Thursday, March 12, 2020

my typical electrical day winter 2

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Daylight savings time changed this past weekend.

I normally check my hourly electricity usage at my utility's website to make sure I've reset the water heater timer correctly so that my hot water heater does not come on during peak priced periods. The water heater is a big electricity user here that I can see easily on this chart. Since I have kept it off for twelve hours, it takes a big gulp when it comes back on, when it's cheaper after 7pm. Cheaper by half!

[click any pic to enlarge]

As a single person, I don't use a lot of hot water yet I NEVER run out of scalding hot water during the daytime. Even at 6:45pm after twelve hours OFF (graph of actual water temperature below).

Your mileage may vary. I have a relatively new heater which is a huge improvement over the old one. I am only one, relatively frugal person as a hot water user.

On the Hydro One website (pic above) I can see my water heater coming back ON (biggest bar in the green) yesterday, five minutes after the end of On-Peak pricing. I use a cheap but great timer that does the job perfectly. It is somewhat cryptic to set if you only look at it four times a year. The light is not very good and I need to remember a flashlight.

I did it wrong once and made the situation worse with the heater off for six hours (doing the right thing) and then coming back on in the last hour of peak price, costing me twice as much!

Because my water heater is a wired in appliance running 240 volts, I can't use the sort of web enabled timer/monitor that I was using for smaller plug-in appliances, like the Itead Sonoff S31.

Compare with the daytime winter electrical picture of three plus years ago. At the time, I was using my own smart meter reader which had higher resolution so it looks more jagged. The big spikes (marked W) from the water heater were easily seen. I was trying only a few hours of On-Peak inhibit at the time (marked C). I was also inhibiting the refrigerator and the freezer so the house energy draw drops almost to zero during C.

I'd like to get a web enabled wired-in device for the water heater but I'd still have to check four times a year that it is set correctly. My utility rate changes happen twice a year on a different schedule than the daylight time changes. Four changes per year to check.

Water heater inhibit is a big winner for me as far as savings on my electrical bill. I estimate that the new water heater and the inhibit technique save me between 15-20% on my electricity bill. This is possible because I use less electricity and only off-peak for hot water.

Off peak timing is quite different from lowering the thermostat temperature of the water heater which is actually quite dangerous.

I have the tank thermostat set at the recommended 49C so that Legionnaires’ bacteria are minimized. The tank cools about three degrees after twelve hours off. Returns quickly to the set point at 7pm until the next morning.

Sorry if the graph is difficult to read. It is from the top of my water heater tank today and shows the low temp for the day and the rise to set point.

I'd mentioned my ambition to leave the grid entirely during On-Peak in future.

Thank you for your interest.

George Plhak
Lions Head Ontario Canada

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