Lighting Control Load Calculator

Example Data Table

Use this as a quick reference for typical entries.

Formula Used

• Zone connected load (W) = Fixtures × W/fixture
• Zone effective load (W) = Zone connected × (Dimming % ÷ 100) × Zone diversity
• Average demand (W) = (Σ Zone effective) × Global diversity × Control overhead + Standby W
• Peak demand (kW) = (Average W ÷ 1000) × Demand factor
• Apparent power (kVA) = Peak kW ÷ Power factor
• Current (A):
  • Single-phase: I = Peak kW × 1000 ÷ (V × PF)
  • Three-phase: I = Peak kW × 1000 ÷ (√3 × V × PF)
• Annual energy (kWh) = Average kW × Hours/day × Days/year
• Annual cost = Annual kWh × Cost per kWh

How to Use This Calculator

1. Set the supply phase, voltage, and power factor.
2. Choose how many lighting zones you want to model.
3. For each zone, enter fixtures, wattage, dimming, and diversity.
4. Add standby/controller watts if your design requires it.
5. Enter operating hours, annual days, and the energy cost.
6. Press Calculate to see results above the form.
7. Use Download CSV or Download PDF for records.

Lighting Control Load Planning Guide

1) Why controlled lighting loads matter on site

Lighting controls can reduce real demand, but they also introduce new design assumptions. A zone that is “installed” at 3.0 kW may operate closer to 1.8 kW when dimmed and diversified. Quantifying that difference supports feeder sizing, panel schedules, and coordination with the BMS.

2) Zone data that drives results

Start with fixtures and wattage to establish connected load. Then apply dimming percentage to reflect typical light levels, not maximum output. Zone diversity accounts for occupancy patterns; open offices may run at 0.80–0.90, while meeting rooms often sit around 0.40–0.70.

3) From kW to kVA and current

Electrical infrastructure is sensitive to power factor. The calculator converts peak kW into apparent power (kVA) using PF, then estimates current using supply voltage and phase selection. This helps compare demand against breaker ratings and distribution limits, especially where mixed loads share the same upstream circuits.

4) Energy and cost benchmarks

Annual energy is based on average kW multiplied by operating hours and days. For example, 2.2 kW average running 10 hours per day for 300 days yields about 6,600 kWh per year. Multiply by your tariff to create a defensible operating-cost line item for stakeholders.

5) Practical factors for commissioning

Global diversity and control overhead factors let you align estimates with measured performance. Add standby/controller watts for gateways, sensors, and power supplies. During commissioning, compare metered values to calculated averages and tune dimming presets and schedules to close gaps.

FAQs

1) What is the difference between connected load and demand?

Connected load is fixtures × wattage at full output. Demand reflects how the system actually operates after dimming, diversity, overhead, and standby power are applied.

2) When should I use zone diversity versus global diversity?

Use zone diversity for area-specific behavior, like meeting rooms or corridors. Use global diversity to reflect site-wide scheduling, staggered occupancy, or portfolio assumptions after all zones are summed.

3) What does the control overhead factor represent?

It is a planning multiplier to cover controller losses, power supply inefficiency, and conservative allowances. Keep it at 1.00 unless your standard practice requires a margin.

4) Why does power factor affect current and kVA?

Lower power factor increases apparent power for the same real power. That can raise current and influence equipment sizing, even if the real kW demand stays unchanged.

5) How do I model automatic daylight dimming?

Reduce the dimming percentage for zones with daylight harvesting, such as perimeter offices. If daylight performance varies, use a conservative seasonal average and validate with submetering later.

6) Does this calculator replace an electrical design review?

No. It supports early planning and documentation. Final designs should follow local codes, manufacturer data, and verified measurements for the specific luminaires and control gear.

7) Why might peak demand be higher than average demand?

Peak demand uses a demand factor to represent periods of higher activity, such as full occupancy, events, cleaning, or manual overrides. It helps size infrastructure for realistic worst-case operation.