10 CFR § 431.110 - Energy conservation standards and their effective dates.

§ 431.110 Energy conservation standards and their effective dates.

(a) Each commercial storage water heater, instantaneous water heater, and hot water supply boiler (excluding residential-duty commercial water heaters) must meet the applicable energy conservation standard level(s) as specified in the table to this paragraph. Any packaged boiler that provides service water that meets the definition of “commercial packaged boiler” in subpart E of this part, but does not meet the definition of “hot water supply boiler” in subpart G of this part, must meet the requirements that apply to it under subpart E of this part.

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/Vm (%/h) 0.30 + 27/Vm (%/h)
Gas-fired storage water heaters and storage-type instantaneous water heaters All 80 95 Q/800 + 110(Vr) 1/2 (Btu/h) 0.86 × [Q/800 + 110(Vr) 1/2] (Btu/h)
Oil-fired storage water heaters All 80 80 Q/800 + 110(Vr) 1/2 (Btu/h) Q/800 + 110(Vr) 1/2 (Btu/h)
Electric instantaneous water heaters c <10 gal
≥10 gal		 80
77		 80
77		 N/A
2.30 + 67/Vm (%/h)		 N/A
2.30 + 67/Vm (%/h)
Gas-fired instantaneous water heaters and hot water supply boilers <10 gal
≥10 gal		 80
80		 96
96		 N/A
Q/800 + 110(Vr) 1/2 (Btu/h)		 N/A
Q/800 + 110(Vr) 1/2 (Btu/h)
Oil-fired instantaneous water heater and hot water supply boilers <10 gal
≥10 gal		 80
78		 80
78		 N/A
Q/800 + 110(Vr) 1/2 (Btu/h)		 N/A
Q/800 + 110(Vr) 1/2 (Btu/h)

a Vm is the measured storage volume, and Vr 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.

(b) Each unfired hot water storage tank manufactured on and after October 29, 2003, must have a minimum thermal insulation of R–12.5.

(c) Each residential-duty commercial water heater must meet the applicable energy conservation standard level(s) as follows:

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 ≤105 kBtu/hr and ≤120 gal Very Small
Low
Medium
High		 0.2674−(0.0009 × Vr)
0.5362−(0.0012 × Vr)
0.6002−(0.0011 × Vr)
0.6597−(0.0009 × Vr)		 0.5374−(0.0009 × Vr)
0.8062−(0.0012 × Vr)
0.8702−(0.0011 × Vr)
0.9297−(0.0009 × Vr)
Oil-fired storage >105 kBtu/hr and ≤140 kBtu/hr and ≤120 gal Very Small
Low
Medium
High		 0.2932−(0.0015 × Vr)
0.5596−(0.0018 × Vr)
0.6194−(0.0016 × Vr)
0.6470−(0.0013 × Vr)		 0.2932−(0.0015 × Vr)
0.5596−(0.0018 × Vr)
0.6194−(0.0016 × Vr)
0.6470−(0.0013 × Vr)
Electric instantaneous >12 kW and ≤58.6 kW and ≤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 Vr is the rated storage volume (in gallons), as determined pursuant to 10 CFR 429.44.

[88 FR 69822, Oct. 6, 2023]