Occupancy Sensor Savings Estimator

Lighting Specification

Number of luminaires (fixtures)

Number of lamps per luminaire

Wattage of each lamp (bulb) (watts)

Ballast Multiplier (%)

Calculate total wattage

Total wattage of lamps connected to occupancy sensor watts

Operational Characteristics

Total operating hours

Area occupancy rate (%)

Average annual energy rate ($/kWh)

Average annual demand rate ($/kW)

Cost to install occupancy sensor ($)

Savings and Payback

Calculate Savings and Payback

Cost to operate lights without occupancy sensors ($)

Cost to operate lights with occupancy sensors ($)

Annual energy cost savings ($)

Simple payback period years

Instructions

The Occupancy Sensor Savings Estimator is intended to estimate the savings associate with utilizing occupancy sensors to turn off lights in areas that are unoccupied. The estimator may be used for each seperate lighting circuit or group of circuits with similar operating characteristics. Circuit wattage may be calculated by entering the required data, or can be entered directly if the wattage is already known. Ballast wattage and efficiency are not estimated with the lighting specification, but this wattage may be manually added to the total wattage field for a more accurate estimate.

Inputs

Number of luminaires - the number of lighting fixtures connected to the occupancy sensor.
Number of lamps per luminaire - the number of bulbs in each fixture.
Wattage of each lamp - the wattage of each light bulb.
Ballast multiplier - compensates for the wattage used by the ballast. Example: for a 400 W Metal Halide lamp, use 10% to show that the ballast consumes 40 Watts.
Total wattage of lamps connected to occupancy sensor - the total wattage of the lights that will be controlled by the occupancy sensor. You can use the above fields to calculate this wattage, or enter it directly.
Total operating hours - the annual number of hours that the lights would be left on if there was no occupancy sensor in the circuit.
Area occupancy rate - the percentage of time that people occupy the space. This is the percentage of time that the lights will be on when the occupancy sensor is installed.
Average annual energy rate - the average annual marginal cost of energy per kWh. In most cases, occupancy sensors will not reduce peak demand, so it is important that marginal energy cost be used instead of average or aggregate energy cost.
Average annual demand rate - the average annual marginal cost of demand per kW peak. Enter zero if an average or aggregate energy cost was used above. This will make the calculation less accurate.
Cost to install occupancy sensor - the total cost, including material and labor, to install the occupancy sensor.

Outputs

Cost to operate lights without occupancy sensors - the cost of energy plus demand charges to operate the lights for the full number of operating hours.
Cost to operate lights with occupancy sensors - the cost of energy plus demand charges to operate the lights for only the percentage of time that the space is occupied.
Annual savings - the difference in the two costs.
Simple payback period - the ratio of savings to installation cost.

Contact the Arkansas Industrial Energy Clearinghouse if you need assistance with this calculator.