BTU Rates in Water Heaters

30,000 BTUs

• A gas storage water heater (the conventional “tallboy” cylindrical tower) that is anywhere in the 30,000 BTU range will provide enough hot water comfortably for a single person or couple who live in a one-bedroom apartment. Most water heaters in the 30,000 BTU range will have a tank size of 29 to 34 gallons. They also will have a gallons per minute (GPM) rating around 0.60 and gallons per hour (GPH) rating of around 36.5.

40,000 BTUs

• A conventional water heater that has a 40,000 BTU capacity will provide enough hot water comfortably for up to three people who live in a two bedroom home. Water heater tank sizes typically will range around 40 gallons, at about a ratio of 1 gallon per 1,000 BTUs. The water heaters generally will have a similar GPH ratio of around 40 gallons per hour.

50,000 BTUs

• Conventional gas storage water heaters in the 50,000 BTU range are not too far apart from those with a 40,000 BTU capacity. A 50,000 BTU water heater with a 50 or 60-gallon tank will accommodate comfortably a family of four, who live in a home with three or four bedrooms and with two or three bathrooms. The typical GPH range for a 50,000 BTU water heater 38.4 to 41.

High Efficiency Tankless Gas Water Heaters

• The BTU capacity rises dramatically with tankless water heaters. Unlike conventional storage tank water heaters, they do not hold water (hence the term “tankless”). Tankless water heaters have the highest BTU capacity, starting at around 150,000 BTUs for residential models. Most of these models also qualify for rebates and credits under the Energy Star program, which requires a 75,000 BTU minimum as of September 10, 2010. A 199,000 BTU capacity tankless gas water heater can accommodate easily a 3-bathroom home, and has a GPM of 9.5.

BTU Considerations

• It also is important to note the GPM, GPH and first hour rating (FHR) numbers and ratings when shopping in addition to the BTU capacity. The FHR tells you how much hot water the unit can supply at peak usage, such as early morning shower time for multiple people in the household. Start with a base BTU capacity, such as 40,000 BTUs, and select several models that have this capacity. Then compare the GPM, GPH and FHR ratings to make your choice. As a rule, the higher each number and rating, the more efficient the unit will be at producing hot water when everyone in your household needs it.