Need a straight-shooting guide to emergency light voltages and Emergency Light Voltage Drop? This spoke walks through system voltage (6V/12V/24V), wire sizing, and practical field math so your remote heads stay bright—even on long runs. You’ll learn how voltage, current draw, and conductor size impact low-voltage emergency lighting circuits and overall egress performance. For a broader overview of code, fixture types, and maintenance, see the Emergency Lighting Guide. When you’re ready to compare units, browse the parent collection: Emergency Lights.
Emergency Light Voltage
Most standalone emergency light units operate on 6 volts DC. The building’s 120/277V AC is rectified to low-voltage DC for battery charging and emergency operation. Larger installations—especially when powering multiple remote heads—often rely on 12V or 24V DC systems to improve efficiency and reduce Emergency Light Voltage Drop. Higher system voltage means lower current for the same wattage, making long runs more stable and keeping LED heads bright. For related electrical context on signage circuits, see Exit Signs Voltage & Wattage Explained.
Understanding Voltage Drop
Any conductor has resistance, so voltage falls as current travels over distance. Short wiring distances cause only minor loss, but long-run circuits—common in hallways, warehouses, and garages—can see meaningful emergency lighting voltage drop. Excessive drop shows up as dim remote heads or uneven egress illumination. Designers typically target ≤ 5% voltage drop to preserve brightness and meet UL 924 nighttime visibility expectations. Selecting thicker copper (lower AWG numbers) or using higher system voltage helps maintain stable output.
Calculating Voltage Drop
You can compute drop with Ohm’s Law, but quick reference tables are faster. The table below shows approximate % voltage drop per 100 ft for common wire gauges at several load currents (assuming a 6V DC system). These values scale linearly with distance and provide a reliable baseline when planning emergency light wiring distance, remote-head load sizing, or troubleshooting dim fixtures.
| Wire Gauge | 0.5 A | 1 A | 2 A | 4 A | 10 A |
|---|---|---|---|---|---|
| 10 | 0.10% | 0.20% | 0.40% | 0.80% | 2.00% |
| 12 | 0.16% | 0.32% | 0.64% | 1.27% | 3.18% |
| 14 | 0.25% | 0.50% | 1.01% | 2.02% | 5.04% |
| 16 | 0.40% | 0.80% | 1.60% | 3.20% | 8.00% |
| 18 | 0.64% | 1.27% | 2.54% | 5.08% | 12.71% |
| 20 | 1.01% | 2.02% | 4.03% | 8.07% | 20.17% |
| 22 | 1.60% | 3.20% | 6.40% | 12.81% | 32.02% |
Formulas: Amps, Volts, Watts
Use these formulas when sizing remote head loads or estimating Emergency Light Voltage Drop:
- Watts = Volts × Amps
- Volts = Watts ÷ Amps
- Amps = Watts ÷ Volts
Example: a 6V emergency lamp with a 9W head draws 1.5A (9 ÷ 6). Two 9W heads total 18W, or 3A. LED remote heads (1–5W) dramatically reduce current—and therefore voltage drop—compared to legacy incandescent lamps (7–12W), which is why modern systems perform better on long runs.
Voltage Drop Examples
Scenario 1: One 12W remote head at 300 ft on 6V draws 2A. 18 AWG yields about 7.6% drop (too high). Upsize to 16 AWG and you’re ~4.8% (acceptable), improving both brightness and emergency runtime.
Scenario 2: Same lamp and distance on 24V draws only 0.5A. 18 AWG is ~1.96% at 300 ft—well within target. Even 22 AWG stays just under 5% (~4.8%). Higher-voltage systems are the simplest fix for long-run emergency lighting performance.
Scenario 3: A 25W remote at 300 ft on 24V draws ~1.04A. 18 AWG is ~3.1%, and you could run ~475 ft before hitting ~5%. This illustrates why many installers prefer 24V when multiple remote heads share the same circuit.
Need to verify runtime too? Use our Battery Runtime & Load Calculator. For a broader comparison of emergency-only fixtures vs. ambient exterior illumination strategies, see Emergency Lights vs. Wall Pack Lights.
Conclusion
Choosing the right system voltage and wire gauge is the fastest way to control Emergency Light Voltage Drop and ensure predictable performance. Higher-voltage systems (12/24V) handle long distances more gracefully because they reduce current, while 6V systems require thicker wire or shorter runs. When planning layouts, document your load, estimate drop, and always verify light levels during a nighttime walkthrough.
Need a straightforward, code-ready solution? Explore our Emergency Lights to find UL 924 fixtures matched to your voltage, run length, and environment. For onboarding or a quick refresher, pair this article with the Emergency Lighting Guide—it covers the big-picture code basics while this page tackles voltage-drop details.
Disclaimer: This article is for general educational purposes only and does not replace a stamped design, site-specific calculations, or the requirements of your local authority having jurisdiction (AHJ). Always verify wiring methods, conductor sizing, and Emergency Light Voltage Drop with the fixture manufacturer’s documentation, the NEC, and a licensed design professional before installing or modifying any emergency lighting system.