Is a hot water heater blanket always more efficient?

Putting a blanket on your hot water heater saves heat that you would otherwise lose to the air, a process known as jacket loss. But in some cases, allowing your hot water heater to shed heat could be more efficient than space heating. It depends on the type of hot water system and heating systems you have, how efficient they are, how much water you use, and many other factors.

Our building science research team is studying the interaction of these systems to determine when a hot water blanket is helping, or hurting, your overall home efficiency.

“Our theory is that it depends on the circumstances, and you can’t make an absolute general statement of one over the other on any of these questions,” says CCHRC building energy economist Nathan Wiltse.

We will simulate a highly efficient home, where any difference in energy use could likely be attributed to appliances. We will use energy models to test various configurations—water tanks versus on-demand heaters, high versus low water usage, boilers versus furnaces, the temperature settings of these systems, etc.

For instance, what if you have a radiant floor system set at 110 degrees, and a hot water heater set at 140 degrees? You may assume you’re better off using a hot water heater blanket, because it requires more energy to maintain the hot water tank at 140 than the floor loop at 110.

But if you have a 65-percent efficiency boiler and a highly efficient water heat, it may actually be better to allow those jacket losses. We won’t know til we run the simulations.

We’re going to create a matrix of the scenario results to show a number of the factors at work. We plan to share it sometime in January, so you can compare your own home heating information and see what might be the most efficient for your house.