Planners

Pick a tankless water heater or enter its kW or BTU rating to see the amps it draws at 240 or 208 volts, the breakers its maker calls for, and the gas a line must deliver per hour.

Add up your household's busiest hour of hot water with AHRI's per-use figures to get the first-hour rating a heat pump water heater needs.

Count the showers, sinks and appliances that run at once, set your winter inlet water, and see the flow your tankless heater must hold and every gas and electric unit that keeps up.