When to Shut Off Your Water Heater

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Is shutting off my hot water tank for a substantial portion of the day a good way to save energy? I’m considering turning it off at night, and also during the day when I’m not home. Is this a good idea? 

Turning off an electric (not gas) water heater for some portion of the day has promise in terms of saving energy. However, this particular timing scenario is a nightmare for an electric utility in terms of supply and demand. Here’s why: Most people tend to leave for work around the same time in the morning and arrive back home around the same time in the evening. Electric utilities experience a significant jump in demand in the mornings, normally from around 6 to 8 a.m., and then an even larger spike in demand when people start to arrive home and take showers, make dinner, turn on the air conditioner, etc. Late-afternoon demand peaks can start as early as 3 p.m. and continue until 8 or 9 p.m., depending on weather conditions and other factors. Why does this matter? One reason is that if too many people are drawing electricity at the same time, utilities can’t keep up, and this results in brownouts, blackouts or rolling blackouts.

On a side note, I’m convinced electric utilities secretly dread the wider use of plug-in hybrids and all-electric vehicles because they expect most folks to plug them in when they get home, drastically spiking energy demand. I predict there will soon be a major campaign to have all plug-in hybrids and electric cars charged during the night hours and not at dusk or dawn. 

In short, while the idea of turning off an electric water heater is a tempting one, I recommend adjusting the timing of the charge cycles. Buy and install a 220/240-volt timer, which should be easy to find online. I suggest turning the water heater on anytime after 10 p.m. Then have the timer shut off the unit before 6 a.m., and turn it on again from 10 a.m. to 3 p.m. This setup leaves the water heater off for about 11 hours a day, which should be a significant energy savings. 

— Kenneth C. Riead, certified energy manager, Hathmore Technologies

For more advice on saving energy with this method, go to www.EnergySavers.gov, and search for “water heater timer.”