How to Size Explosion Proof Solar Power Systems for Hazardous-Area Lighting

To size an explosion proof solar power system for hazardous-area lighting, calculate the lights’ daily energy use, estimate the solar array needed to replace that energy, and select a battery that can cover the required period without sunlight. Then verify that every component installed in or near the classified area is suitable for the site’s hazardous-area classification and environmental conditions. The right design depends on actual fixture wattage, operating hours, local solar resource, autonomy requirements, and system losses—not on a generic kit size.

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We recommend preparing a load and site data sheet before requesting a quotation. The example calculations below show how to create a preliminary estimate; they are not a substitute for a site-specific electrical design or hazardous-area review. A qualified project engineer should confirm final component selection, wiring, protection, and installation requirements.

Key Takeaways

• Start with the total lighting load in watt-hours per day, including every fixture and its operating schedule.
• Size the PV array against the site’s conservative solar resource and realistic system losses.
• Size the battery for required autonomy, usable capacity, voltage, temperature, and battery-management limits.
• Check hazardous-area suitability for the complete installation, not only the LED light fixture.
• Share operating and site details with your supplier so the preliminary design can be reviewed before procurement.

Step 1: Define the Lighting Load

List each light, its rated electrical input, quantity, and expected hours of operation per day. Use the fixture’s input wattage rather than its lumen output, since watts are the electrical load the solar system must supply. If lights are controlled by timers, sensors, or a control system, use the planned operating schedule and account for periods when multiple fixtures run together.

Calculate Daily Energy Consumption

Multiply the wattage of each load by its daily operating hours, then add the results. The basic formula is: daily energy (Wh/day) = load power (W) × operating time (h/day). For example, two 60 W lights operating for 12 hours each day consume 1,440 Wh/day before system losses.

Include other equipment powered by the same system, such as controls, communications devices, or heaters, if applicable. Check whether the fixture driver or control equipment has a power factor or surge characteristic relevant to the design, especially for an AC system. If the schedule varies by season or shift, calculate the highest expected daily load rather than relying only on an average.

Step 2: Estimate the Solar Array

The PV array must generate enough energy to serve the daily load and compensate for losses in charging, wiring, conversion, and operating conditions. A preliminary estimate is: PV array watts = daily energy (Wh/day) ÷ (peak sun hours per day × overall system efficiency). Use a conservative solar-resource value for the project location and season of concern, rather than a best-month average.

Illustrative PV Sizing Example

For the example load of 1,440 Wh/day, assume 4 peak sun hours per day and an illustrative overall efficiency factor of 0.70. The calculation is 1,440 ÷ (4 × 0.70), which gives approximately 514 W of PV capacity. This is a planning example only: actual array sizing should account for local solar data, panel orientation, shading, temperature, dust, and the chosen equipment.

When the system must maintain lighting through a difficult season, design around the weaker solar period and evaluate whether the array can recover the battery after low-sun days. A designer may increase array capacity or adjust the operating plan, but the appropriate choice depends on the location and system architecture. Avoid selecting panels solely by matching their nominal wattage to the light load.

Step 3: Size the Battery for Autonomy

Autonomy is the number of days the battery must support the load when solar generation is insufficient. Confirm the required duration with the project owner, considering the consequences of lighting interruption and the availability of backup power. Battery capacity should be based on energy demand, system voltage, permitted depth of discharge, conversion losses, temperature, and manufacturer limits.

Illustrative Battery Calculation

For a DC load of 1,440 Wh/day, two days of autonomy, a 24 V battery, and an assumed usable fraction of 80%, a simple estimate is: battery capacity (Ah) = daily energy × autonomy days ÷ (battery voltage × usable fraction). The result is 1,440 × 2 ÷ (24 × 0.80), or 150 Ah, before considering additional design allowances or specific battery characteristics.

