Water Heater Key Product Criteria

A non-solar water heater can be certified as ENERGY STAR by meeting Uniform Energy Factor (UEF) criteria.

Solar water heaters must meet minimum Solar Uniform Energy Factor (SUEF) criteria to be certified as ENERGY STAR.

ENERGY STAR Residential Water Heaters — Eligible Product Types
Storage Water Heaters Storage type units designed to heat and store water at a thermostatically controlled temperature, including: gas storage water heaters with a nominal input of 75,000 British thermal units (Btu) per hour or less, containing more than one gallon of water per 4,000 Btu per hour of input; electric heat pump water heaters with a maximum current rating of 24 amperes at an input voltage 250 volts or less, including all ancillary equipment such as fans, storage tanks, pumps, or controls necessary for the device to perform its function.1
Instantaneous Water Heaters Instantaneous (or “tankless”) type units heat water, but contain no more than one gallon of water per 4,000 Btu per hour of input with an input less than 200,000 Btu per hour for gas-fired instantaneous.2
Solar Water Heaters Solar water heaters include a collector and storage tank, and use the sun’s energy to heat water using one of the five basic types of solar water heating systems:
  1. forced circulation (includes both direct and indirect systems),
  2. integrated collector and storage,
  3. thermosiphon,
  4. self-pumped, or
  5. photovoltaic (PV).
High Capacity Storage Water Heaters Gas-fired storage residential-duty commercial water heaters include gas-fired storage water heaters that are designed to deliver hot water at a temperature less than or equal to 180°F, with an input rate greater than 75,000 Btu per hour and not exceeding 105,000 Btu per hour, containing more than one gallon of water per 4,000 Btu per hour of input, and storage volume less than or equal to 120 gallons. For models requiring electricity, a single-phase external power supply is used. 2

ENERGY STAR Criteria – Uniform Energy Factor

Criteria for Certified Electric Storage Water Heaters

Criteria ENERGY STAR Requirements
Uniform Energy Factor Integrated HPWH UEF ≥ 3.30

Integrated HPWH,

120 Volt / 15 Amp Circuit
UEF ≥ 2.20
Split System HPWH UEF ≥ 2.20
First Hour Rating FHR ≥ 45 gallons per hour
Warranty Warranty ≥ 6 years on sealed system
Safety UL 174 and UL1995 or UL 60335-2-40
Lower Compressor Cut-Off Temperature (Reporting Requirement Only) Report ambient temperature (°F) below which the compressor cuts off and electric resistance only operation begins

Criteria for Certified Gas-fired Storage Water Heaters

Criteria ENERGY STAR Requirements
Uniform Energy Factor ≤ 55 gallons Medium Draw Pattern UEF ≥ 0.64 (Effective April 18, 2023 UEF ≥ 0.81) 

High Draw Pattern UEF ≥ 0.68 (Effective April 18, 2023 UEF ≥ 0.86)
> 55 gallons Medium Draw Pattern UEF ≥ 0.78 (Effective April 18, 2023 UEF ≥ 0.86)

High Draw Pattern UEF ≥ 0.80 (Effective April 18, 2023 UEF ≥ 0.86)
First Hour Rating FHR ≥ 51 gallons per hour
Warranty Warranty ≥ 6 years on system (including parts)
Safety ANSI Z21.10.1/CSA 4.1

Criteria for Certified Gas-fired Instantaneous Water Heaters

Criteria ENERGY STAR Requirements
Uniform Energy Factor UEF ≥ 0.87 (Effective April 18, 2023 UEF ≥ 0.95)
Maximum Gallons Per Minute Max GPM ≥ 2.9 over a 67° rise
Warranty Warranty ≥ 6 years on heat exchanger and ≥ 5 years on parts
Safety ANSI Z21.10.3/CSA 4.3

Criteria for Certified Gas-fired Storage Residential-duty Commercial Gas Water Heaters

Criteria ENERGY STAR Requirements
Uniform Energy Factor UEF ≥ 0.80 (Effective April 18, 2023 UEF ≥ 0.86) 
Warranty Warranty ≥ 6 years on system
Safety ANSI Z21.10.3/CSA 4.3

ENERGY STAR Criteria – Solar Energy Factor

Solar water heater models must meet all of the identified criteria to be labeled as ENERGY STAR.

Criteria for Certified Solar Water Heaters

Criteria ENERGY STAR Requirements
Solar Uniform Energy Factor SUEF ≥ 3.00 for electric backup
SUEF ≥ 1.80 for gas backup
Warranty ≥ 10 years on collector
≥ 6 years sealed system
≥ 2 years on controls
≥ 1 year on parts


Glossary

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. The FHR is measured at a 125°F outlet temperature in the Uniform Energy Factor test method.

Gallons per Minute (GPM): The amount of gallons per minute of hot water that can be supplied by an instantaneous water heater while maintaining a nominal temperature rise during steady state operation. The GPM is measured over a 67°F temperature rise in the Uniform Energy Factor test method.

Solar Uniform Energy Factor (SUEF): The energy delivered by the total system divided by the electrical or gas energy put into the system.

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


1 10 CFR Part 430, Subpart B, Appendix E

2 10 CFR Part 430, Subpart B, Appendix E and 10 CFR Part 430, Subpart A, § 430.2 Definitions