Jason's notes

Measurement Project

For my measurement project, I want to track the energy usage of my water heater. And see how much energy can I save if I switch it off when I don’t need it. I’m also curious about if the weather (temperature) could affect the energy cost since the initial water temperature may be higher when it’s a hot day.

It’s been several weeks since I installed the smart plug, and here is the data.

  • Feb 23th to Mar 1st: The heater is always-on as usual.
  • After Mar 2nd: I only turn on the heater before I need hot water.

chart showing the electricity usage of the water heater

The huge difference between Mar 11th and Mar 12th may because that I took a shower after midnight and another one in the evening.

Although there are so many factors that can affect the result, it is still pretty obvious that my action reduced energy usage. The calculation shows that I save around half of the energy if I turn on the heater before I use it. After some research, here are the reasons I believe that is causing the impact.

  • I won’t turn on the heater for casual work like washing dishes. The remaining temperature is enough for these kinds of tasks.
  • Water heaters need energy to maintain higher temperature. Since I’m having a pretty small water tank, I need to set the temperature at maximum so it can offer a 10-min shower. Hence, it wastes a lot of energy even idling.
  • The pipes are not heat-isolated, so they always leak heat. When the water temperature is lower, they leak less.

water tank with metal pipes

It is very interesting to see that result. I think I’ll maintain that habit.