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This estimate is not a battery specification. If an inverter is used, include its efficiency and standby consumption; for a DC system, include relevant controller and wiring losses. Also check how the battery performs at the site’s minimum and maximum temperatures, and confirm that the selected battery-management system supports the intended charge and discharge conditions.

Step 4: Match the Electrical Architecture and Hazardous-Area Requirements

Decide whether the lighting system will operate on DC or AC, and confirm that the lights, controller, battery, and any inverter are compatible in voltage and current. An inverter may be needed for AC fixtures, but it adds conversion losses and another component to assess. Check cable lengths, voltage drop, protective devices, grounding or bonding requirements, and the system’s maximum charging and load currents with a qualified designer.

Hazardous-area suitability is a system-level concern. Confirm the site classification, gas or dust group where applicable, temperature class or maximum surface-temperature requirements, ambient temperature range, and local approval framework. A fixture’s suitability does not automatically establish that a battery enclosure, junction box, controller, inverter, or installation method is suitable for the same location.

Where possible, identify which equipment will be placed inside the classified area and which can be located in a safe area. The project’s responsible electrical or process-safety team should confirm whether that arrangement is permitted and what protection or approval is required. Do not assume that ordinary solar modules or electrical accessories are appropriate for installation in a hazardous zone.

Key Decisions Before You Request a Quote

Common Sizing Mistakes

• Using fixture lumens instead of input watts: Lumens describe light output, while watts determine electrical energy demand. Confirm the fixture’s actual input rating.
• Designing from annual-average sunlight: Averages can conceal seasonal shortfalls. Evaluate the location and period when dependable lighting is most important.
• Ignoring losses and operating conditions: Wiring, controllers, conversion, temperature, dust, and shading can affect delivered energy. Use defensible assumptions and have them reviewed.
• Choosing a battery by nominal capacity alone: Usable energy can differ from nominal energy because of discharge limits, temperature, and battery-management requirements.
• Checking only the light’s hazardous-area status: Review the proposed system layout and every component in the classified area with the responsible technical team.

Improve Reliability Before Finalizing the Design

Use a clear operating schedule and energy budget, and separate essential lighting from loads that can be shed if battery charge is low. Consider whether dimming, motion-based control, or staged operation is acceptable for the application; any control strategy must preserve required illumination and suit the site’s safety procedures. A lower energy demand can reduce the required PV and battery capacity, but only if the lighting outcome remains fit for purpose.

Plan for inspection and maintenance as well as initial operation. Confirm access to panels, battery enclosures, cable routes, and fixtures, and identify how the system will be checked after installation. For remote sites, discuss replacement access and component availability with suppliers before committing to an architecture.

How MASCO Can Support Your Sizing Review

As a manufacturer and supplier focused on LED explosion-proof lighting and related equipment, we can help buyers organize the lighting-side information needed for a project discussion. Share the fixture schedule, input voltage, operating hours, hazardous-area classification, location, mounting conditions, autonomy target, and any required approval framework. We can then review product and project requirements with you and clarify which information is needed for a system proposal.

Final PV, battery, and installation design should be confirmed by the project’s qualified solar and electrical professionals. Provide the supplier with drawings or a component list where available, and ask for a clear statement of design assumptions, component locations, and items that remain subject to engineering approval. This makes it easier to compare proposals on a consistent basis.

Conclusion: Size from the Load, Then Verify the Site

To size an explosion proof solar power system for hazardous-area lighting, calculate daily watt-hours, estimate PV capacity using conservative solar conditions and system losses, and select battery capacity for the required autonomy and usable energy. Then verify voltage compatibility, installation conditions, and hazardous-area requirements for every component in the proposed layout. The illustrative calculations in this guide provide a starting point, not a final design.

Your next step is to prepare a load schedule and share the project location, operating profile, autonomy requirement, and hazardous-area details with your supplier and engineering team. MASCO can support the lighting and product discussion for your project; contact us with those inputs to begin a practical, application-specific review.

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