When doing a Home Energy Audit, I always tell people that what I find is not good or bad. I tell them that what I can recommend for improvement depends on the cost of their Utility Bills.
If you have a water leak, we all know that paying the price to a plumber to fix it, will cost us when the plumber comes. We also know if we don’t fix it, we can pay the water company that amount over 1 or 2 or 6 months. How long depends on the amount of the leak and the cost from the Utility for your water. And then we still have to pay the plumber. so we make a choice.
Some choices are easy, for improving the efficiency of a home. Most homes with a tank type hot water heater inside the home, in a balanced or cooling climate (south of the Kansas / Oklahoma border) will benefit from installing a water heater insulating blanket. They cost about $25.00 and typical savings just north of the above line can run from 6 – 8 dollars per year. So at $6 bucks a year, the blanket pays for itself in about 4 years. And most people can afford $25.00.
Other choices are somewhat tougher. Instead of $25.00 to invest in the improvement, cost can run $2,000 to insulate a basement. If you spend time down there, you know it is a little colder in both the winter (brrr) and the summer (nice), then upstairs. Again, using some Wichita area numbers a homeowner could save in the area of $350 per year. Each house is different, so I am using some averages from various audits. If you apply this savings over 6 years, the insulation is paid for and you still save the money. The hitch? It is harder to come up with $2,000 instead of $25.00.
In 2011, I had an Energy Efficiency Project approved under the Efficiency Kansas Program. They loaned some cost, I paid some costs and we added some (a bunch) of insulation, air sealing to cut the infiltration, replaced a 18 year old furnace and air conditioner. I also added an Energy Recovery Ventilator.
My payment over the 15 year loan is 870 per year, due monthly on my Utility Bill. So the question is, how did I do with saving some money? I have been tracking my Natural Gas and Electric billings, with numbers going back to 2009. When I changed HVAC systems, I went to an electric Heat Pump with a gas furnace for back up or emergency heat. As a result, my gas bill dropped and the electric bill, which includes the loan repayment amount is higher than I can remember.
To account for the change, I had to do something with the natural gas, billed in MCF (1,000 cubic feet) and the electricity, billed in KWH (kilowatt-hours). I decided to convert the gas usage to KWH for ease in comparing before and after. I also wanted to be able to compare usage against the weather. Some summers are hotter than others and some winters are warmer then others.
The National Weather Service tracks our weather very well. You can get an F-6 Report from most airports around the country. In Wichita, we have a choice of 3. There is Mid-Continent, the primary commercial airport; there is Jabara Airport, a smaller facility that specializes in private airplanes. And we have McConnell AFB. All have weather observations and reporting.
How did I compare the before and after? Excel works great for prototyping number crunching and charting the results. I collected my data on usage, cost and Degree Days from the Weather Service. I built two charts. First one covering January 2009 through present. After looking at this chart, I built another showing January 2011 through present.
The charts show three (3) lines. The Blue Line represents Heating Intensity by month. I took Heating Degree days, multiplying by 5. The Red Line represents Cooling Intensity by month. I took Cooling Degree days, multiplying by 3.5. The Green line represents Energy, show in KWH. I converted my gas usage to KWH by ” MCF x 293 “. Then I added the KWH from Electric and Gas to chart the Green Line.
2009 2010 2011 2012 2013
If you look at the top peaks of the Blue Line – you see the cold months. Imagine a level line averaging those tops. Somewhere between 4000 and 5000 on the Y-Axis. Look at the Red Line Peaks – you see the hot months. Imagine a level line on the Average of those peaks, just a little over the 2000 on the Y-Axis.
Now look at the Green Line, it goes up in the winter, and summer, down in the spring and the fall. This line doesn’t really run level on the peaks. If you pick about 6500 on the Y Axis in 2009 and 2500 in 2013, the line slopes down. The Red vertical line shows when the improvements were made. This chart shows 3 years prior to the date of improvements and 1 year after.
The Chart below just shows one year before and 1 year after. So the horizontal spreads out a little. I think the point is made in either chart. The improvements require less energy to be purchased.
How much less in dollars, instead of Energy Usage? I’m saving my 870 annual repayment amount plus enough to repay myself over 15 years for what I kicked in. And a little extra.
2011 2012 2013
Some one will ask why did I adjust the HDD and CDD numbers. I did it to match the scales on the charts. I first set it up with direct numbers. When you looked at the chart you could not make out any significant ups or downs to compare. So I reworked the numbers with multipliers, to make the charted numbers line up better.
In September, 2011 the chart shows 155 HDD, 591 CDD, the energy usage in KWH is 2261. In September, 2012 the chart shows 0 HDD, 960 CDD with 1217 KWH used. Using the same Y-axis scale required some changes. So I used a multiplier to move from direct Degree Days for Heating and Cooling to an intensity measure for heating and cooling.
Thanks for following along. I will make another post with more of this story.