When people think about saving energy through efficient water heating systems, they typically focus on condensing tankless gas water heaters or heat pump water heaters. Some consumers may consider efficient showerheads, low-flow aerators, or the location of the water heater itself; noting that installations inside the home—instead of the garage—will likely lead to savings.

Each of these inclinations is correct, but there is more to consider. The rule for maximizing savings through efficient water heating is: Yes, the traditional measures are important, but it’s also critically important to think through distribution losses to get the most savings from water heating systems.

The key distribution considerations stem from the volume of water in the pipes between the fixtures and the source of hot water. A pipe’s length and diameter determine how much water it holds between uses. If there’s a gallon of water in the pipes between the water heater and the faucet, then that gallon of water will need to be cleared before hot water reaches the fixture. However, if the water in the pipes is still hot, there will be a shorter wait to get usable hot water.

It comes down to keeping hot things hot. Insulating hot water lines can reduce heat loss so hot water cools more slowly. Similarly, it is best not to waste water while waiting for hot water to arrive at the faucet. Unnecessary waste can be prevented by using efficient plumbing layouts or on-demand recirculation systems. These methods reduce time spent waiting for hot water to arrive from the water heater, and also decrease the amount of cold water that goes down the drain.

^{Core plumbing layout image courtesy of Building America Solution Center}

^{Demand plumbing layout with recirculation image courtesy of Building America Solution Center}

To learn more, check out Part 1 and Part 2 of Gary Klein’s presentation on behalf of the US Department of Energy.

To learn more about maximizing efficiency in hot water distribution systems, contact the EPS New Construction team at 1.877.283.0698.