Across India, factories are rapidly adopting solar power, not just as a cost-cutting measure, but as a long-term strategic investment. Rising electricity tariffs, the pressure to reduce carbon emissions and the growing demand for sustainable manufacturing have all pushed industries to rethink how and from where they source their energy. For many businesses today, switching to solar is no longer optional; it has become essential for competitiveness, operational stability, and brand leadership.
Solar energy offers factories a powerful combination of benefits: lower electricity bills, protection against grid price fluctuations, reduced dependence on diesel generators, and significant cuts in carbon footprint. For many standalone factories, it is also a great way to utilise idle land or roof space and convert it into revenue-generating assets. As more industrial clusters modernise, solar has emerged as one of the most reliable and scalable pathways to cleaner, cheaper, and more resilient power.
But once a factory decides to go solar, one critical question always follows:
How much solar power does my facility actually need?
Sizing a solar plant isn’t guesswork. Factory energy consumption varies across shifts, machinery types, building design, and weather conditions. A perfectly sized solar system requires a detailed understanding of consumption patterns, roof feasibility, engineering constraints, and operational hours.
This blog breaks down exactly how factories can determine the right solar capacity, using a mix of technical insights, real-world examples, and FPEL’s engineering expertise.
Steps to Determine How Much Solar Your Factory Needs
Understanding Your Factory’s Power Consumption (kW vs kWh)
Every accurate solar design begins with understanding the difference between kW and kWh:
- kW (Kilowatt) is the power demand. It reflects how much load your equipment is drawing at a specific moment.
- kWh (Kilowatt-hour) is the energy consumed over time—this is what you see as “units” on your electricity bill.
Suppose your factory operates at a load of 300 kW for 10 hours. Your daily energy consumption becomes:
300 × 10 = 3000 kWh (or 3,000 units)
Solar sizing depends primarily on your daily and monthly kWh consumption and how much of it occurs during sunlight hours.
Calculate Required Solar System Size (Simple Formula)
You can roughly calculate solar capacity needed as:
Solar Capacity (kW) = Monthly Consumption (kWh) ÷ (30 × CUF × 24)
Real-World Example
A factory consumes 120,000 kWh per month.
Assume CUF = 16% for rooftop solar.
Solar capacity =
120,000 ÷ (30 × 0.16 × 24)
= 120,000 ÷ 115.2
= ~1,041 kW
Factory needs ~1,041 solar to meet this load.
Roof Area Determines Solar Capacity
Energy consumption alone doesn’t determine your system size. Roof area is often the biggest limiting factor. Most industrial roofs are filled with ducts, tanks, vents, or uneven structures that affect usable space.
As a general guideline, 1 kW of solar requires around 10 sq. metres of shadow-free space. This includes room for the panels, proper tilt, maintenance walkways, and safe access routes.
So, a 500 kW rooftop plant requires around 5,000 sq. metres of unobstructed area. Even small obstacles can disrupt the layout or reduce your maximum installation capacity.
For Ground Mount 1 MWp Solar capacity needs 3-4 Acres of land
The Importance of Shadow-Free Roof Space
Solar panels deliver their best performance when they receive uninterrupted sunlight. Industrial rooftops often have chimneys, HVAC units, parapet walls, or adjacent buildings that cast shadows. Even a short duration of shade on a panel can cause generation loss, create hotspots, and accelerate cell degradation.
Weather Conditions and Their Impact on Solar Output
Solar generation varies based on location. Regions like Rajasthan, Gujarat, Telangana, and Maharashtra enjoy high solar irradiation, ensuring stronger output. Coastal, cloudy, or high-humidity regions may experience lower generation due to atmospheric conditions.
Weather factors influence the Capacity Utilisation Factor (CUF) of your system, which directly affects annual energy yield. Understanding local weather ensures accurate generation forecasts and realistic ROI expectations.
Structural Load Capacity: Can your Roof Support Solar?
A solar installation adds weight to your rooftop structure. Panels, mounting structures, and wind loads together exert significant pressure. Your roof should ideally support 70–80 kg per sq. metre at each mounting point to ensure safe, long-term operation.
The Importance of Distance: Keep the Solar Plant close to your Load Centre
The location of the solar plant matters. When the distance between the solar installation and the consumption point increases, cable losses increase and cost of the plant also increases. This leads to:
- Reduced system efficienc
- Heat buildup
- Faster equipment degradation
Keeping the solar plant close to your consumption area, especially on the rooftop ensures stable voltage levels and optimal performance.
Water Requirement for Cleaning Solar Panels
For maximum efficiency, solar panels must remain clean. In industrial zones, dust accumulation is usually higher than residential areas.
Cleaning requirement guideline:
1 kWp of solar requires 35–40 litres of water per month
Water quality matters too its TDS should be below 500 ppm to prevent mineral deposits.
