Unless you have been living under a rock, you can’t help but notice that lately everyone seems to be eager to conserve or reduce their energy consumption and increase the efficiency of the items they purchase. Not only is it the popular thing to do, most consumers expect substantial savings by spending less on the energy needed to power our lives. I suspect, however, that very few people actually measure how much energy they are saving.
In fact, there is an effect called the Jevons Paradox that states that as consumers save energy, this naturally results in the cost of energy becoming cheaper. This then causes economic growth and consumers use even more energy than before! Still, the argument exists that you cannot understand or begin to control your energy consumption until you actually examine the data. Knowing your usage will lead to, hopefully, more responsible choices going forward.
To begin to understand my energy consumption, I started by collecting my historical energy usage from old electric bills. I even contacted the local electric company to ask for copies of missing bills so I could fill out my data.
I also did the same thing for my natural gas usage. Everything I collected went into an Excel document for further analysis.
This allowed me to generate some graphs showing the electricity and natural gas usage as a function of the average monthly temperature.
I used the average monthly temperature as the X-axis since a monthly plot does not take into account one month which happens to be an above or below average temperature for that year.
When the furnace needed to be replaced, I added a heat pump to the setup. The heat pump was sold to me on the basis that the cost per million BTUs was about one-third as much as a natural gas furnace. Sounds like energy efficiency, right? Now that it has been running for a while, how do I prove that I’m saving money? I know that a heat pump uses more electricity, so that cost should have gone up.
The month with the heat pump is the first one above. The second image shows a typical month with gas heat from two years prior. Notice the two numbers above were taken from two different months with the same average temperature. This is important to see if my usage at a given temperature has gone up or down.
I also know that using a heat pump means I’m not burning as much (or any) natural gas, so that cost should have gone down.
The first image above is the natural gas used with heat provided by the heat pump. The second image above is a typical month with gas heat about two years prior. If I combine the two numbers and compare it to historical data, I should be paying less. When I compared the total invoice cost of operating a heat pump for heat versus a natural gas furnace for heat, I found that I was saving $14.15 last month ((New electric bill + New natural gas bill) – (Old electric bill + Old natural gas bill)). So the installation of a heat pump has actually started to pay off! Granted, this is only one month of data and a little lower than I expected, but I fully expect this savings trend to continue. At least now I know how to measure it. Knowledge is power!