0.81 to 0.86 depending on size and draw, and gas tankless units need 0.95 and 2.8 GPM at a 67 F rise. Each type also needs a minimum warranty.
Key facts
- ENERGY STAR integrated heat pump water heaters must reach a UEF of at least 3.30, deliver a first-hour rating of at least 45 gallons, and carry at least a 6-year sealed-system warranty.[1]
- ENERGY STAR gas tankless water heaters need a UEF of at least 0.95 and at least 2.8 GPM over a 67 F rise.[1]
- Version 5.0 of the ENERGY STAR residential water heater specification took effect April 18, 2023.[2]
What ENERGY STAR is for water heaters
ENERGY STAR is the U.S. EPA's label for products that beat federal efficiency minimums. For water heaters, every criterion is written in UEF, the uniform energy factor that DOE's test procedure produces. Higher UEF means less energy for the same hot water. Version 5.0 of the residential water heater specification took effect April 18, 2023[2], and EPA's December 2025 planning guide still listed it as the current specification for both heat pump and gas water heaters[3].
The criteria, by type
| Type | Efficiency floor | Other requirements |
|---|---|---|
| Heat pump, integrated (240 V) | UEF 3.30 or higher[1] | First-hour rating 45 gal or more; 6-year sealed-system warranty[1] |
| Heat pump, 120 V / 15 A plug-in | UEF 2.20 or higher[1] | Same FHR and warranty[1] |
| Heat pump, split system | UEF 2.20 or higher[1] | FHR 45 gal or more; 6-year sealed-system warranty[1] |
| Gas tank, 20 to 55 gal | UEF 0.81 (medium draw) or 0.86 (high draw)[1] | 6-year warranty on the system, including parts[1] |
| Gas tank, over 55 gal | UEF 0.86 or higher[1] | FHR 51 gal or more; 6-year warranty[1] |
| Gas tankless | UEF 0.95 or higher[1] | 2.8 GPM or more over a 67 F rise; 6 years on the heat exchanger, 5 on parts[1] |
| Solar | Solar UEF 3.00 (electric backup) or 1.80 (gas backup)[1] | 10 years on the collector[1] |
Two things stand out. There is no ENERGY STAR category for standard electric resistance tanks, because none can reach these levels. And the gas levels are set at what EPA calls a high efficiency "condensing-equivalent level"[3], well above the federal minimum for gas.
How far above the federal minimum is that?
The federal floor is set by 10 CFR 430.32. A few comparisons using today's federal formulas[4]:
| Type | Federal minimum today | ENERGY STAR floor |
|---|---|---|
| Electric tank, 50 gal, medium draw | About 0.92 (0.9307 minus 0.0002 x volume)[4] | 3.30 for an integrated heat pump[1] |
| Gas tank, 40 gal, medium draw | About 0.58 (0.6483 minus 0.0017 x volume)[4] | 0.81[1] |
| Gas tankless (under 2 gal, over 50,000 Btu/h) | 0.80 to 0.81, by draw pattern[4] | 0.95[1] |
The arithmetic is ours, using the federal formulas. The federal floor for electric tanks of 20 to 55 gallons rises to 2.30 for units made from May 6, 2029[4]. See DOE water heater rules.
Why the label matters for rebates
Most rebates are tied to ENERGY STAR certification. Three examples we confirmed at the source:
- Austin Energy (TX) pays $1,000 for an ENERGY STAR hybrid or heat pump water heater of 40 gallons or more, with conditions on the warranty and the age of the unit replaced[6].
- ComEd (IL) offers $750 for an ENERGY STAR heat pump water heater bought July 1 to December 31, 2026[8].
- Nicor Gas (IL) pays $225 for an ENERGY STAR gas tank with a UEF of .86 or higher and $150 for an ENERGY STAR tankless with a UEF of .95 or higher, installed in 2026[7].
The federal 25C tax credit used ENERGY STAR-linked rules too, but the IRS says it is not allowed for property placed in service after December 31, 2025[9]. See federal tax credit status.
How to check a model
- Find the exact model number on the box, spec sheet or quote.
- Search it in the ENERGY STAR product finder[5]. The listing shows the certified UEF and first-hour rating or flow.
- Compare the rated first-hour rating (tanks) or GPM at your temperature rise (tankless) with your household's needs. Our UEF, first-hour rating and GPM guide explains the numbers.
- Read your utility's rebate rules before you buy. Some add their own conditions, such as minimum tank size or a purchase window[6][8].
Is an ENERGY STAR model always the right buy?
Not always. A heat pump water heater needs room air to pull heat from, a condensate drain, and usually a 240-volt circuit unless you choose a 120-volt model. A condensing gas tank or tankless unit needs different venting and a condensate drain. The savings depend on your fuel prices and how much hot water you use. Weigh the install cost, minus any rebate, against the lower operating cost. Our heat pump vs standard electric guide covers that trade.
When to call a pro
- To confirm a heat pump model fits your space, drain and electrical setup before you buy.
- To check venting and condensate needs for a condensing gas tank or tankless unit.
- To get the invoice, model number and permit details a utility rebate requires.
More questions
Are there ENERGY STAR standard electric tank water heaters?
No. The ENERGY STAR criteria for electric storage cover only heat pump water heaters. A standard resistance tank cannot reach the 2.20 to 3.30 UEF floors.
Does ENERGY STAR still get me a federal tax credit?
Not for 2026 installs. The IRS says the 25C credit is not allowed for property placed in service after December 31, 2025. ENERGY STAR status now matters mainly for utility and state rebates.
How do I check if a specific model is certified?
Search the model number in the ENERGY STAR product finder. The listing shows the certified UEF and first-hour rating. A sticker on the box is not enough; certification is by exact model number.
Sources
- ENERGY STAR water heater key product criteria, ENERGY STAR (U.S. EPA). Accessed 2026-10-06.
- ENERGY STAR Residential Water Heaters Version 5.0 effective date reminder, ENERGY STAR (U.S. EPA). Accessed 2026-10-06.
- ENERGY STAR information for energy efficiency program planning (Dec 2025), ENERGY STAR (U.S. EPA). Accessed 2026-10-06.
- 10 CFR 430.32(d), energy conservation standards for water heaters (Tables 13 and 14), Legal Information Institute, Cornell Law School. Accessed 2026-10-06.
- ENERGY STAR certified water heaters (product finder), ENERGY STAR (U.S. EPA). Accessed 2026-10-06.
- Heat pump water heater rebate, Austin Energy. Accessed 2026-10-06.
- Rebates for your home, 2026 residential fact sheet, Nicor Gas. Accessed 2026-10-06.
- ComEd appliance rebates, ComEd. Accessed 2026-10-06.
- Energy efficient home improvement credit, Internal Revenue Service. Accessed 2026-10-06.
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