Factory solar system: A practical guide to sizing, costs, and installation

Key Takeaways

A factory solar system should be designed around the plant’s electricity use and business priorities, not simply the available roof area.

• Start with production loads, operating hours and electricity bills.
• Check roof condition, shading and structural capacity before settling on a system size.
• Compare grid-connected solar and storage options against the factory’s actual operating needs.
• Assess costs using the same equipment, installation scope and lifecycle assumptions across quotes.
• Build the business case from your own energy data, then request a load-based site assessment.

What Is a Factory Solar System?

A factory solar system is a photovoltaic system designed to supply some or all of a factory’s electrical loads from solar panels. Its size and configuration depend on what the plant uses electricity for, when it operates and how much power it can use as it is generated. For a factory owner, the aim is to align the design with production and the cost of purchased electricity.

How factory solar differs from an office system

Factories often have a broader mix of loads than offices, including production equipment, ventilation, refrigeration and process support systems. Some loads run steadily, while others start and stop or operate only during particular shifts. Those patterns affect how much solar electricity the site can use directly. Start with the production schedule and the loads that matter most to output, rather than treating the roof as the design brief.

That is why production comes first in a factory assessment. The same amount of roof space can suit different systems depending on the plant’s demand profile and the electrical connection. ZenSolar focuses on commercial and C&I solar, with Fox ESS inverters and batteries available through its offer. Its Sigenergy inverter and battery options are handled through a quote and site assessment.

Grid-connected, battery-backed and hybrid options

A grid-connected system uses solar power while it is available and remains connected to the electricity supply. Adding battery storage can shift some solar energy for use at a different time. A hybrid design combines solar, storage and the grid, with the right arrangement depending on the factory’s operating plan and electrical requirements.

Do not assume that a battery is needed simply because the site is industrial. Compare the cost and expected use of stored energy with the value of using solar directly. For context, solar thermal is a separate technology from photovoltaic electricity: global solar hot-water thermal capacity was 560 GWth at the end of 2023, up 3% from 2022, according to Wikipedia: Solar water heating; the background is also available at Wikipedia: Solar water heating. That figure describes thermal systems, not factory PV output.

What Can a Factory Run on Solar?

A factory can use solar electricity for electrical loads that operate when the system is producing power, subject to the site’s design and electrical setup. It may serve production equipment, building services or both. The useful question is not whether a particular machine can run on solar in isolation, but how its demand fits with the power available and the rest of the plant’s loads.

Production machinery and equipment

Production machinery can draw substantial power, and its use may change sharply as processes start, pause or switch between stages. A load assessment should identify which equipment operates during sunny hours and how those machines affect total site demand. The design also needs to account for the factory’s electrical distribution and the requirements of its equipment.

Where machinery runs outside solar production hours, a grid-connected system may still offset other daytime loads. Storage may help shift energy, but its value depends on the load and operating pattern. Treat each production process as part of the overall load profile rather than promising that panels alone will supply every machine at every moment.

Lighting, offices and refrigeration

Lighting, office equipment, ventilation and refrigeration can provide a more consistent daytime demand alongside production. Mapping these building loads helps show how much solar power the site can use as it is generated. In a plant with variable production, these steady loads may still make a useful part of the overall picture.

Thermal solar collectors are another distinct topic when a factory has a suitable heating demand. The source describes transpired solar collector systems as reducing conventional heating load by between 10 and 50%, based on monitoring by Natural Resources Canada and NREL; see Wikipedia: Solar thermal collector and Wikipedia: Solar thermal collector. That finding concerns solar air heating, not photovoltaic electricity for machinery, so keep the two technologies separate when comparing options.

Peak demand and operating-time matching

A factory’s total energy use does not tell you when its highest demand occurs. Compare the site’s demand profile with solar production hours to understand whether solar can serve the load directly or whether storage and grid supply need to play a role. The charge structure on the bill also matters, so examine energy use and demand charges separately where they apply.

When you review the profile, look for periods when the plant’s demand is likely to match available solar power and periods when it will not. This makes the design discussion specific to operating hours instead of relying on an annual energy total alone. It also gives you a clearer basis for comparing panels alone with a system that includes storage.

