They save energy by heating water only when needed, eliminating energy lost during standby operation.

Here’s how:

When a hot water tap is turned on in the home, cold water is drawn into the water heater. A flow sensor activates the gas burner, which warms the heat exchanger. Incoming cold water encircles the heat exchanger and leaves the heater at its set-point temperature. Combustion gases safely exit through a dedicated, sealed vent system.

By heating water only when needed, instead of maintaining a tank full of hot water at all times, tankless water heaters can achieve greater efficiency than standard tank-type water heaters.

ENERGY STAR qualified gas tankless water heaters provide hot water on demand, plus a whole lot more. Consider a qualified tankless water heater for your home and enjoy these benefits:

Save energy and money. You don’t use hot water 24-hours a day. Yet a standard tank-type water heater consumes energy round the clock to keep the water in its tank hot. By heating water only when you need it, ENERGY STAR qualified tankless water heaters save the typical family more than $100 per year on gas bills compared to a standard storage model. Larger families can save even more.

Continuous hot water. Tankless water heaters provide a continuous flow of hot water, so there’s no need to suffer through a cold shower if you’re the last one out of bed. Unlike with a conventional tank-type water heater, the hot water is always there when you need it.

Space-saving design. A qualified tankless model saves you an extra closet’s worth of space compared to a tank-type water heater. Gas tankless water heaters are small and wall-mounted, unlike bulky tank-type water heaters. An outdoor tankless water heater designed for outdoor installation frees up even more space and adds versatility to your basement, garage, or utility room.

Fewer worries. Tankless water heaters have a life expectancy of 20 years, much longer than any conventional tank-type water heater. And with a tankless model, the risk of tank leaks and water damage is a thing of the past.

Source: ENERGY STAR

Hi Mike,

Every professional plumber will have their favorite product and you should too!

Let me give you (and my readers) some information on both Pex and CPVC so that you can better reach an educated decision.

Pex is a water supply piping system that doesn’t corrode or develop pinhole leaks, is chlorine-resistant, scale-resistant, and has fewer fittings, connections, and elbows than rigid plastic and metallic pipe

(Pex)
PEX pipe is approved for potable hot- and cold-water plumbing systems and hot-water (hydronic) heating systems in all model plumbing and mechanical codes across the U.S. and Canada. PEX piping systems are durable, provide security for safe drinking water, and use reliable connections and fittings. There are currently about ten domestic producers of quality PEX piping.

Brass fittings and couplings and polyethylene tees and elbows are available. Fittings are available in both mechanical compression and crimping styles, depending on application and manufacturer. In addition to domestic water supply systems, PEX tubing can be used for floor or wall radiant heating, and snow and ice melting systems in sidewalks and driveways.

PEX tubing is light weight, and it can withstand operating temperatures of up to 200° F (93° C). It is flexible and can easily be bent around corners and obstacles, and through floor systems. Sizes of PEX tubing range from 3/8-inch to over 2 inches.

Note: PEX tubing should not connect directly to a hot water tank or solar water heater where the temperature of the water could exceed 200° F. Fittings and connections must be installed with special calibrated tools by a trained plumber.The pipe should not be used in installations subject to continual ultraviolet light exposure.
Source: NAHB Research Center

Chlorinated polyvinyl chloride (CPVC) is a thermoplastic pipe and fitting material approved for potable water distribution in all fifty states. It is an off-white rigid material and installs using fittings made from the same material bonded in place with a solvent.

(CPVC)
CPVC has been used successfully in residential, commercial, and industrial applications for nearly 50 years. It is most commonly used in single-family and multi-family hot and cold water distribution systems. However, it can be used for residential fire sprinkler systems, chemical drain waste systems, and industrial processing. CPVC key advantages include its resistance to corrosion, pitting, and scaling, ease of installation, and light weight.

Though PVC and CPVC belong to the plastics family and possess similar core materials, they perform very differently. The chlorination process used in making CPVC gives the material its superior performance in both high temperature and high pressure applications. The extra chlorine molecule makes CPVC very difficult to burn. CPVC will not sustain a flame on its own as there is not enough oxygen in the atmosphere to make it burn. When the flame source is removed, CPVC will self-extinguish. Additionally, CPVC should not be confused with polybutylene piping, which suffers from reliability issues because it could react unfavorably to some elements in various water systems.

CPVC piping offers a rigid piping system that many builders and plumbers are accustomed to without the risks of corrosion, pitting, scaling, and pinhole leaks that can occur in copper installations when local water or soil conditions are less than favorable.

CPVC pipe is generally cheaper than copper piping as well. Its cost, ease of workability and its durability make it an economical choice. CPVC piping is also an energy efficient choice, since less heat is lost as hot water moves through the pipes. It can be a quieter option for homeowners as well, as the structure may reduce water hammer.

Note: When connecting CPVC to a gas water heater, use at least six inches of metal pipe or appliance connector so that the CPVC tubing is not damaged by build-up of excessive heat from the draft diverter. Some high-efficiency direct-vent gas water heaters eliminate the radiant heat from the flue and can be piped directly to the water heater. CPVC can be piped directly to an electric water heater.
Source: NAHB Research Center

(Copper)

Well Mike, Sorry, but I “copped out” on you. I didn’t choose either one…I’ve always had an affinity for copper.
Carl