Point of use water heaters - serving a single faucet, sink, or shower-room... - make sense from an energy savings standpoint.
They are a fast and effective way of getting hot water instantly, without water and energy waste. They are especially useful in hot climates.
Point of use water heaters can replace central water heaters in homes with relatively small hot water needs, in hot climates (though not in other cold or moderate climates).
With a point-of use water heater the water is heated near the sink, bath or shower where the water is used.
Tthey can also be used to boost the temperature of water at remote fixtures, that is, fixtures that are a long way from a central water heater.
Climate, Uses and Limitations of point-of-Use water heaters
In hot climates, where water temperature is higher (say, average incoming cold water temperatures between 70°F/21ºC and 80°F/27ºC.), and where the residential hot water needs are small or moderate, point-of-use water heaters can be highly advantageous.
Most existing units provide a temperature rise between 10º and 30ºF/6ºC-17ºC, which is often enough in these climates.
Although they may also be advantageous in other climates for small hot-water heating needs, you should be aware of their limitations.
Quality 220-volt models can increase the temperature of the water from 40ºF/4ºC up to, say, 120º F/49ºC, but only at a smal rate, say,1 gallon/3.8 liters per minute - which is not much.
Point of use water heaters save water and energy. You get water when you need it, instantly.
Point-of-use water heaters can be of tank type or tankless.
Tankless point of use water heaters are rated by their GPM/LPM (Gallons per Minute or Litters per Minute) like other tankless water heaters (see: Water Heater Capacity).
Typical point-of-use water heaters use electricity, which allows them to be located close to… the point-of-use. Most existing models can easily be plugged into a common wall outlet.
Point of Use Water Heaters Manufacturers
Bosch and Ariston are the top manufacturers. Other brands with instant electric point-of-use water heaters: A. O. Smith, Bradford White, Eemax, Eltron, Insinkerator, Ruud, Rheem, State Industries, Stibel…
Bosch models are manufactured by the Italian MTS, the company behind the Ariston units.
Both Ariston and Bosch point-of-use water heaters are designed to fit under a sink and to be plugged into an electrical outlet or, in some cases, wired to a circuit box. Most models are tankless, but some Ariston models use a tiny tank.
The best rated models are the 2.5-gallon Bosch-Ariston GL2.5, the 4-gallon Bosch-Ariston GL4 and the 7-gallon Bosch-Ariston GL6 Plus. Their price range is $150 to $200. For reviews, take a look at Amazon.com: Electric Point of Use Ratings and Customer Reviews.
Bosh has units designed to serve two sinks, but they are significantly more expensive and more difficult to install. They have mixed reviews in Amazon.com.