If your home is heated by a boiler — any boiler (hot water or steam, oil or gas, mid- or high-efficiency) — you have every reason to heat your domestic hot water with an indirect water heater. Some of the benefits include:
- High efficiency — When you use your boiler as a heat source to produce your hot water, the water is heated at the same efficiency as your boiler. Some high-efficiency boilers reach 96%. The average gas water heater is about 60 - 70% efficient.
- Reduced heat loss — An indirect water heater is very well insulated and loses very little heat during long stand-by periods (at night or while you’re away). A gas water heater is always losing energy up the chimney.
- High performance — The performance of an indirect water heater is a direct result of the boiler it’s connected to. Given the size of most residential boilers, it’s not unusual for an indirect water heater to produce two to three times the amount of hot water as a standard gas water heater.
- Longer life — Most indirect water heaters have a lifetime tank warranty. It will likely be the last water heater you’ll ever need. The manufacturers can offer this warranty because their tanks are not subject to the abuses that a direct-fired gas water heater is. And many of them are made from stainless steel to prevent corrosion.
- Hot water storage. Available in sizes ranging from 30 - 200 gallons or more, hot water can be stored for high-volume flow-rate usage when you need it.
“But Wayne,” you may ask, “doesn’t this mean I need to run my boiler all summer now, too? Won’t that cost me a bundle?” Au contraire, my energy-conscious friend. The only time the boiler fires is when you need hot water. And when it does fire, it’s producing hot water at a higher efficiency rate than a typical water heater. Other than that, it sits quietly and waits. The belief that the boiler is running all summer may be a throw-back to the days of tankless coils in older boilers. They had no storage capacity, so the boiler needed to stay hot all the time to produce hot water on demand.
“This is all well and good,” says the the intrepid Internet traveler, “but I’ve been hearing that the new tankless heaters are the greatest thing since Apple went public. Can’t I save a lot more money with one of those?”
Well, speaking of apples, this is really an apples vs. oranges comparison. A tankless heater usually has little or no storage capacity, meaning it needs to heat the water instantaneously. And it can do that — with some limitations. Older tankless heaters drop the temperature at high flow rates (two fixtures running). Newer models limit the flow rate to maintain the delivery temperature. An indirect heater can handle that high flow rate without reducing the temperature or flow. And, depending on the size of your boiler, it can do it while delivering almost limitless hot water.
Better tankless heaters have efficiency ratings in the 80 - 95% range but typically last just 15 - 20 years. An indirect water heater connected to a 15-year-old cast-iron boiler will deliver hot water at 80 - 82% efficiency. And one connected to a modern modulating/condensing boiler can deliver 96% efficiency. So while tankless water heaters are efficient, they can't beat indirect water heaters.
Indirect water heaters can also reduce your maintenance costs. Having only one gas- or oil-fired appliance means less service. A tankless heater needs to be serviced every year. If not, you can count on reduced hot water production, possible heat exchanger failure and loss of warranty coverage. An indirect water heater requires little additional maintenance beyond your annual boiler safety and performance check-up.
The next time you’re in the basement, take a look at your existing standard water heater. If it's a little worse for wear, you may want to remember that the typical water heater life is 12 years. Wouldn't it be nice to replace it — once and for all?