Blogs > Tom Miller > May 2011

Couple of Things...

Finally, some numbers to crunch.  

It’s now been a year since the insulation, geothermal system and building envelope sealing have been completed on our 50-year-old home in Indianapolis. Enough time to see the effects on energy consumption across all four seasons.

The last of the work was completed in April, 2010, so I used the May, 2010 through April, 2011 time period for a comparison (see complete charts below).

There was no surprise that our natural gas usage went down…but we didn’t quite expect it to drop as low as it did. From an annual usage of 2,193 therms in 2009 we are now using just 287 therms a year. This is less than a single month’s usage during the winter heating season, or an 87% reduction. That’s the good news.

On the electricity consumption side of things, we used 36,500 KWh, compared to a bit over 30,344 in 2009, or about 17% more. The electricity consumption went down, predictably, during the cooling season, and up in the winter.

So, to get an apples-to-apples (or therms-to-therms) comparison, I converted the additional 6,205 KWh to therms (1 therm equals 29.3 KWh), which equates to 211.7 therms.

NET ENERGY SAVINGS: 1,694 therms (2,193 therms minus the 287 actual therms used, minus the 211.7 equivalent therms of incremental electricity) or 49,634 KWh equivalent savings.

In speaking with another geothermal homeowner neighbor, he offered a piece of insight that I hope will make a difference going forward: during the really cold weather this winter he noticed that his back-up heat source would come on quite frequently. He also began experimenting to see if a slight change in the thermostat setting could switch off the back-up fuel…and it did.

So the next project is to have a sensor hooked up to the geothermal system to indicate when it begins using back-up electricity. This way I can experiment to see if I can lower the electricity consumption.

As far as water usage goes, I learned that the water company only actually checks the meter once every four months or so. They use an average for the months they don’t check (4,488 gallons) and then balance it out when they do take a reading. So it’s pretty safe to say, looking at the history, that our water consumption is pretty consistent. This feels like it might be higher than average, so a bit more investigation is in order to see if we can reduce consumption.

Green = 2010/11 annual usage



Posted: 5/19/2011 5:24:51 PM by Heather Wallace | with 2 comments

About Me

Tom Miller is not a building scientist, green guru or even a halfway decent DIYer. However, he is passionate about making a difference, ecologically speaking.

The purpose of Tom’s blog is to share experiences and observations from a homeowner’s perspective in the hopes that it will help building professionals spot unmet needs and dramatically increase the velocity of green building adoption across the country.


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