Some smart meters aren’t so smart about Daylight Saving Time


It seems — and is — a geeky thing to write about, but Daylight Saving Time can cause serious problems for some smart meters and meter data management systems.

I know this from 30 years of experience…

Problem 1: Hourly data recorded by smart meters. Conventional electromechanical meters don’t do this; they’re more like an odometer that merely advances continuously. But smart meter systems record usage every hour and mark it with the time the energy was used.

Older time-of-use (TOU) meters — an early “smart-ish” meter technology — do record hourly data. However, they aren’t easy to reprogram. Millions of TOU meters are currently in use.

Therefore, smart meters must deal with that pesky extra hour each autumn. When clocks are set back, there are 25 hours on the first day of standard time. Also, each spring there’s a “hole” when clocks are moved ahead one hour.

Problem 2: Governments have a nasty habit of not cooperating. As the map above shows, nations — and even states or provinces within a nation — have different DST policies.

Many utilities have service territories that cross “DST borders.” Their systems must account for meters in the DST area that gained or lost an hour — or is it for the ones that didn’t? And this happens twice a year.

Problem 3: DST is a moving target. DST rules are subject to change. For example, the U.S. Energy Policy Act of 2005 changed the dates of the time changes: it pushed the fall switch one week back, and the spring change one week forward.

Many countries followed the U.S. lead on this, but Europe has not. So for one week each fall (starting yesterday) and one week each spring, the normal time differential between Europe and much of the rest of the world is one hour different from the rest of the year.

Keep this in mind if you’re calling someone in Europe this week.

So what? These problems often cause TOU and smart meters to report incorrect data. Sometimes data is assigned to the incorrect hour. Other times, all of the data gets time-shifted in the wrong direction — or not time-shifted when it should be. Such problems tends to be worst where the time assignment gets made in custom software, or where reprogramming is more difficult — such as in millions of existing meters in the field.

The result: Billing inaccuracies that can affect large numbers of customers and that require thousands of person-hours of labor to correct.

For example, for some utilities the cost of going out and reprogramming older TOU meters is too high. So every year they simply tell customers that their TOU meters will be off for those two weeks — until the TOU meters are replaced with true smart meters that can properly handle the new DST rules and which can be reprogrammed.

I’ll be reminded by this by my desk phone, which is still programmed with pre-2005 DST dates. Fortunately the clock in my car seems to have switched over properly. Also, my smart thermostat — now run by EnergyHub — is displaying the correct time.

What’s a utility to do? Check your smart meter and meter data management systems, as well as consumer energy data web presentment, for possible DST-related discrepancies. If you find any, correct these problems if you can. But if you can’t fix them, be sure to tell your customers what to expect — promptly and clearly.

I’ll check my own smart meter and online energy data for DST discrepancies when I get home tonight.

This article originally appeared on eMeter’s Smart Grid Watch blog. Chis King is the Chief Regulatory Officer for eMeter. He is a nationally recognized authority on energy regulation and competitive energy markets, and is widely recruited by regulators and legislators to consult on technology issues in electric restructuring and grid management.


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