KWh-meter installed

KWh-meter display after a quick charging test, showing 0.3 KWh used.

No more guess work on how much electricity we’re using with the Leaf. Today we had a KWh-meter installed that is going to show how many KWh are being consumed by our Charging Station.

So far I’ve been doing all the measurements using a combination of manual logging of charging hours and reports from the smart meter in our house. None of the two are very precise. They only give us a rough idea of much is being consumed. With the KWh-meter we will be able to tell precisely how much we’re spending each month in electricity. The meter doesn’t measure how many dollars are being spent, just how much energy is being consumed. We still need to multiply the measurement by how much we’re paying for the KWh, but the price varies depending on when we charge. This is because we have time-of-use rates, with different prices for different times of the day. We charge almost exclusively during off peak hours, at a rate of 12.8 cents per KWh, all included, but I’ll still need to keep track of any eventual mid-peak or on-peak charging to get a more precise dollar amount at the end of the month. Luckily, these have only happened during the winter so far.

The KWh meter is manufactured by a company in California called EKM Metering. The unit I purchased is one recently UL-certified for use in Canada (electricians will normally refuse to install any non-UL certified equipment around here). I had to wait quite a few months for the certification process, but once the unit was available, shipping across the border was quite fast, with no extra fees other than the S&H. The only caveat is that you have to order the enclosure and the required CTs (current transformers) separately.

The meter also has a serial interface for remote reading by a computer. You’ll need a special RS-485 to USB converter, which EKM sells for $20. I haven’t hooked it up yet but I will in the future. They also have software available and it’s free.

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