Energy Star Water Heaters: What 1,261 Certified Models Show About Efficiency
The short answer
There are 1,261 Energy Star certified residential water heaters, 601 of them heat pump models, according to EPA’s Energy Star certified products data. The median heat pump water heater has a Uniform Energy Factor of 3.68, against 0.95 for certified gas tankless and 0.90 for certified gas storage units, and uses a median 1,181 kWh a year under the federal test. 72 certified heat pump models now plug into a standard 120-volt outlet.
Where the index stands
Energy Star publishes the full list of certified water heaters as open data, with the test results manufacturers submit: Uniform Energy Factor (UEF, the federal efficiency metric), annual energy use, tank size, first-hour rating, refrigerant, noise and smart-grid features. Read as a whole, the list shows what the efficient end of the market now looks like. This report counts models; it does not rank brands.
| Certified type | Models | Median UEF | UEF range |
|---|---|---|---|
| Hybrid/Electric Heat Pump | 601 | 3.68 | 2.52 to 4.50 |
| Gas Tankless | 463 | 0.95 | 0.95 to 0.98 |
| Gas Storage | 71 | 0.90 | 0.86 to 0.90 |
| Gas-fired Storage Residential-duty Commercial | 71 | 0.88 | 0.86 to 0.93 |
| Solar with Electric Backup | 30 | n/a | n/a |
| Solar with Gas Backup | 25 | n/a | n/a |
Source: EPA Energy Star certified residential water heaters dataset (data.energystar.gov, pbpq-swnu), retrieved 4 October 2026. Solar water heaters are rated on a different metric and show n/a.
The underlying series, sourced
- Certified models: 1,261; heat pump 601, gas tankless 463, gas storage 71, residential-duty commercial gas storage 71, solar 55. Source: Energy Star.
- Heat pump UEF: median 3.68, range 2.52 to 4.50. Source: Energy Star.
- Heat pump annual electricity use under the DOE test: median 1,181 kWh, range 643 to 1,741. Source: Energy Star.
- Gas tankless annual gas use: median 178 therms. Source: Energy Star.
- Heat pump refrigerants: R-134a 441, R-744 (CO2) 99, R-513A 31, R-1234YF 28 models. Source: Energy Star.
- Heat pump models with connected (smart-grid) capability: 280 of 601. Source: Energy Star.
- Heat pump models by tank size: Under 50 gal 259, 70 to 79 gal 127, 50 to 69 gal 152, 80 gal or more 63. Source: calculated from Energy Star.
- Median sound pressure of heat pump units: 49 dBA where reported. Source: Energy Star.
Reading the series
| Heat pump tank size | Models | Median UEF |
|---|---|---|
| Under 50 gal | 259 | 3.52 |
| 50 to 69 gal | 152 | 3.70 |
| 70 to 79 gal | 127 | 4.00 |
| 80 gal or more | 63 | 3.45 |
How the index is constructed
Heat pumps are about four times as efficient on paper
Formula. Median UEF of certified heat pump models against certified gas tankless models.
Calculation. 3.68 / 0.95 = 3.9.
Finding. A UEF above 1 is possible for heat pumps because they move heat from the air rather than generating it. UEF compares delivered hot water to site energy; it does not account for the different cost or emissions of electricity and gas, so running cost depends on local prices.
Limitations. UEF is a laboratory rating under the DOE test procedure; real-world performance varies with the temperature of the space where the unit sits.
The 120-volt plug-in category is real but small
Formula. Share of certified heat pump models that are 120-volt integrated units.
Calculation. 72 of 601 = 12.0 percent; median UEF 3.00.
Finding. Plug-in heat pump water heaters remove the need for a new 240-volt circuit in many replacements, which is the main barrier when swapping out a gas heater. They are now a certified category with dozens of models, though most certified heat pumps still need 240 volts.
Limitations. Model counts measure availability, not sales.
The number to quote
- 601 Energy Star certified heat pump water heater models; median UEF 3.68.
- Certified gas tankless median UEF: 0.95.
- 72 certified 120-volt plug-in heat pump models.
Download the data
Model counts, UEF medians and ranges, annual electricity and gas use. Published under a Creative Commons Attribution 4.0 licence. Attribution: The Plumbing Brief.
Energy Star certified water heaters: summary by type (CSV)
How this report was built
Methodology
Source. US EPA Energy Star, certified residential water heaters dataset (Socrata ID pbpq-swnu), all 1,261 records, retrieved 4 October 2026.
Derived figures. Counts, medians and ranges by The Plumbing Brief. Brands are not ranked.
Retrieval date. 4 October 2026.
Data limitations
- The list covers certified models only, not the whole market or what is installed in homes.
- A model count is not a sales measure; one popular model may outsell dozens.
- Certification dates largely reflect recertification after Energy Star specification updates and are not used as an adoption trend.
- For what is actually installed, see our water heaters by state report (EIA).
Source quality ranking
Tier 1. US EPA Energy Star certified products data (manufacturer-submitted, third-party certified).
Tier 2. None used. Tier 3. None used.
Briefing note
EPA’s Energy Star program lists 1,261 certified residential water heaters, including 601 heat pump models with a median Uniform Energy Factor of 3.68 against 0.95 for certified gas tankless units, according to an analysis of the certified products data by The Plumbing Brief. 72 of the heat pump models plug into a standard 120-volt outlet, and 99 use CO2 as their refrigerant.
Story angles
- What the most efficient water heaters on the market look like
- Plug-in heat pump water heaters arrive
- Heat pump vs gas tankless: the efficiency ratings compared
- CO2 refrigerant heat pump water heaters
Common questions about the index
What is the most efficient type of water heater? Heat pump water heaters: certified models have a median UEF of 3.68, against 0.95 for certified gas tankless.
How much electricity does a heat pump water heater use? A median 1,181 kWh a year under the federal test procedure for certified models.
Are there 120-volt heat pump water heaters? Yes. 72 certified models plug into a standard outlet.
How many Energy Star water heaters are there? 1,261 certified models.
What is UEF? Uniform Energy Factor, the federal efficiency rating for water heaters: delivered hot water energy divided by energy used under a standard test.
How to cite this report
The Plumbing Brief, “Energy Star Water Heaters: What 1,261 Certified Models Show About Efficiency”, https://theplumbingbrief.com/energy-star-water-heaters/, accessed [date].
Last reviewed: 2026-10-04.
