Tankless hotwater heaters are all the rage right now. Claims of decreased energy usage by ½ are common. These are also called instant hot water heaters, which leads to confusion. While a good product for certain uses, shelling out the dough for tankless hotwater heater will not necessarily green up the planet.
In Western Oregon, there may be no or very little energy savings when tankless are compared to conventional hotwaters, if both are located inside the living space. For either style of hot water heater, the energy used to heat water is shed into the environment. So, the energy used to heat the water in turn heats your house. If you use air conditioning, there will be an added cooling load for the couple of months it’s needed.
While the hot water is made instantly by a tankless model, that does not mean you’ll have hotwater immediately at the tap. In fact, if you locate the tankless model in the same place as your old hotwater tank, it will take exactly the same time for the water to turn hot at the tap, or other point of use.
I went to Jerry’s, the world’s greatest home improvement center, and talked with them. They stock all kinds of hotwater heaters, and they’ll help you size your water heater, which will depend on the number of major draws. Tankless hotwater heaters cost around $1,000 for an average house, compared to about $350 for a tank model. For both hotwater heaters, both electric and gas models are available. The electric models of tankless hotwater heaters require some serious dedicated circuitry: 60 amps for a very small, one draw unit, and 120 amps for a full house model. Older houses may have only 100 amps available at the panel, and newer standards are for panels of 200 amps. For comparison, an electric clothes dryer needs 30 amps, a traditional hotwater heater needs 30 amps, and a stove needs 50 amps.
Instant hotwater at the tap requires a different set up, namely a recirculating system. The price for these are about $300-$400 in materials. This set up actually increases energy consumption, because it keeps water at the tap hot at all times. One other option for instant hotwater is to have a small point-of-use tank located near the tap.
The chief advantages of tankless hotwater heaters, as I see it, are: that they can be located outdoors, thereby conserving living space, and they don’t run out of hotwater, which is useful if you need to fill a large bathtub.
It’s interesting that you point this out. The local real estate agents that I have spoke to during open houses all seem to be in love with the “new system”. On the other hand, I lived in Asia for 18 years and just about every Asian country relies exclusively on these types of water heaters. And I was never impressed with them at all.