How to Choose a Water Heater

A water heater is the appliance you never think about — until it’s leaking on the basement floor at 6 a.m. and you’re buying under pressure. Choosing well before that day means the right fuel, the right size, and a unit that fits your space and your budget instead of whatever the emergency plumber has on the truck.

Tank vs. tankless vs. heat pump

There are three mainstream types, and the right one depends more on your house than on which is “best.” A conventional storage tank keeps 40–80 gallons hot and ready — simple, cheap to buy, easy to replace. A tankless (on-demand) unit heats water only as it flows, so you never run out, but flow rate is capped and cold-climate installs may need two units. A heat-pump or “hybrid” electric heater pulls heat from the surrounding air, cutting electric operating cost by more than half — but it needs roughly 700+ cubic feet of space and doesn’t love a freezing garage.

Tip: Don’t switch fuel types on a whim. Going from electric to gas means adding a gas line and venting; going from tank to tankless often means upsizing the gas line and adding a dedicated vent. Those add-ons can double an install — factor them in before the sticker price sells you.

Sizing: gallons, first-hour rating, and GPM

Undersize and you run out mid-shower; oversize and you pay to keep water hot you never use. For a tank, ignore the raw gallon number and look at the First Hour Rating (FHR) — how much hot water it can deliver in a busy hour. For tankless, the number that matters is gallons per minute (GPM) at your incoming water temperature.

• 1–2 people: 30–40 gal tank, or 6–7 GPM tankless
• 3–4 people: 40–50 gal tank, or 7–9 GPM tankless
• 5+ people: 50–80 gal tank, or 9–11 GPM tankless (or two units)

Northern homes with 40°F incoming water need a bigger tankless than the same house in Texas, because the heater has a larger temperature rise to cover. When in doubt, size up one step — the cost difference between a 40 and a 50 gallon tank is small; the cost of a cold shower is a return trip.

Fuel and efficiency: what you’ll actually pay to run it

The number on the yellow EnergyGuide sticker — the Uniform Energy Factor (UEF) — tells you how efficiently a unit turns fuel into hot water. Higher is better. A standard electric tank sits around 0.90 UEF; a heat-pump hybrid can hit 3.0+ because it moves heat rather than making it. Gas tanks run 0.60–0.70; condensing tankless models reach 0.90+.

Fuel price in your area usually decides gas vs. electric more than efficiency does. Where natural gas is cheap, a gas tank is hard to beat on operating cost and it keeps working in a power outage. Where electricity is reasonable, a heat-pump unit wins the long game. Rheem, A. O. Smith, and Bradford White dominate the tank market; Rinnai and Navien lead tankless — all sold through authorized retailer channels so your warranty is honored.

Don’t forget the install parts

The heater is half the job. A code-compliant swap needs the right connectors, valves, and safety gear — skip one and you fail inspection or void the warranty.

• Flexible gas or water connectors sized to the new unit’s inlets
• A new temperature & pressure (T&P) relief valve and discharge tube
• Dielectric unions or a dedicated shut-off valve on the cold inlet
• An expansion tank if you’re on a closed system with a backflow preventer
• A drip pan and sensor if the unit sits above a finished space
• Thread sealant — pipe dope or PTFE tape on every threaded joint

Tip: Buy the connectors and valves at the same time as the heater. Nothing stalls a Saturday install like realizing the old ¾″ connectors don’t reach the new tank’s ports.

Water quality: protect your investment

Hard water is the silent killer of water heaters — scale coats the tank bottom and heating elements, dropping efficiency and shortening life by years. If your area runs hard (over ~7 grains per gallon), a water softener pays for itself in heater longevity, and whole-home water filtration keeps sediment off the elements. On a tankless unit, annual descaling isn’t optional in hard-water regions — it’s the difference between 20 years and 8.

Pick by household

Frequently asked questions

Buy before the old one fails and you’ll choose on your terms, not the emergency plumber’s. Your local independent hardware store stocks the connectors, valves, and expertise to get it right the first time — and if you’re stuck between two units, ask us here.