Marietta Water Heater Sizing Guide

Quick rundown

For tanks: a 1-bath home runs on 30 gallons. A 1.5-bath home wants 40. A 2-bath wants 50. A 3-bath wants 75. For tankless, you size by GPM and BTU. Most quick calculators forget Georgia winter inlet temps, which matters more than people think.

Tank sizing by household

• 1-2 people, 1 bath: 30 to 40 gallon
• 2-3 people, 1.5 baths: 40 to 50 gallon
• 3-4 people, 2 baths: 50 gallon gas or 65 gallon electric
• 4-5 people, 2.5+ baths: 65 to 75 gallon
• 5+ people, 3+ baths: 75 to 80 gallon, or two 50s in series

Why Marietta inlet temps matter

Most tankless sizing tools assume 70 degree inlet water. In Marietta, January groundwater drops to 50 to 55 degrees. That changes the math. The unit now has to raise the water 65 to 70 degrees to hit a 120 degree shower, not 50. The advertised GPM drops by about 25 percent in winter.

Tankless BTU sizing in Marietta

For most 2-bath Marietta homes, especially in East Cobb or Smyrna, you want a 199,000 BTU condensing unit (Rinnai RU199e, Navien NPE-240A2, Rheem RTGH-95). Smaller 160K models can deliver cold mid-shower in January. For 3+ bath homes, run two units in parallel or step up to a 240K commercial-grade unit. Older homes near the Marietta Square sometimes need a gas line upsize first.

Recovery rate, not just tank size

A 50 gallon gas tank with a 40,000 BTU burner recovers about 40 gallons per hour. The same tank with a 50,000 BTU burner recovers 50. More BTU means less waiting between showers. For Marietta homes near Kennesaw State or active families in East Cobb running back-to-back showers, prioritize recovery rate, not raw tank gallons.