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Best Practices

Calculating the Costs of Electricity Consumption

How to turn electricity usage data into dollar figures to help identify potential savings

These plug-in monitors each cost about $30. The information they yield can point you in the direction of energy savings.

Part of my job as an energy auditor is educating homeowners around electricity usage. Reviewing and analyzing past usage is part of my process. Checking service conductors and individual branch circuits in an electrical service panel is also sometimes needed. This information tells me if an appliance, motor, or other device is operating as expected.

Electricity usage of a single appliance over time is something to determine too. My energy assessement visits are usually under four hours—hardly enough time to figure out how often a unit operates. For this, we need tools that can record data.

Some questions I ask of customers include: Are there any new appliances? Is there electric space heating equipment in use? Are you using a vehicle block heater? Are there tank heaters for farm animals?

Then I test inside the electrical panel.

Electrical panel testing

When diagnosing a high electricity bill complaint, I have a few different methods at my disposal; testing inside the electrical panel is typically where I begin. First, I view the panel with my thermal imaging camera. If a circuit breaker is, or was recently on, often the breaker will be warmer than the surrounding circuits. This gives me a starting point of where to look.

Thermal imaging of electrical panel

Note that thermal imaging is effective when the electrical draw is constant. Sometimes loads are intermittent; those don’t always present using thermal imaging, so you have to be lucky to catch the problem another way.

The next step is to use my clamp-on multi-meter to confirm electrical usage. I start by measuring the load on the two main service conductors. This will indicate the entire draw of the panel.

After measuring the load on the main service conductors, I measure the individual branch circuits, trying to determine if any are drawing an unexpected…

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One Comment

  1. BirchwoodBill | | #1

    The Sense Energy Monitor is okay - but still very useful. As Randy pointed out - it is still learning some new devices (like dessicant dehumidifier installed in the attic). ECM motors are not easily detected.

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