Orientation and Tilt of Solar Panels
The direction and angle of panel installation significantly affect solar absorption. In India, south-facing panels with an optimal tilt aligned to the site’s latitude offer the best generation. Adjustable mounts can further optimise performance by adapting tilt for seasonal changes.
An accurate orientation and tilt strategy improves daily output, enhances reliability, and boosts total annual generation. Though it may appear simple, this engineering calibration plays a major role in plant efficiency.
How FPEL Determines the Right Solar Capacity for your Factory
Solar sizing is not guesswork, it’s a data-driven, engineering-led process. At Fourth Partner Energy, we follow a structured approach to deliver accurate and reliable solar solutions.
Consumption Analysis
FPEL begins the process with a thorough analysis of your factory’s energy usage by studying 12 months of electricity bills. This allows our team to understand how power is consumed on a daily and monthly basis, how different operational shifts impact load patterns, and how consumption fluctuates across seasons. We also examine peak hours to identify when your factory requires the most energy and assess the proportion of daytime versus nighttime usage. This detailed consumption analysis helps us determine how much of your electricity demand can be effectively met through solar power during sunlight hours without leading to wastage or export loss.
Detailed Site Survey
Once the energy profile is clear, our engineers conduct an on-ground site survey to evaluate the physical and structural feasibility of installing solar at your facility. During this assessment, we examine the available rooftop area and verify whether it is sufficient and optimally placed for solar installation. We also study the movement of shadows across the roof to ensure long-term, unobstructed sunlight exposure. The survey includes checking the structural stability of the roof, analysing cable routing possibilities, and reviewing all safety and compliance requirements. We also inspect termination points to identify the most efficient way to connect the solar plant to your internal power system. This comprehensive survey ensures that the proposed design is practical, safe, and aligned with your operational needs.
As part of our ESG-first approach, FPEL ensures the plant is installed with all required safety and sustainability measures, including dedicated walkways for safe movement, lifeline systems for maintenance crews, mesh protection over skylights, and railings on rooftop edges. These features safeguard both your infrastructure and your workforce.
Optimised Plant Design
With a clear understanding of your energy consumption and on-site feasibility, FPEL proceeds to design a customised solar solution for your factory. Our engineering team recommends the ideal system capacity best suited to your load profile and roof conditions, while also estimating the annual energy generation you can expect. We evaluate the financial benefits, including projected savings and the return on investment, to ensure the project aligns with your business goals. The final design includes a detailed layout of panel placement along with shading analysis to maximise energy output. This approach results in a solar system that is efficient, financially attractive, and tailored to deliver long-term performance.
Regulatory Compliance & State-Specific Expertise
Solar regulations vary across states—net metering rules, system size limits, transformer loading, technical standards, and DISCOM approvals can all influence plant sizing. FPEL’s regulatory experts ensure your system is sized in full compliance with state policies, avoiding project delays or approval issues. This ensures the design is not just technically sound but also legally permissible and future ready.
Revent Precision Engineering Ltd – 1 MWp
Rooftop System in Pune
HUL – 2.3 MWp Ground Mount Solar System in Assam
Rooftop Solar Plant for HUL
Open Access as an Alternative for Larger Power Needs
Sometimes, the rooftop area simply isn’t enough to meet a factory’s energy demand. In such cases, businesses choose large-scale offsite renewable options through Open Access.
Enterprises can procure clean energy from:
Open Access allows factories to source power directly from large-scale renewable plants, delivering high-volume energy at competitive tariffs with zero upfront investment. This model is ideal for energy-intensive industries targeting deep decarbonisation and cost reduction.
FPEL is one of India’s leading Open Access renewable providers, powering C&I clients with reliable, utility-scale green energy solutions across multiple states.
Solar Sizing Is a Science - Let Experts Do It Right
Determining how much solar power your factory needs require a careful balance of energy data, engineering design, roof feasibility, and site-specific conditions. With the right approach, solar energy can significantly reduce electricity bills, improve operational stability, and strengthen your sustainability journey.
FPEL brings deep expertise in industrial solar solutions—from rooftop installations to ground-mounted and Open Access projects—ensuring every plant delivers maximum efficiency and long-term value.
FAQs
Can I still benefit from solar energy in areas with less sunlight?
Yes. Even regions with lower sunlight can benefit from solar power. While the energy output may be slightly lower, system sizing, panel type, and tilt angle can be adjusted to compensate. Advanced technologies like high-efficiency mono PERC panels and bifacial modules help maximise generation even in moderate sunlight conditions.
Is it possible to store excess solar energy for later use?
Yes. Solar energy can be stored using battery storage systems These systems store excess energy generated during peak sunlight hours, enabling factories to use it during the night, cloudy periods, or peak tariff hours. Storage is particularly useful for achieving partial or full energy independence.
What are the financial models available for installing solar?
There are two main financial models:
– CAPEX Model:
You buy and own the solar system by paying upfront.
– OPEX (PPA) Model:
You pay nothing upfront. The developer installs and owns the system, and you pay only for the solar power you use.