How to Size the Right System

Sizing a factory solar system starts with measured electricity use and the schedule behind it. Roof area matters, but it cannot tell you how much of the system’s output the plant can use or whether the electrical design suits the site. A sound assessment brings together consumption, timing, roof conditions and the role you want storage to play.

Start with the electricity bill and operating schedule

Gather bills that show the factory’s energy use and charges, along with the operating schedule for each production area. If available, interval data can help reveal how demand changes through the day. Record any planned changes to shifts, equipment or production, because a design based only on current use may not fit the plant for long.

Use the information to distinguish regular daytime demand from loads that run at other times. A national tariff trend can provide context, but it cannot predict a factory’s own savings: the CSIR reported that the national average electricity tariff increased by an average of 10% per year from 2014 to 2024, compared with average inflation of 5.2% over that period. That historical figure is not a substitute for your tariff and consumption data.

Account for roof space, shading and structural conditions

A roof survey should establish usable area, shading, roof condition and whether the structure can support the proposed equipment. A roof that looks open from the ground may have obstructions, access needs or sections that are unsuitable for panels. Roof orientation matters too, with north-facing roof areas generally receiving the best sun in South Africa.

Use a short site checklist to make the assessment more complete:

• Record roof sections, obstructions and areas affected by shade.
• Note roof condition, material and any planned maintenance.
• Identify routes for cables and access for installation and servicing.
• Check where the electrical equipment can be located and connected.

These details help an engineer judge how much of the roof is genuinely usable and what work the design may require. They also make it easier to compare proposals on the same physical site conditions.

Choose between panels alone and solar with storage

Panels alone may suit a factory that can use a meaningful share of solar power during production hours. Storage adds another design choice: it can store energy for later use, but its role should be tied to a defined operating need and assessed against its additional cost. A battery should not be treated as an automatic part of every factory system.

Ask the designer to explain how the options relate to your load profile, grid connection and business continuity requirements. If the plant has a reason to value control over its own supply, include that in the assessment while keeping it distinct from the direct electricity cost calculation. The comparison should make the trade-offs clear, rather than assuming one configuration is best for every factory.

What Does a Factory Solar System Cost?

The cost of a factory solar system depends on the site and on what the proposed system includes. A useful quote shows the design assumptions, equipment and installation scope clearly enough for you to compare alternatives. There is no reliable factory-wide price to apply without those details.

The inputs that shape the quotation

System size, equipment selection, roof conditions, electrical work and storage all affect a quotation. So can the access and installation requirements of an operating industrial site. Ask which assumptions the design uses, including the load profile and the amount of solar electricity expected to be used on site.

For a business case, keep tax questions specific to the taxpayer and project. SARS states that individuals who pay Personal Income Tax and install new and unused PV panels can claim 25% of the panel cost, up to a maximum rebate of R15 000, against their tax liability; see SARS and SARS. That statement concerns individuals and should not be treated as a factory company’s tax allowance.

Compare quotes using the same system scope

A low headline figure is not enough to judge two proposals. Check whether each quote covers the same system capacity, storage, electrical work, roof work, monitoring and commissioning. If one proposal leaves out work that another includes, the prices are not directly comparable.

Ask each supplier to show what is included and what depends on site findings. ZenSolar offers commercial and C&I solar, with Fox ESS inverters and batteries as part of its offer. Make sure any proposal you compare identifies the equipment and scope rather than relying on a broad system label.

Plan for lifecycle and replacement costs

The purchase price is only one part of the decision. Consider how the system will be monitored and maintained, what warranty terms cover, and how component replacement could affect the factory’s costs over time. Those details matter for a long-lived asset that supports a working site.

Ask suppliers to set out warranty coverage and the process for handling a fault. A clear proposal should also make responsibilities for maintenance and monitoring understandable. Include those points in your financial comparison so that you are not weighing only the upfront cost against expected electricity savings.

How the Installation Process Works

A factory installation should move from site and load assessment to an engineered design, then installation and commissioning. Each stage needs to account for the fact that the building is an operating plant. Good preparation gives the factory team a chance to coordinate access, work areas and any electrical changes.

