Emergency Lighting Calculator

Emergency lighting systems must keep exit routes illuminated during a power failure — building codes require batteries sized to last a minimum duration, and undersizing puts lives at risk. Enter your number of emergency fixtures, fixture wattage, exit sign count, and exit sign wattage, then select your required runtime, battery voltage, battery type, and ambient temperature. The Emergency Lighting Calculator returns the required battery capacity in Ah, along with total system load, total energy required, derated capacity, and actual runtime.

W
W
°C

Temperature affects battery capacity

Accounts for battery degradation over time

Results

Required Battery Capacity

--

Total System Load

--

Total Energy Required

--

Derated Capacity

--

Actual Runtime

--

More Electrical & Electronics Tools

Frequently Asked Questions

What are the NEC Article 700 and NFPA 101 requirements for emergency lighting?

NEC Article 700 and NFPA 101 require emergency lighting to provide minimum 1 foot-candle (10.8 lux) illumination for 90 minutes minimum. Systems must automatically activate within 10 seconds of power failure and maintain illumination along egress paths.

How do you calculate emergency lighting battery capacity?

Battery capacity is calculated by determining total load (watts), multiplying by required runtime (hours), dividing by system voltage, then applying derating factors for temperature and aging. The formula is: Capacity (Ah) = (Total Load × Runtime) / (Voltage × Derating Factors).

What are the differences between self-contained and central battery systems?

Self-contained units have individual batteries in each fixture, making installation easier but requiring more maintenance. Central battery systems use one large battery bank to power multiple fixtures, offering better monitoring and maintenance but higher upfront costs.

How does temperature affect emergency lighting battery performance?

Cold temperatures reduce battery capacity significantly - typically 50% capacity loss at 0°C for lead-acid batteries. High temperatures accelerate aging and can cause thermal runaway. Temperature derating factors must be applied to ensure adequate capacity.

What is the battery aging factor and why is it important?

The aging factor accounts for battery capacity loss over time due to charge/discharge cycles and chemical degradation. New batteries may have 100% capacity, but after 3-5 years, capacity drops to 70-80%. Using 0.8 aging factor ensures reliable operation throughout battery life.

How do LED emergency lighting systems differ from traditional systems?

LED emergency lights consume significantly less power (typically 3-10W vs 20-40W for incandescent), allowing smaller battery systems and longer runtime. They also have longer lamp life (10+ years vs 1-2 years) and better light output stability over the discharge cycle.

What are the testing and maintenance requirements for emergency lighting?

Monthly 30-second functional tests and annual 90-minute duration tests are required. Central battery systems need quarterly battery inspections, annual capacity tests, and replacement every 5-10 years depending on type. Self-contained units typically need battery replacement every 3-5 years.

Can I power remote heads from any emergency light fixture?

Only fixtures specifically designed as 'remote capable' can power additional remote heads. The main fixture's battery must be sized for the total load of the fixture plus all remote heads. Check manufacturer specifications for maximum remote head capacity and wiring distance limitations.