What we found on the Internet about instant hot water

Following a reader's query (see Readers Letters) we found the following on the Internet.

Advantages to on-demand water heating include: 

Tankless water heaters are compact in size, taking up less space than conventional tank type water heaters.

They can virtually eliminate standby losses - energy wasted when hot water cools down in long pipe runs or while it's sitting in the storage tank.

By providing hot water immediately where it's used, tankless water heaters waste less water. You don't need to let the water run as you wait for hot water to reach a remote faucet.

A tankless water heater can provide unlimited hot water as long as it is operating within its capacity.

Expected life of tankless water heaters is 20 years, compared to 10 to 15 years for tank type water heaters.

Disadvantages include:

Tankless water heaters usually can't supply enough hot water for simultaneous uses such as showers and laundry.

Unless the system is equipped with a modulating temperature control, it may not heat water to a constant temperature at different flow rates. That means that water temperatures can fluctuate uncomfortably - particularly if the water pressure varies in different parts of the house.

Electric tankless water heaters require a relatively high electric power draw because water must be heated quickly to the desired temperature. In some cases the home's electric service may need to be upgraded.

Tankless gas water heaters must be vented to the outdoors, either with a direct vent or conventional exhaust flue.

If a gas-powered unit has a pilot light, it can waste energy (with a conventional water heater, the pilot heats the water in the tank so it isn't really wasted).