GallonGauge — Gallons, first-hour rating and GPM — the three numbers that decide it.

1
First Hour Rating — The Number That Actually Sizes a Water Heater
A 40-gallon gas heater delivers more hot water in an hour than a 50-gallon electric one, and the label says so.
3 min read
2
Heat Pump Water Heaters — Three Times the Efficiency, With Conditions
The efficiency is not marginal — it is a factor of three — and the constraints are real and physical.
3 min read
3
Sizing a Tankless Heater — GPM at Your Temperature Rise
The box says 9.8 gallons per minute. That is at a temperature rise nobody in a cold climate ever asks for.
3 min read
4
Expansion Tanks — Why a Closed System Needs One
The relief valve dripping is not a faulty valve. It is the valve doing its job because nothing else is.
3 min read

Water heater replacement cost by city