Key takeaways
- On-grid solar has no batteries and switches off during a grid outage for safety.
- Size the system from your daytime consumption, sanctioned load and usable roof area.
- Plants with DG sets need controls that stop solar feeding back into the generator.
- Payback depends on your tariff, generation and installed cost; model it with your own bills.
For manufacturers in Faridabad and across Haryana, electricity is one of the largest controllable operating costs. Rooftop on-grid solar is one of the few investments that reduces it directly, and factories are unusually well suited to it. This guide covers what to consider before you commission a system.
Why factories are a strong fit for solar
- Daytime demand: most production runs while the sun is up, so solar power is used on site instead of being exported.
- Large roofs: industrial sheds and flat roofs offer space that is otherwise unused.
- Commercial and industrial tariffs: every unit generated displaces a relatively expensive unit from the grid.
- Predictable loads: consumption patterns are easier to model than in many commercial buildings.
On-grid, off-grid and hybrid: which one?
| Type | Batteries | During a grid outage | Best suited to |
|---|---|---|---|
| On-grid (grid-tied) | No | Shuts down automatically for safety | Sites with reliable grid supply focused on cutting bills |
| Off-grid | Yes | Keeps running from batteries | Remote sites with no grid connection |
| Hybrid | Yes | Supplies backed-up loads | Sites that need backup for critical loads |
On-grid systems are the most common choice for factories because they cost the least per unit generated. They switch off when the grid fails, a protection known as anti-islanding, so that no power is fed into lines utility staff may be working on.
If your plant runs diesel generators
This is the most frequently overlooked design point for factories. When the grid fails and a DG set starts, a solar inverter must not push power back into the generator, which can damage it. Plants that run DG sets need a DG synchronisation or zero-export controller that limits solar output to below the site load while the generator runs. Plan this into the design from the start.
How to size a factory solar system
1. Start with consumption
Gather at least twelve months of electricity bills and, ideally, load profile data from your meter. What matters is how much energy you consume during daylight hours on working days, and how that changes through the week and the year.
2. Check your sanctioned load and regulations
Distribution companies and the state regulator set rules on how much rooftop capacity can be connected relative to your sanctioned load or contract demand, and on how exported energy is treated. These rules change, so confirm the current position with your discom or your installer before finalising capacity. In south Haryana, including Faridabad and Gurugram, the distribution company is DHBVN.
3. Measure usable roof area
Only shade-free roof counts. Subtract areas shaded by parapets, water tanks, stacks and neighbouring buildings, and leave walkways for cleaning and maintenance. Modern modules generally need somewhere in the region of 80 to 100 square feet of usable roof per kWp, depending on module efficiency, layout and spacing.
4. Match capacity to use
The most economical system is usually one whose generation is largely consumed on site. Oversizing beyond daytime demand can reduce returns if exported units are credited at a lower value than the units they replace.
How much will it generate?
Well-installed rooftop systems in north India typically generate, on an annual average, roughly 3.5 to 4.5 units (kWh) per day for each kWp installed. Actual output depends on orientation, tilt, shading, module and inverter quality, and cleanliness.
Output varies through the year. Winter fog and smog, and cloudy monsoon days, reduce generation, while clear pre-monsoon months are strong. Dust is a particular factor in NCR: soiled modules can lose a noticeable share of their output, so a practical cleaning schedule is part of the design, not an afterthought.
Net metering and approvals
Under net metering, a bi-directional meter records both the energy you import from the grid and the energy your system exports, and you are billed for the net. Gross metering and other arrangements treat exported energy differently. Which schemes are available, and how exports are valued, is set by state regulations and discom procedures.
The typical sequence involves an application to the discom, technical feasibility review, installation, inspection and meter replacement before the system is formally connected. Larger installations may also require electrical safety inspection. Your installer should manage this process and keep you informed of each stage.
Roof and structural checks
- RCC roofs: structures are ballasted or anchored; waterproofing must be protected at every fixing.
- Metal sheet roofs: modules are mounted on rails clamped to the sheet profile; check the age and condition of sheets and purlins first, because replacing a roof under a solar array is expensive.
- Wind loads: mounting structures must be designed for local wind speeds.
- Access: safe access and walkways for cleaning and inspection.
Electrical design essentials
- String design matched to inverter input limits
- DC and AC cable sizing to keep losses low
- Protection devices, isolators and surge protection on both DC and AC sides
- Earthing of modules and structures, and lightning protection where required
- Inverter location with ventilation and protection from direct sun and dust
- Monitoring that shows generation by inverter so faults are spotted quickly
Solar connects into your main distribution system, so it should be designed alongside it. Our guide to industrial LT panels and earthing covers the electrical side of a factory in more detail.
Payback and financial benefits
Simple payback is the installed cost divided by the annual saving. For commercial and industrial rooftop projects in India, paybacks of a few years are commonly reported, but the figure for your plant depends on your tariff, your share of self-consumption, generation, installed cost and maintenance. Model it using your own bills rather than a generic figure.
Businesses may also have tax benefits, such as depreciation on the solar asset, that improve returns. Discuss these with your chartered accountant. Note that residential subsidy schemes are generally not available for factories and commercial premises.
Maintenance and monitoring
- Regular module cleaning, more frequent in dry, dusty months
- Monitoring of daily generation against expected output
- Periodic checks of connections, fuses, earthing and structure fixings
- Inverter fault logs reviewed and acted on promptly
- Thermal imaging of modules and connections to catch hot spots
1 Worldcrafts designs and installs on-grid rooftop solar systems for factories and commercial buildings, together with the electrical work to integrate them safely. Send us twelve months of bills and a roof plan for an assessment.
Frequently asked questions
No. An on-grid system shuts down automatically when the grid fails, so no power is fed into lines that may be under repair. If you need solar to support loads during outages, you need a hybrid system with batteries or a design that works with your DG set through a synchronisation controller.
As a rough guide, modern modules need somewhere in the region of 80 to 100 square feet of shade-free roof per kWp installed, including spacing and walkways. A site survey that accounts for shading, obstructions and roof condition gives the actual usable capacity.
Yes. Modules are mounted on rails clamped to the roof sheet profile, which avoids drilling where possible. The condition and remaining life of the sheets and purlins should be checked first, because removing and refitting an array to replace the roof later is costly.
It depends on local dust levels and the season. In dusty NCR conditions, cleaning is often needed far more frequently than in cleaner locations. Comparing monitored generation with expected output is the best way to set a cleaning interval that pays for itself.
Planning a project like this?
Send us your drawings or scope. Our engineers will review the requirement and come back with an itemised proposal.
