You calculate the payback period of a lighting control system with a simple formula: investment divided by annual cost savings. The annual savings result from installed load, operating hours, savings rate and electricity price. In the example in this guide, a hall with 100 LED high-bay luminaires at 150 W saves around 45,000 kWh per year at a 60 % savings rate. In halls with long operating hours lighting control therefore often pays back quickly; in offices it usually takes longer. The calculations below are examples with explicitly stated assumptions, not Building Robotics prices.
The formula
Simple (static) payback is usually sufficient for an investment decision:
Annual savings (kWh) = number of luminaires × wattage per luminaire (kW) × operating hours per year × savings rate
Annual cost savings (€) = annual savings (kWh) × electricity price (€/kWh)
Payback period (years) = investment (€) / annual cost savings (€)
The savings rate combines all control functions: occupancy, daylight and constant light output. How to derive this rate from individual factors, why the factors are multiplied rather than added, and how to account for standby consumption and net present value is explained in Calculating lighting control savings. This guide focuses on two worked examples and the question of what investment is worthwhile.
Example 1: warehouse with 100 LED high-bay luminaires
Assumptions:
- 100 LED high-bay luminaires at 150 W system power each, already with dimmable 0-10 V drivers
- two-shift operation, lights currently on for around 5,000 hours per year
- assumed electricity price €0.22/kWh net
- savings rate from occupancy and daylight control as a range of 40 %, 60 % and 75 %
Step 1: baseline consumption
| Step | Formula | Result |
|---|---|---|
| Installed load | 100 × 0.15 kW | 15 kW |
| Baseline consumption | 15 kW × 5,000 h | 75,000 kWh/a |
| Current electricity cost | 75,000 kWh × €0.22/kWh | €16,500/a |
Step 2: annual savings
| Savings rate (assumption) | Energy saved | Cost savings per year | Per luminaire per year |
|---|---|---|---|
| 40 % | 30,000 kWh | €6,600 | €66 |
| 60 % | 45,000 kWh | €9,900 | €99 |
| 75 % | 56,250 kWh | €12,375 | approx. €124 |
The range is deliberately wide. In warehouses with rarely used aisles and rooflights, higher values are possible: as a guideline from our projects, sensors alone save more than 60 %, and the potential goes up to 92 %. In high-traffic areas such as picking or goods-in the rate is lower.
Step 3: payback with your quoted price
The investment depends on the project. Divide your quoted price by the annual cost savings from step 2 – the result is the simple payback period in years.
The other way round: what investment is affordable?
Often the question is reversed: how much may the lighting control cost per luminaire to pay back within a target period?
Affordable investment per luminaire = cost savings per luminaire per year × target payback period
| Savings rate | Target: 3 years | Target: 5 years |
|---|---|---|
| 40 % | €198 | €330 |
| 60 % | €297 | €495 |
| 75 % | €371 | €619 |
If a quote is below these values, the target is met within the assumptions. This lets you assess quotes quickly without redoing the calculation.
Example 2: office floor with 200 luminaires
Assumptions:
- 200 LED office luminaires at 35 W each, dimmable drivers in place
- lights currently on for around 3,000 hours per year, from the first employee to the cleaners in the evening
- assumed electricity price €0.22/kWh net
- savings rate as a range of 30 %, 45 % and 55 %
| Step | Result |
|---|---|
| Installed load | 200 × 0.035 kW = 7 kW |
| Baseline consumption | 7 kW × 3,000 h = 21,000 kWh/a |
| Savings at 30 % | 6,300 kWh = €1,386/a |
| Savings at 45 % | 9,450 kWh = €2,079/a |
| Savings at 55 % | 11,550 kWh = €2,541/a |
Affordable investment per luminaire for a target payback period (cost savings per luminaire and year × target period):
| Savings rate | Target: 3 years | Target: 5 years |
|---|---|---|
| 30 % | €21 | €35 |
| 45 % | €31 | €52 |
| 55 % | €38 | €64 |
The result is honest: in offices the wattage per luminaire is low and operating hours are shorter, so electricity savings alone pay back more slowly than in a hall. That is not an argument against lighting control in offices, but for a complete view:
- Legal duty: § 56 of the German Building Modernisation Act (GModG) requires automatic lighting control by 31 December 2029 in non-residential buildings with a heating, air-conditioning or combined ventilation system above 70 kW. The question is then not whether, but how economically. General information, not legal advice.
