Savings Estimates from using a programmable thermostat
Consumers are often advised that installing a programmable thermostat can save them anywhere from 10 to 30% on the space heating and cooling portion of their energy bills. While reliant on proper use of the programmable thermostat, such savings are easily true in theory; however, there needs to be more field-tested data to better substantiate savings claims.
Analyses from recent field studies have suggested that programmable thermostats may be achieving considerably lower savings than their estimated potential. In particular, a study from the Energy Center of Wisconsin showed no statistical difference in heating intensity among their sample of single-family houses when comparing households with programmable thermostats and those without. These studies suggest that, in practice, programmable thermostats may often not be saving the 10%-30% as claimed. However, findings from the Wisconsin study are not conclusive and the research itself has some shortcomings (e.g., consumers were using an older generation of programmable thermostats).
A variety of statistical and anecdotal evidence indicates possible reasons as to why discrepancies between predicted and actual savings may exist. In particular it is thought that:
1) Many households (perhaps 30% or higher) with programmable thermostats may be unable, unwilling, afraid, uninterested, or otherwise reluctant to deploy default programs or to create or deploy custom programs;
2) Many households (about 50%) set back or set up their thermostats manually, thus leaving less savings possibilities to be garnered by a programmable thermostat;
3) The automatic program used with the thermostat may not be any more conservative than use of manual thermostats setback or setup by hand;
4) Many consumers have mental models of heating and cooling that lead them to believe they will not save energy from setting up or setting back other than long periods of time.
By better understanding and addressing these important issues, manufacturers may be able to increase customer satisfaction and market share, while legitimately claiming substantial savings achievable from using programmable thermostats as prescribed.