Faster flow rates or cooler inlet temperatures will reduce the water temperature at the most distant faucet. Some types of tankless water heaters are thermostatically controlled. They can vary their output temperature according to the water flow rate and the inlet water temperature. This is useful when using a solar water heater for preheating the inlet water. If, using the above example, you connect this same unit to the outlet of a solar system, it only has to raise the water temperature a few degrees more, if at all, depending on the amount of solar gain that day.
Contents Cost Demand water heaters generally cost more than conventional storage tank-type units.
The appeal of tankless water heaters is not only the elimination of the standby losses and the resulting lower operating costs, but also the fact that the heater delivers hot water continuously. Ask the manufacturer of the unit how much gas the pilot light uses for the models you consider. It is a common practice in Europe to turn off the pilot light when the unit is not in use. This resembles the spark ignition device on some gas kitchen ranges and ovens. Not all demand water heaters have this electrical device.