Emergency Light Voltages – Understanding 6V, 12V & 24V Systems

Emergency lighting operates using a combination of AC and DC power. While the standard voltage supplied by a building is 120V AC, emergency lights convert this to low-voltage DC using a built-in transformer. Most emergency lighting systems run on 6V, 12V, or 24V DC, depending on the fixture type and application.

Emergency Light Voltage and Wattage Explained

In this article:

• How Emergency Light Voltages Work
• Benefits of Higher Voltage Emergency Lighting
• Emergency Light Wattage Options
• Why Voltage Matters for Remote Heads
• How to Calculate Voltage Drop
• Configurable Steel Emergency Lights
• Additional Resources

How Emergency Light Voltages Work

When AC power flows into an emergency lighting unit, it passes through a transformer and a rectifier, converting it to low-voltage DC. This current then powers the lamp heads or charges the internal battery. The DC voltage used — 6V, 12V, or 24V — varies by model and determines the fixture’s light output and battery performance.

Benefits of Higher Voltage Emergency Lighting

Higher voltage systems (like 24V DC) offer greater brightness and longer cable runs to remote heads without significant voltage drop. This makes them ideal for large commercial or industrial spaces where fewer but more powerful fixtures are preferred.

• 6V: Most common and cost-effective for general use
• 12V: Mid-range brightness with better range than 6V
• 24V: High output for large or multi-head systems

Higher voltage systems also support larger battery capacities and more powerful lamp heads, making them suitable for extended runtime or high-output applications.

Shop 6V, 12V & 24V Emergency Lights

Emergency Light Wattage Options

In addition to voltage, lamp wattage determines how bright your emergency lighting will be. Common lamp head wattages include:

• 7.2W
• 8W
• 9W
• 10W
• 12.5W
• 18W
• 25W

Higher wattage equals greater light intensity. For example, a 25W lamp head provides significantly more coverage than a 7.2W head. However, wattage must be balanced with battery capacity and system voltage (a higher wattage lamp will drain a small battery faster).

Why Voltage Matters for Remote Heads

When using remote heads with your emergency light, voltage drop becomes a key factor. The higher the system voltage, the farther you can run cabling to remote fixtures without noticeably reducing brightness. In other words, a 24V system can deliver power over longer distances than a 6V system because the relative loss is smaller. Understanding voltage drop is essential for proper placement and performance across longer cable runs.

How to Calculate Voltage Drop

Calculating the voltage drop in an emergency lighting circuit ensures that remote heads stay bright and within code requirements. Voltage drop is the gradual loss of voltage that occurs as current flows through a wire’s resistance. If the drop is too great, a remote lamp can appear dimmer or not perform properly. Fortunately, you can determine voltage drop with a few simple tools and steps, then plan your installation to minimize it.

Tools Needed for Safe Voltage Drop Calculation

• Digital multimeter: For measuring voltage levels at the source and at remote lights (useful if you want to verify the actual drop later).
• Voltage drop calculator or wire gauge chart: Helps estimate drop based on wire length, gauge, and current.
• Measuring tape: To measure the length of wire runs (distance from the emergency unit to remote head).
• Power shut-off capability: Ensure you can turn off the circuit breaker supplying the emergency light before working on any wiring.
• Protective gear: Insulated gloves and safety glasses for personal protection when handling electrical components.