- Occupancy data: occupancy data shows which spaces are actually used, which with hybrid working is often worth more than the electricity, see Energy monitoring and occupancy data.
- Building automation: lighting control data can be used for heating and ventilation. Building automation of at least class B according to DIN V 18599-11 is funded at 15 % under BEG EM (as of October 2026).
- Combination with refurbishment: if the space is being refurbished anyway, for example for a new tenant, the additional cost of the control falls.
How strongly does each variable matter?
All variables enter the savings linearly, which gives simple rules of thumb:
- Operating hours: double the operating time means double the savings and half the payback period. Three-shift operation pays back correspondingly faster.
- Electricity price: if the price rises by 20 %, the payback period falls by around one sixth.
- Wattage per luminaire: high-wattage high-bay luminaires save considerably more per sensor than office luminaires.
- Savings rate: it depends on usage, not only on technology. Calculating zones separately, such as aisles, traffic routes and picking areas, gives more realistic values.
What the simple calculation leaves out
Simple payback is deliberately basic. A complete assessment also includes:
- Standby consumption of the sensors: sensors and wireless nodes run around the clock. Their consumption is small but belongs in the calculation; the power draw is in each datasheet.
- Longer luminaire life: dimmed luminaires that are switched off when not needed reach their rated life later.
- Cooling load: in air-conditioned buildings, less heat from lighting reduces cooling energy.
- Net present value: if you want to include financing costs, also calculate the net present value, as shown in Calculating lighting control savings.
What determines the investment itself, from driver interface to mounting height and work during operation, is explained in What does a lighting control system cost?.
Conclusion
The payback of a lighting control system follows from the investment and the annual cost savings. In the example hall with 100 luminaires at 150 W, 5,000 operating hours and €0.22/kWh, annual savings range from €6,600 to €12,375 depending on the rate. In offices the figures are lower, and the legal duty, occupancy data and building automation count as well. Calculate with your own numbers and compare quotes with the affordable investment per luminaire.
How we can help
Our focus is retrofitting: we turn existing LED luminaires with dimmable 0-10 V or DALI drivers into smart lighting with sensors and app-based lighting management – without new luminaires and without new control cables. Details under Retrofit.
We calculate the economics with your luminaire data, operating hours and electricity price and show you the planned sensors in advance in Sensora. Installation is usually carried out by us, or by your own electrical contractor if you prefer. Every project includes the AU-Manager, so occupancy detection, zoning and monitoring are included and the savings become measurable. Get in touch via our contact page.
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Frequently asked questions
How do I calculate the payback of lighting control?
Divide the investment by the annual cost savings. The savings result from the number of luminaires, wattage per luminaire, operating hours, savings rate and electricity price.
How quickly does lighting control pay back in a warehouse?
That depends on operating hours, luminaire wattage, electricity price and investment. In the example with 100 high-bay luminaires at 150 W, 5,000 hours and €0.22/kWh, annual savings range from €6,600 to €12,375. Divide your quoted price by this figure to get the payback period in years.
Why does lighting control pay back more slowly in offices?
Office luminaires have lower wattage and shorter operating hours than high-bay luminaires, so the electricity saved per luminaire is smaller. Include occupancy data, the duty under § 56 GModG and the use for building automation in the assessment.
What savings rate should I assume?
Use a range rather than a single value. As a guideline from our projects, sensors alone save more than 60 %, and the potential goes up to 92 %. Be more conservative for high-traffic areas and offices.
How much may lighting control cost per luminaire?
Multiply the annual cost savings per luminaire by your target payback period. If a luminaire saves €99 per year, as in the example, up to €297 per luminaire would be affordable for a three-year target.
