Bradford White RG2F40S6N (40 gal) vs RG2F50S6N (50 gal) fan-assist tanks

The input is identical at 38,000 BTU/h, so recovery is identical at about 41 US gal/h (155 L/h) at a 50 °C rise. That is why the first-hour figures are nearly the same, 284 L against 288 L, a difference of about one US gallon. The 50-gallon tank's real advantage is stored volume for a single large draw such as a soaker tub; its recovery between draws is no faster than the 40-gallon model's.

In this family the smaller tank is also the more efficient one: UEF 0.70 for the 40-gallon against 0.68 for the 50-gallon under the same medium-draw test, the standby penalty of more surface area per unit of stored volume. Both are below ENERGY STAR's 0.81 threshold for the size, and neither UEF should be read against a legacy EF or a tankless UEF measured under a different draw pattern.

Fan assist is the reason to be in this family at all. Exhaust still leaves through a 3 in or 4 in draft diverter into a chimney or B-vent, but a high-efficiency blower pulls the gases through a restricted baffle, which is what lifts the family above the plain atmospheric line's efficiency and lets it work with a marginal chimney. The trade is a 120 VAC receptacle for the blower and ICON control, so hot water stops when the power does, and a blower the plain atmospheric tanks do not have.

Dimensions decide fit as much as capacity. The 40-gallon model stands 47 in (1194 mm) to the top of the heater in a 22 in jacket and ships at 150 lb; the 50-gallon model stands 48 in (1219 mm) in a 24 in jacket and ships at 176 lb, so a tight doorway or a narrow closet can settle the choice. Both are Defender FVIR tanks with a magnesium anode, both carry a 6-year tank and parts warranty with no labour, and both need the anode inspected every two years.