From late January to early February, Crista and I did not touch our thermostat. It stayed at 68 degrees, 24 hours a day. After taking three meter readings over that time period, PRISM estimated our annual usage to be 1,376 (+/- 73) therms. Just as a refresher, with the house under the exact same conditions using a six degree setback, the house's annual consumption was 494 therms.
So by being lazy, or comfortable, or whatever one's reasons for not setting their thermostat back, the additional running of the furnace added over 800 therms of energy usage. However, more important is the inverse. By setting the thermostat back six degrees during work and while sleeping, we were able to save over 800 therms and lower our consumption by 64%.
As is evident from the PRISM plots, only three data points were used to estimate the annual savings without using a setback. Which means while the normalized annual consumption estimate is reliable, it would be poor form to put too much emphasis on that estimate.
To further explore the thermostat's effect on our house's energy consumption we're now using a three degree setback. Six degrees may be a bit extreme for many people. Three degrees might better represent a more acceptable level of setback for most people. It is also more affordable for us to run our house at for longer periods of time. That way more data points can be collected and PRISM will have more data to model.
