What Size Water Heater Do I Need?

The number that matters is peak simultaneous demand — how much hot water the house needs during its busiest hour, not across a day. A shower running while the dishwasher fills is the kind of moment that decides whether a tank is big enough.

Then recovery rate: how fast the unit reheats once it is drawn down. A gas heater recovers considerably faster than an electric one of the same capacity, which means a smaller gas tank can serve a house that would need a larger electric one.

An oversized tank keeps more water hot than the house will use, and pays for that in standby loss every hour of every day. It also costs more up front and takes more space in a closet that usually does not have any spare.

The honest answer is that most houses land in a fairly narrow band, and the sizing conversation is about the handful that do not — the large family, the soaking tub, the home with a hot tub feed or an unusual fixture count.

We ask how many people, how many bathrooms, and what the worst morning looks like. Then we look at the space, the fuel, and the existing connections, because a tank that will not fit through the closet door is not a recommendation.

If the old unit was genuinely the wrong size, we say so and explain why, rather than quietly fitting the same thing again.