Two water heaters that look alike on a showroom floor can ask very different things of a house. Before you compare brands or prices, settle what the house can supply and what the household uses. Then compare the paper each seller gives you.

A conventional tank holds a stored supply of hot water and heats it back up when the level drops. Look at the tank capacity and the recovery rate on the maker's sheet, and ask how quickly the tank refills after a long shower. A tankless unit heats water as it flows. Look at the flow rating it lists at the temperature rise you need, and check whether your gas line or electrical supply can carry the unit at full load. Tankless units often need a venting path and sometimes a larger gas line. Those needs decide the install more than the unit does.

Read the yellow energy label on any new unit. It shows the rating the maker certifies under the standard test. Compare it between units of the same type and fuel, not across types. Note the fuel and whether the unit runs on gas or electricity.

Read the warranty paper on its own. A manufacturer warranty covers parts under the conditions the maker writes, which often include registration, a maintenance step, and a specific installer setup. It does not cover the installer's labor unless the installer provides that separately. Write down the warranty term for the tank and for any parts, and the conditions attached to each.

  • Fuel type, and whether the house supply matches it
  • Tank capacity or flow rating, stated in the maker's units
  • Recovery time or temperature-rise flow, as the maker states it
  • Yellow energy label rating, compared only within the same type
  • Warranty term for the tank and for parts, and the conditions attached
  • Venting, gas line, expansion tank, drain pan, and permit, each listed on the quote

When two sellers quote the same unit, lay their quotes next to each other line by line. Confirm that both include the same venting, the same connector, the same expansion tank, the same haul-away of the old unit, and the same permit handling. Ask each seller to write down what is excluded. The paper that matches the house and the paper that matches the warranty are the two you need before you choose.