The conventional storage tank water heater remains the volume residential water heater across the US — roughly 75% of all installs. A tank water heater stores 30–80 gallons of preheated water in an insulated steel tank, fired by gas atmospheric burner, gas power-vent, gas direct-vent, or electric resistance elements. Compared to tankless, storage tanks have lower upfront cost, simpler install (no gas-line resizing, no PVC venting), and tolerate higher peak demand events without GPM limits. The trade-off is standby losses (continuous reheating to maintain temperature) and a finite reservoir.

Tank water heater by fuel type

Gas tank — atmospheric chimney venting, lowest install cost, lowest operating cost where natural gas is available. Examples: Rheem Performance Platinum 50G, AO Smith Signature Premier 50G, Bradford White Defender 50G.
Power-vent gas tank — PVC venting eliminates chimney requirement. Right pick for closet and manufactured-home installs. Rheem Performance Power Vent 50G.
Direct-vent gas tank — sealed combustion 2-pipe vent for code-required tight-envelope installs. Rheem Performance Plus 50G Direct Vent, AO Smith Vertex.
Electric tank — 240V dual-element. Required where natural gas isn't available. Volume picks: Rheem Performance Platinum 50G Electric, AO Smith Signature 100 50G Electric.
Heat pump (hybrid) tank — refrigerant-cycle technology, one-third the operating cost of resistance electric. Rheem ProTerra 50G, AO Smith Voltex 50G.

Capacity sizing

30 gallon — 1–2 person households, ADUs, vacation cabins
40 gallon — 2–3 person households (volume size)
50 gallon — 3–4 person households (the most-shopped size)
75 gallon — 5–7 person households or homes with hot-tub fill demand
80 gallon — high-capacity electric for 4–6 person households
100 gallon — light-commercial and estate-class residential

Tank water heater brands

The volume residential tank brands in the US are Rheem, AO Smith, and Bradford White. Each has 6/9/12-year warranty tiers and overlapping lineups:

Rheem — Performance / Performance Plus / Performance Platinum (big-box at Home Depot) plus the contractor-channel Professional Classic Plus. See the full Performance Platinum line.
AO Smith — Signature / Signature Premier (Lowe's primary channel) plus ProLine for plumber channel.
Bradford White — Defender / Eco-Defender / ICON System (plumber channel only). Build-quality reputation is strong.

Specialty tank options:

Rheem Marathon — limited-lifetime polybutene tank. The only US residential water heater whose tank doesn't corrode.
Light-commercial high-capacity: AO Smith Cyclone 100G.

Standby loss and operating economics

Tank water heaters' main efficiency hit is "standby loss" — heat radiating through the tank wall while idle. Modern Energy Star tanks have ~0.7 UEF (gas) and 0.93 UEF (electric), capturing most of the energy delivered to the burner or element. Heat pump tanks (ProTerra, Voltex) hit 3.45+ UEF by extracting heat from the ambient air rather than generating it. Condensing gas tanks hit 0.84+ UEF by recovering heat from flue gases — the highest non-heat-pump efficiency available.

Bottom line on tank water heaters

Tank water heaters remain the right pick for: most residential replacements where like-for-like swap minimizes install cost, households without 3/4" gas line capacity or PVC venting routes, short ownership horizons where tankless upfront premium doesn't pay back, and high simultaneous demand events (tub fills) that exceed tankless GPM limits. For long-horizon owners on natural gas, condensing tankless wins on lifetime operating cost; for long-horizon owners on electric, heat pump wins. The full tank lineup spans every brand and capacity in our catalog above.