Solar water heaters add to home’s energy efficiency

By Ann Robinson and Annie Vernon
Published: Sunday, April 25, 2010 6:15 p.m. MDT  

Recently, we wrote about tankless water heaters.  

Following its publication, we were contacted by a nice gentleman named Larry Wilkins.  

Wilkins has been in the tankless water heater business for many years, and operates a company called Envirotherm.  

We visited his office so he could share his expertise and enthusiasm for tankless water heaters. Wilkins emphasized that tankless water heaters can increase the energy efficiency of your home in more ways than one.  

 

As you may recall, a tankless water heater is a small, electric- or gas-fired appliance that takes the place of a standard water heater.  

The traditional unit that probably stands in your basement has a 30-gallon to 75-gallon tank of water that is kept heated day and night, whether you need it or not.  

A tankless unit runs water on demand through a small maze of piping where it absorbs heat from the burner assembly and then passes out into the supply system.  

The tankless water heater saves money, since you are not burning energy to maintain that large tank of hot water 24/7 in your home.  

But with its initial cost being two to three times higher than the standard water heater, there is a monetary payback factor to consider. On the plus side, because of the greater efficiency, there is also an environmental savings of thousands of pounds of carbon dioxide each year.  

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Although a tankless water heater is pretty impressive on its own, Wilkins pointed out that it is also possible to convert your forced-air gas furnace to use hot water to heat the air it blows by removing the burner units and installing a fan coil.  

In a typical forced-air unit, when the thermostat tells the system that room temperatures are below a set comfort level, the air handler kicks on, drawing room air from a “cold-air return” through ductwork into the furnace’s heat exchanger, which is a combustion chamber around which the air flows.  

This heat-exchange system can be removed and a fan coil installed in its place within the furnace body.  

It is this coil that uses hot water from the tankless unit to transfer heat to the air moving through the furnace and out into the ductwork system in your home.  

Wilkins says if you are interested in further improving the energy efficiency of your home with your tankless water heater, you can install a solar water-heating system. These systems are generally composed of solar thermal collectors (two panels on your roof or wall) and a water storage tank that stores the solar-heated water for use in your home.  

There is a mixing valve to regulate the temperature of the water coming out the tank if the stored water is too hot for domestic use, and there is also a connection to the tankless water heater that will kick in if the water in the tank falls below a certain temperature.  

The water from the tank will then be pulled through the tankless heater to boost its temperature to the desired level before it is distributed in the house.  

Of course, the system is not quite as simple as this, but hopefully you get the general picture. Wilkins estimates that the entire system will cost approximately $16,000, including rebates that are currently available for this type of upgrade to your home.  

The payback on this is somewhere in the neighborhood of 10-15 years, but in addition to benefitting from your increased independence from the power or gas company, you will also be eliminating significant amounts of pollutants, such as carbon dioxide, sulfur dioxide and nitrogen oxides from the atmosphere.  

Currently, this type of system makes more economic sense than a photovotaic system (where you are actually generating power from solar energy) whose payback is about 2 1/2 times longer than that of a solar hot-water system.  

While existing furnaces can be adapted, the best time for you to consider this approach is when you need to replace a furnace. And if you need a new water heater at the same time, here’s your big chance to further investigate this opportunity to bring your home into the 21st century.   

Architects Ann Robinson and Annie V. Schwemmer are the founding principals of Renovation Design Group, www.renovationdesigngroup.com, a local design firm specializing in home remodels.  

 Reader comments:

The savings can be even greater. I had solar thermal panels installed along with a tankless unit as a backup on sunless days. My yearly average savings over my old traditional heater has been 85%. Actually during four to five months a year we use so very little gas that we have to pay the city their minimum charge $15. With that we get endless hot water for everything. At the current pace of savings the whole unit will pay for itself in about 7 to 9 years.