Calculating Baseline Energy Use   1 comment

The easiest task in a personal home energy audit is to analyze electric and gas bills to observe patterns. If there’s a time of year, like spring or fall, when for an entire billing cycle neither cooling nor heating is needed than it’s pretty easy to determine an average typical non-HVAC daily and annual energy use. Then it is pretty easy to subtract and  determine how much cooling and heating increase energy demand during the appropriate season. It’s a rough calculation, since there may be seasonal fluctuations to the “typical” energy demand like more lights on during winter, but it’s a good start. I calculate that we typically use 10-11 kWh per day non-HVAC, which comes to 3,840 non-HVAC kWh over the course of a year (65% of total). Heating required approximately 990 kWh for the year (15% of total), and cooling required approximately 1,200 kWh for the year (20% of total).

The next task is to break down that “typical” energy use a bit, but this requires a bit more effort since you have to read the meters. Reading the meters isn’t challenging, especially now that digital smart meters are being rolled out. I hear that some utilities are already using the smart meters to provide customers with real-time tracking ability from their computers, but walking into the back yard and reading the meter really isn’t much work. There are a few different strategies for meter reading schedules. You can read it once per day to get a feel for your real “typical” energy use and the fluctuations, you can read it twice per day to differentiation baseline and active use, or you can read it many times per day to track specific appliances.  The latter is what I did last time I did a home energy audit, and it is a BIG PAIN! So this time I have a Kill-a-Watt to do the measuring for me, and we did twice per day readings. For a couple of weeks I read the meter immediately before going to bed, and Mike read the meter as soon as he got home. During that time there was very little active use of electricity: a toaster or blender for breakfast, a brief light on in the pre-dawn, and the garage door. I consider those to most likely be negligible over the 15 or so hours of baseline energy use. What I mean by baseline is the stuff that is always on: refrigerator, cable box, thermostat, etc. It’s the baseline because even if you eliminate all active energy demand the house will still draw this baseline amount. It’s relatively constant, with minor fluctuations like water heater working harder in winter and fridge in summer. So now I know that our baseline home energy use is approximately 4.8 kWh per day, which is almost half of our typical daily energy usage.

There’s very little that I can do to reduce that baseline energy usage. I’m not getting rid of the fridge or the alarm, and while I would love to turn off the cable box I can’t without breaking it. What I want to know is how much of that baseline goes to the water heater. By using the Kill-a-Watt I’m measuring as many of these baseline contributors as I can and then I’ll be able to calculate an estimate of how much hot water contributes to our energy usage. My guess is that it is most of the baseline.

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Posted September 2, 2011 by mayakey in energy use, home

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One response to “Calculating Baseline Energy Use

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  1. Pingback: Energy Vampires Beware! The Kill-A-Watt Meter Is Here! « Love Knowledge Zeal & Fortitude

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