Sunday, January 6, 2013

Electricity Usage History, My Home

I will look mainly to consumption of natural gas in tracking consequences of weatherization efforts in my home. Yet, I will find lessons for this study in what is offered by my electricity utility. 

My electricity serves a hot water heater, lights, computers, and, until five years ago, a clothes dryer. No electric space heaters. I expect seasonal  variation in operating the air mover of my furnace. I don't know what I might find in being attentive to billing details, and expect charts will not inspire changes of behavior. Here is the best information I may see online at the web site of my electric utility, Pacific Power. It is a bar chart of KWH differences between meter readings, going back two years. Is that what I want?

This chart is sufficient to see that electricity usage is proportional to the number of adult inhabitants, where I had a boarder for three years, ending mid-Winter, 2012. I have all of my bills going back to 1998, and ending November, 2012 when I switched to paperless billing. I can continue to see all details of billing, into the future, with online posts of billing. I wonder what more I can learn from the numbers.  With a significant investment of time, I typed numbers into a FileMaker database. That gives me entry ease, and calculation functions I might not understand in Excel. I readily save the data into an Excel file for a variety of plotting interests. 

A first plot lets me see back to first consequences of sharing my home. A hardly-believable spike in 2009 might include consequences of using CRT computer monitors and a television set. Questioning the spike, I had my meter tested. It's a good digital meter, installed In January 2006, and works just fine. Maybe the boarder did stay toasty with a space heater.

I think I demonstrate to my utility, that line charts are better than bar charts, and that sometimes-large variation in the number of days between readings should be accounted for. A plot of average KWH per day for reading periods is cleaner, and is no more difficult to generate. Charts going back as many years as possible will do a lot more to influence behavior, seeing through seasonal variation.

Online charts must not leave out dollar amounts. Dollars are easier to understand, where some motivational lesson is offered. Dollar amounts will retain the "noise" of variable days between readings.

I go further to test whether rates are applied as we might expect. Here is the variability in rates applied in my billing:

Is anything wrong here? In the Pacific Northwest, most of our electricity is now from coal-fired power plants, not from our hydroelectric dams. I suppose it is fair that we are losing our "cheap" rates. Subsidized cheap power is not good for motivation to conserve energy, so, good riddance. Save our salmon.

Accepting comment, I admit surprise my electricity cost is moving up to national norms, and not due to coal-fired generation. My marginal rate remains under $0.10 per kwh, but as I use less, the $9 per month basic charge rules. That saps inspiration  to conserve. If more people see this, we might act to lower or eliminate the basic charge, boosting the delivery charges. 

Here is an update of my information through October, 2014. I continue to benefit from 2008 conversion to a gas clothes dryer. Really-dramatic improvement since 2011 is from conversion to LED disk lighting, a 90% reduction of employed electricity.

Where billing periods range from 26 days to 39 days, a chart including dollar amounts has more scatter. Through the scatter, see $15 per month savings from conversion to LED lighting.

My utility offers only a bar chart option, of KWH usage for each billing period. It means nothing to me.

1 comment:

C Jones said...

If you want to show dollars, you could show dollars per day in order to remove the meter reading period variability.

With respect to your final comment, some utilities in the PNW are still running on very low percentages of coal, and the only two big coal plants in Oregon and Washington are scheduled to shut down in the next ten years. Rates are increasing for various reasons, but they are still much lower than most other places in the U.S.

One more note: I have a similar graph, and I am planning to play with it a bit to add two features: combined energy use (BTU) for gas and electric, and trend lines that show usage during the same month in multiple years (e.g. a line linking January 2005, January 2006, etc. through January 2013). I haven't figured out the best way to draw those lines, but I think it will be more useful than the up-and-down seasonal graph.