Gas tankless water heaters are able to produce a larger temperature rise per gpm than electric models. Most demand water heaters are rated for a variety of inlet temperatures. Typically, a 70°F water temperature rise is possible at a flow rate of 5 gallons per minute through gas-fired demand water heaters and 2 gallons per minute through electric water heaters. Faster flow rates or cooler inlet temperatures can sometimes reduce the water temperature at the most distant faucet.
Examples:
FIXTURE
AVERAGE FLOW GPM
AVERAGE TEMP.
Tub4.0 GPM102°F Shower2.5 – 3.0 GPM104°F Washing Machine2.0 GPM120°F Dishwasher1.5 GPM110°F Kitchen Sink1.5 GPM110°F