1. Determine the current draw (amps): Find the wattage of the emergency lamp or remote head (from its bulb or LED specification) and note the system voltage (e.g., 6V, 12V, 24V). Use the relationship Watts = Volts × Amps to calculate the amperage. Rearranging gives Amps = Watts ÷ Volts. For example, a 6V lamp with a 9W bulb draws 1.5 A (since 9 W ÷ 6 V = 1.5 A). A higher wattage or lower voltage will result in a higher current draw.
2. Measure the wire run length and identify the wire gauge: Measure the distance from the emergency light’s power source (usually its battery or output terminals) to the remote head’s location. Use the one-way distance for calculations, but remember the circuit is round-trip (outbound and return wire). Identify the gauge of the wire used or planned for the run. Wire gauge is a measure of thickness: a larger diameter wire (like 12 AWG) has lower resistance than a smaller diameter wire (like 18 AWG). Thinner wires (higher gauge numbers) will cause more voltage drop for the same current. Make sure you know the wire gauge so you can account for its resistance. (If unsure, many emergency light remote head kits use 18 AWG by default.) It’s helpful to use an online voltage drop calculator or reference chart at this stage to see how your wire gauge, length, and current will interact.
3. Calculate the expected voltage drop: Using the current from step 1 and the details from step 2, estimate the voltage drop. The basic formula for DC voltage drop is V_drop = I × R_total, where R_total is the resistance of the round-trip wire length. In practical terms, you can input the wire gauge (which gives you resistance per foot), the one-way distance (in feet), and the current (amps) into a voltage drop calculator to get the drop in volts and as a percentage of your system voltage. As a rule of thumb, try to keep voltage drop under about 5% of the system’s nominal voltage. (Building codes often recommend a maximum 5% voltage drop to ensure equipment operates correctly.) For instance, consider a 6V emergency light system with a remote head 300 feet away. Suppose the remote lamp is 12 W. From step 1, the current draw would be 2 A (12 W ÷ 6 V = 2 A). If you ran that remote on standard 18 AWG wire over 300 ft, the voltage drop would be roughly 7.6% of the 6 volts, which is beyond the safe limit. In fact, at 2 A load, 18-gauge wire loses about 2.54% voltage per 100 feet, so over 300 feet that’s ~7.6% drop. This would likely make the remote head noticeably dim. However, if you used a thicker 16 AWG cable for that run, the drop would fall to roughly 4.8%, which is within acceptable range (under the 5% guideline).
4. Implement solutions to reduce drop (if needed): If your calculation shows a voltage drop above ~5%, you should adjust your design to reduce it. One option is to use a wire with a larger diameter (lower AWG number) to decrease resistance and thus reduce the drop. For the example above, upgrading from 18 AWG to 16 AWG wire brought the drop down into safe limits. Another approach is to choose a higher-voltage emergency light system if possible (for example, using a 12V or 24V unit instead of 6V for long cable runs). A higher supply voltage means a lower current for the same wattage, which in turn yields a smaller voltage drop. In our 12 W remote head scenario, using a 24V system instead of 6V changes the current draw to 0.5 A (12 W ÷ 24 V) – only one-quarter of the 6V system’s current. That 0.5 A through 300 ft of 18 AWG wire would result in about a 2% voltage drop, a dramatic improvement. In fact, even using a thinner 22 AWG wire on a 24V system in that scenario would still keep the drop around 4.8% over 300 ft. The key is to either reduce the resistance of the wiring or reduce the current in the circuit (by raising voltage or lowering wattage) until the drop is within acceptable limits.
5. Verify and test the setup: After implementing any changes, it’s important to verify the voltage drop under real conditions. First, ensure all wiring is properly connected and **restore power** to the emergency light system. Then test the system under battery power (you can do this by cutting AC power to trigger an emergency mode, or using the unit’s “test” button if available). Using a multimeter, measure the voltage at the emergency light’s battery terminals (or output) and then measure the voltage at the remote head while it’s illuminated under load. Subtract the two readings to find the actual voltage drop, and calculate what percentage of the total voltage that drop represents. This measured drop should be close to your earlier calculation and ideally under 5%. Finally, conduct a full functionality test: with AC power restored, ensure the unit charges and that the remote heads light up properly when power is cut. This confirms that your emergency lighting will perform as expected during an outage. If you are uncertain about any step or the results, consider consulting a licensed electrician for assistance and to ensure compliance with electrical codes.

Configurable Steel Emergency Lights

Unlike thermoplastic models that come with fixed voltage and wattage, steel emergency lights are fully customizable. You can select your preferred system voltage, battery capacity, lamp wattage, and even remote head configurations to suit your application. For example, in a large facility you might choose a 24V steel unit with a higher-capacity battery to support long cable runs and multiple high-wattage remote heads. Despite similar outward appearances, each steel unit can be tailored for vastly different power specs and lighting needs, ensuring you get the right performance for your environment.