Water heaters from Marathon, Rinnai, Bosch & Eternal

For most of us, there is nothing like a hot shower or bath to start the day or end the day in a better mood. In general, we all spend about 30% of our home energy bill making hot water. In New England a large majority of us use oil to heat our homes and make the hot water. In the winter when the oil burner is heating the house, using the oil burner to also heat hot water is a fairly efficient endeavor. But when you are not heating the house, that pesky oil burner wastes a great deal of fuel just making hot water. On top of that, many of us have what is called a side arm tank, which is storage for the hot water we make. Now, since oil has always been relatively cheap, most of these tanks were not designed to store that heat as long as possible. The tradeoff between better insulation and more fuel usage always fell on the side of relatively inexpensive fuel.

hot shower 

This is not just true of side arm tanks. Your average three to four hundred dollar electric water heater is no energy miser either. Gas fired tank heaters are pretty much the same and, in addition to the lack of insulation, a fair amount of heat goes up the chimney pipe.

Today there are several options for cutting our hot water bills. The most obvious is cutting consumption. Low flow shower heads and shorter showers can save an amazing amount of hot water. Insulating tank water heaters can help as well. Beyond the simple stuff there are several options for producing and storing hot water more efficiently when solar hot water is not an option.

The Marathon electric water heater is unique in the water heater world. It is an all plastic tank with four inches of foam insulation. It is rated to lose no more than 1/2 degree per day which is a pretty amazing feat. Our partner, Jay Lawrie, has a weekend house in Maine. To save energy he turns off the Marathon water heater when he leaves for the week. When he returns on Friday night the tank is still hot enough for a shower. That is simply amazing. Half the trick to saving energy is to store as much of it as possible. Heat that is lost because of poor insulation is just that, lost.

Rinnai instantaneous gas fired water heaters are a different animal. If you assume that storing large quantities of water is bad, then making it when you want it is good. The Rinnai and many other brands like it have a set of large burners in them to heat hot water only when you call for it. In addition to that, you have more control over how much you make. If you step into the shower and turn on the hot water, and then turn on the cold water, the hot water is too hot. With a tank water heater you usually want water hotter then your needs so you won’t run out. With a Rinnai you can never run out, and with their handy wired or wireless remote you can just set the exact temperature you want when you want it. The other great thing about a Rinnai is that its burner modulates. This means the amount of gas consumed is dependent upon the incoming water temperature. If your water is 50 degrees coming out of the ground, the Rinnai will fire on all cylinders, but if you have solar heated water at 80 degrees the Rinnai will use fewer burners, and therefore less fuel. Two additional benefits of the Rinnai, it has no pilot light so no wasted gas and it uses outside air for combustion. As you tighten up your house this becomes more important.

Bosch is another company that makes instantaneous water heaters. They make a model that is perfect for the off gridders among us. While the Rinnai requires a little bit of electricity to operate, the Bosch actually has a peizo electric triggering mechanism that will fire the water heater when you turn on the water and has no pilot light. So there is absolutely no electricity required to make hot water with the Bosch.

Finally, there is the Eternal. The Eternal is best described as a hybrid. Many houses and commercial installations as well have hot water demands a great distance from the hot water heater. The solution to this problem is usually a ‘recirc’ line, meaning water is constantly circulated from the storage tank to the destination and back so the pipes are always hot. This requires storage but if you want an instantaneous water heater you don’t have storage. The Eternal is called a Hybrid because it is an instantaneous gas fired water heater with a 4 gallon storage tank. Keeping 4 gallons hot in a well insulated tank is much less work then 80 or 100 gallons. And it is just enough to keep the hot water pipes hot. So the Eternal is the best of both worlds. It can use outside air for combustion and it modulates so it will work extremely well with solar hot water.

seacoast energy marathon with cutaway

Marathon Electric Water Heater

Rinnai instantaneous water heater