Motion Sensor Payback
Estimate savings from replacing an always-on light with a motion sensor.
About Motion Sensor Payback
A motion sensor cuts the same wattage's runtime from many hours to a few minutes a day. Comparing the yearly costs before and after gives the payback on the sensor. Outdoor and closet lights left on are a constant drain, so a cheap sensor investment recovers quickly through reduced electricity.
Formula
Motion Sensor Payback
Payback = sensor cost / annual savings
- on time
- How long the light runs with the sensor
Worked example
With the default values below, Motion Sensor Payback returns Annual Cost Before of $17.52. Change any input above and every figure here is recalculated in your browser.
Inputs used
- Light wattageminimum 0 watts
- 40 watts
- On time with sensorminimum 0 min/day
- 10 min/day
- On time without sensorminimum 0 hours/day
- 8 hours/day
- Electricity rateminimum 0 $/kWh
- 0.15 $/kWh
- Sensor costminimum 0
- 25
Results
- Annual Cost Before
- $17.52
- Annual Cost After
- $0.37
- Annual Savings
- $17.16
- Payback Period
- 1.46 yr
Step by step
- 1Values used
- 2Motion Sensor Payback
- 3Annual Cost Before= 17.52
- 4Annual Cost After= 0.37
- 5Annual Savings= 17.16
- 6Payback Period= 1.46 yr
Assumptions and limits
- The result is derived only from the 5 inputs listed above. Anything not among them is not part of the calculation.
- In particular, this calculator does not take inflation, tax or compounding frequency into account.
- Figures are rounded for display to 2 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.
Frequently Asked Questions
How is Motion Sensor Payback calculated?
Payback = sensor cost / annual savings A motion sensor cuts the same wattage's runtime from many hours to a few minutes a day. Comparing the yearly costs before and after gives the payback on the sensor.
Why does Motion Sensor Payback matter?
Outdoor and closet lights left on are a constant drain, so a cheap sensor investment recovers quickly through reduced electricity.
What values do I need to enter?
This calculator takes 5 inputs: Light wattage, On time with sensor, On time without sensor, Electricity rate, Sensor cost. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.