DE-2540 -- Temperature Setback and Energy Savings in Buildings Heated by Heat Pumps PDF

By comparing the thermal power loss of a building with the thermal power supplied by the heating system, one can derive simple expressions for the energy/cost savings that result from nighttime temperature setback. The special case of the heat pump is examined in which energy delivered by the heat pump has one unit cost while the energy delivered by the heat pump's auxiliary electric resistance heaters has a higher unit cost. In this case, it is shown that temperature setbacks of less than approximately l-hr duration can actually result in an increase in the energy consumption when compared·to the consumption with no reduction. Quantitative expressions are derived and evaluated for a range of operating conditions.