Dear Jim: If I take the final shower in the morning, there is not much hot water left (brrr!). Will installing an instantaneous water heater provide more hot water in the morning as well as lower my utility bills? – Ed P.

Dear Ed: Installing a whole-house or point-of-use instantaneous (also called tankless) water heater will accomplish both your goals. One water heater can provide enough hot water for 100 or more consecutive showers. For a family of four, an annual utility bill savings of $100 is common.

Instantaneous water heaters can use natural gas, propane or electricity, although propane and gas models provide the greatest hot water output.

Many of the newer models have power vents so no chimney is needed. This makes them ideal for switching from electricity to gas or propane heat.

These water heaters have an Energy Factor (EF) as high as .84 as compared to the best tank-type water heaters at an EF of about .64. By not having to keep a big tank of water hot, the standby heat losses are minimal. This also eliminates a double energy loss when air-conditioning in the summer.

Even whole-house-size instantaneous water heaters are tiny by tank-type standards. If you saw one, you would not believe it could provide all the hot water for your family. Some whole-house gas models weigh only 60 pounds and hang on a wall in a closet. They take up only 2 cubic feet of space.

Instantaneous water heaters often cost more initially than tank-type ones, but with no tank to rust, they last a long time and can be repaired instead of trashed.

These water heaters work by heating the water instantly as it passes through the water heater. When you turn on the hot water faucet, the water heater senses the flow and pressure change. Instantly, gas burners or electric heating elements come on. Close the faucet and the burners stop immediately.

Some older instantaneous water heater designs allowed the water temperature to vary depending on how much water was being used. The newer ones have modulating gas valves or sequential electric elements. The amount of heat produced depends on the water flow rate for a steady water temperature.

Some tiny instantaneous point-of-use (under a bathroom sink) models have precise temperature control with a wall-mounted digital readout. The sensor checks the water temperature 7,200 times each minute to keep it steady.

Although an instantaneous water heater can provide endless hot water, its maximum flow rate is limited to its heating capacity. This means you may not have enough hot water to take two showers and run the clothes and dishwasher simultaneously. You should run those late at night anyway.

Write for (instantly download -www.dulley.com) Update Bulletin No. 431- buyer’s guide of 14 manufacturers (40 models) of gas and electric instantaneous water heaters listing heat outputs, flow rates (gpm), comfort and efficiency features and typical prices. Please include $3 and a business-size SASE. Send to James Dulley, 6906 Royalgreen Drive, Cincinnati, OH 45244.