24. Existing Building Energy Upgrade Project * with tax credits Description First Cost Annual Savings Payback Lighting Upgrade $65,000 $21,000 3.1 yr Install programmable thermostats $12,000 $8,500 1.4 yr Chiller Replacement $95,000 $27,000 3.5 yr Improve Boiler Combustion efficiency $1,500 $2,000 0.8 yr Insulate hot water pipes $3,000 $500 6.0 yr Install door thresholds $450 $140 3.2 yr Install Variable Speed Drives on fans $24,500 $9,500 2.6 yr Replace standard efficiency motors for chilled water pumping $2,300 $550 6.2 yr * Install 10 kW photovoltaic array $40,000 $1,600 25.0 yr Total $243,750 $70,790 3.4 yr