One of the most cost effective solutions for hot water is an on-demand tankless hot water heater. Most homes in the US have a large water tank that is heated all day, despite the fact most hot water is consumed within a few short time frames. In business applications keeping a water tank hot all weekend when the office is closed is a waste of money. Worst of all is oil boilers that do space heating and hot water but are tankless. This is the most in expensive and inefficient way to make hot water or provide space heating. All solar hot water systems require a backup for days when sufficient solar energy is not available. In Maine this is often a boiler as it is often the most cost effective. On-demand water heaters are also an excellent option.
An on-demand unit can instantaneously provide hot water right as it is need it, without the cost of continuously heating a large storage tank of hot water. They have thermal efficiency ratings as high as 95%, and with no pilot light you save an additional 48 gallons of fuel per year. When the hot water faucet is turned on the flow triggers the burner, which rapidly heats the water as it passes. When the flow stops, the burner turns off. It is important to select fauctes with high enough flow rates so the on-demand unit fires. With a tankless on-demand water heater there are no worries about running out of hot water because there is no tank to become empty.
Tankless water heaters are small and self-contained. Normally they will be installed in the same area your existing tank is located. The units we normally sell are designed to provide hot water for all existing needs throughout your home. We also install small point of use units for specially applications.
Visit the US dept of energy site for a good summary on tankless water heaters.
There are many types of “electronic ignition” and almost all work well and have a long lifespan. While units with pilot lights can be less expensive to buy, your costs over the life of the item are much higher. In fact, by the end of the first year your savings are normally “burned up".
When combining solar with an on-demand unit it is critical to pick one that can process warm incoming water. When the solar system is unable to meet the needs the tankless hot water system will bring the water up to normal domestic temprature, usually about 120 degrees. The water in the tank might be 110. In this case the on-demand water heater needs to raise the temperature only 10 degrees. The unit will modulate firing the multi-stage burner at a low rate, using very little fuel, and providing a small amount of additional heat. Cheaper on-demand units cannot handle warm incoming water because they have only 2 states: on and off. When the warm water gets blasted by the burner running at 100% the water flashes to steam and the safety control shuts down the system.
There are also mini units, commonly referred to as “point of use” heaters. They are designed to provide hot water to 1-2 faucets, such as just one bathroom. These would not normally be used as part of a solar backup system. But they are a cost effective way to supply hot water to a single area. Often these small unit are run on electricy which keeps installation costs low. Larger units are almost always gas.
Compared to an electric water heater, on-demand will save 25% or more (avg. use of 40 gallons per day). They are especially good fits when water use is very small or highly variable. The are excellent for small office buiildings. Replacing your current water heater with an on-demand unit today can save you money immediately as well as become your first step towards installing a solar system.
Call us for more information about determining is a tankless unit is the right choice for your application
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