10 C.F.R. § 431.110
Table 1 to § 431.110(a) -Commercial Water Heater Energy Conservation Standards
| Equipment | Size | Energy conservation standards a | |||
| Minimum thermal efficiency (equipment manufactured on and after October 9, 2015) (%) | Minimum thermal efficiency (equipment manufactured on and after October 6, 2026) (%) | Maximum standby loss (equipment manufactured on and after October 29, 2003) b | Maximum standby loss (equipment manufactured on and after October 6, 2026) b | ||
| Electric storage water heaters | All | N/A | N/A | 0.30 + 27/V m (%/h) | 0.30 + 27/V m (%/h) |
| Gas-fired storage water heaters and storage-type instantaneous water heaters | All | 80 | 95 | Q/800 + 110(V r )1/2 (Btu/h) | 0.86 * [Q/800 + 110(V r )1/2 ] (Btu/h) |
| Oil-fired storage water heaters | All | 80 | 80 | Q/800 + 110(V r )1/2 (Btu/h) | Q/800 + 110(V r )1/2 (Btu/h) |
| Electric instantaneous water heaters c | 10 gal [GREATER THAN EQUAL TO]10 gal | 80 77 | 80 77 | N/A 2.30 + 67/V m (%/h) | N/A 2.30 + 67/V m (%/h) |
| Gas-fired instantaneous water heaters and hot water supply boilers | 10 gal [GREATER THAN EQUAL TO]10 gal | 80 80 | 96 96 | N/A Q/800 + 110(V r )1/2 (Btu/h) | N/A Q/800 + 110(V r )1/2 (Btu/h) |
| Oil-fired instantaneous water heater and hot water supply boilers | 10 gal [GREATER THAN EQUAL TO]10 gal | 80 78 | 80 78 | N/A Q/800 + 110(V r )1/2 (Btu/h) | N/A Q/800 + 110(V r )1/2 (Btu/h) |
a V m is the measured storage volume, and V r is the rated storage volume, both in gallons. Q is the rated input in Btu/h, as determined pursuant to 10 CFR 429.44 .
b Water heaters and hot water supply boilers with a rated storage volume greater than 140 gallons need not meet the standby loss requirement if:
(1) The tank surface area is thermally insulated to R-12.5 or more, with the R-value as defined in § 431.102
(2) A standing pilot light is not used; and
(3) For gas-fired or oil-fired storage water heaters, they have a flue damper or fan-assisted combustion.
c The compliance date for energy conservation standards for electric instantaneous water heaters is January 1, 1994.
Table 2 to § 431.110(c) -Residential-Duty Commercial Water Heater Energy Conservation Standards
| Equipment | Specifications a | Draw pattern | Uniform energy factor b | |
| Equipment manufactured before October 6, 2026 | Equipment manufactured after October 6, 2026 | |||
| Gas-fired storage | 75 kBtu/hr and [LESS THAN EQUAL TO]105 kBtu/hr and [LESS THAN EQUAL TO]120 gal | Very Small Low Medium High | 0.2674-(0.0009 * V r ) 0.5362-(0.0012 * V r ) 0.6002-(0.0011 * V r ) 0.6597-(0.0009 * V r ) | 0.5374-(0.0009 * V r ) 0.8062-(0.0012 * V r ) 0.8702-(0.0011 * V r ) 0.9297-(0.0009 * V r ) |
| Oil-fired storage | 105 kBtu/hr and [LESS THAN EQUAL TO]140 kBtu/hr and [LESS THAN EQUAL TO]120 gal | Very Small Low Medium High | 0.2932-(0.0015 * V r ) 0.5596-(0.0018 * V r ) 0.6194-(0.0016 * V r ) 0.6470-(0.0013 * V r ) | 0.2932-(0.0015 * V r ) 0.5596-(0.0018 * V r ) 0.6194-(0.0016 * V r ) 0.6470-(0.0013 * V r ) |
| Electric instantaneous | 12 kW and [LESS THAN EQUAL TO]58.6 kW and [LESS THAN EQUAL TO]2 gal | Very Small Low Medium High | 0.80 0.80 0.80 0.80 | 0.80 0.80 0.80 0.80 |
a Additionally, to be classified as a residential-duty commercial water heater, a commercial water heater must meet the following conditions: (1) If the water heater requires electricity, it must use a single-phase external power supply; and (2) The water heater must not be designed to heat water to temperatures greater than 180 °F.
b V r is the rated storage volume (in gallons), as determined pursuant to 10 CFR 429.44 .
10 C.F.R. §431.110