A Thermostat That's Smarter by Half

Albert Einstein

Last fall I installed a 'smarter' thermostat as our old bimetal thermostat had started short-cycling the furnace. A local hardware store had a sale on programmable thermostats for $25, and I installed one that day. Within a day or two I had the thermostat programmed to our preferences and I haven't touched it since. The one question remaining - is the new 'smart' thermostat more energy efficient than the old 'dumb' one?

I can happily say that the new programmable thermostat IS more energy efficient!

'Dumb' Thermostat Natural Gas Usage

  • Jan 12 - Feb 9, 2011 (28 days)
  • Natural Gas used = 60.8 Therms @ $58.37
  • Heating Degree Days = 1029
  • Therms per Heating Degree Day = 0.0590

Programmable Thermostat Natural Gas Usage

  • Jan 10 - Feb 8, 2012 (29 days)
  • Natural Gas used = 51 Therms @ $47.03
  • Heating Degree Days = 911
  • Therms per Heating Degree Day = 0.0559
  • 5.1% Reduction in Natural Gas Used

Return on Investment

  • $27.04 = total project materials cost
  • 301.05 Therms = Oct '10 - April '11 natural gas usage
  • 5.1% = 15.35 therms
  • $1.1568/therm = average cost per therm for the past year
  • $17.76 estimated annual savings
  • ~1.5 year estimated payback

While 5% isn't a massive improvement, it definitely adds to the changes we've made in the past 4 years. As I work from home, I haven't set the temperature back during the day which could save even more natural gas usage.

  • Baseline (2008) - Therms per Heating Degree Day = 0.1097
  • Today (2012) - Therms per Heating Degree Day = 0.0559
  • 49% Reduction in Natural Gas Used for Heating!

Today we are using about HALF of the Natural Gas to heat our home (per Heating Degree Day) that we did in 2008! The R-50 attic insulation made the greatest efficiency improvement, followed by three air-sealing projects, and most recently by the thermostat. The programmable thermostat also has the shortest estimated payback period of the improvements we've made.

Can we do more to make our home more energy efficient? Yes, more projects are coming. Stay tuned!

More Info:

Bimetal (Mercury Switch) Thermostat

Heating Degree Day

Weather Underground (click 'History Data' at bottom of page to get Heating Degree Day data)

$25 Thermostat vs. $250 Thermostat

The Rugged Individual vs Fossil Fuels

Heating Bill Before and After Attic Insulation