Site assessment and load analysis

The assessment brings together the electricity data, operating schedule, roof conditions and site constraints. The supplier or design team needs to understand how production loads behave and where the proposed system can connect. Be ready to explain which operations must continue during installation planning and what site access rules apply.

A load analysis should help you understand the proposed system’s relationship to actual demand. Review the assumptions and ask how the design treats shifts, changing production levels and loads that run outside solar hours. That discussion is more useful than choosing a system size from roof area alone.

Engineering design and equipment selection

The engineering design turns the site information into a proposed layout and electrical arrangement. It should account for the roof, shading, equipment location, connection requirements and the planned use of solar energy. Ask for technical documentation that explains the system scope and identifies the main equipment.

If storage is included, the design should make its intended role clear in relation to factory demand. If panels alone are proposed, ask how the expected solar production lines up with daytime use. These are practical questions about fit, not just component selection.

Installation, testing and commissioning

Before work starts, agree on access, site safety arrangements and how installation activity will be coordinated with production. The plan should account for areas where work could affect plant operations. Once installation is complete, testing and commissioning confirm that the system has been set up and connected as designed.

Ask what handover information you will receive, including operating guidance and details for monitoring or maintenance. Keep those records with the factory’s electrical and asset documents. That gives the people responsible for the site a clear reference after the installation team has finished.

What Should You Check Before Choosing a Supplier?

The supplier’s proposal should be clear enough for your technical and finance teams to review. Look for evidence that the design responds to industrial loads and site conditions, not just a generic package description. Good questions at this stage can expose gaps before they become assumptions in the final decision.

Verify industrial experience and technical documentation

Ask how the proposed design addresses the factory’s loads, roof and electrical connection. Request technical documents that describe the system layout, equipment and assumptions. The documentation should give your team enough information to understand what is being proposed and what remains to be confirmed.

Check that the supplier has understood the production schedule and site access needs. A proposal that does not explain its load assumptions may not reflect how the plant actually operates. Compare the design basis as well as the headline system size.

Check warranties, maintenance and monitoring

Review the warranty terms for each main component and ask how service requests are handled. Clarify what monitoring is included and who is responsible for maintaining the system. Those answers help you understand the ongoing work expected from the factory after commissioning.

Keep the comparison specific. Check whether the scope includes monitoring equipment, maintenance arrangements and the documentation needed to operate the system. Do not assume that two proposals offer the same level of support just because both include panels and an inverter.

Confirm safety, protection and compliance work

Ask how the proposal deals with electrical protection, safe isolation and the factory’s site safety requirements. The design should identify relevant work at the point of connection and explain what approvals or checks are needed for the site. Make sure responsibilities are clear between the supplier, installer and factory team.

Agree how installation activity will be coordinated around production and access rules. Ask who will provide commissioning records and the handover documents. Clear roles and records are part of a complete project scope, not minor details to settle after a purchase.

How to Build a Business Case

A factory solar business case should use the site’s own energy and operating data. It should separate the value of reduced purchased electricity from any value assigned to storage or business continuity. Then test the result against plausible changes in production and system performance rather than relying on a single optimistic scenario.

Calculate the value of reducing purchased electricity

Start with the factory’s bills, tariff structure and demand profile. Estimate how much solar electricity can be used on site, then compare the value of that energy with the full cost of the proposed system. The estimate should reflect the system scope in the quote and the plant’s actual operating pattern.

South African electricity tariff trends may help explain why businesses are reviewing energy costs, but the factory’s own tariff determines its economics. The CSIR’s reported national average increase provides context, while the site-specific calculation should use the figures on your bill. This keeps the business case grounded in the costs your business actually faces.

Test the value of demand and outage management

Consider whether storage or another part of the design has a defined role in managing demand or supporting business continuity. Describe that role in operational terms, then ask how it changes the system cost and expected use of electricity. Avoid assigning a financial value to a benefit unless you can explain how it applies to the plant.

If the factory has critical operations, identify what those are and what level of continuity the business needs. The design discussion can then test whether storage is relevant and what it would need to support. Keep that question distinct from the simpler calculation of electricity bought from the grid.

Compare the investment with realistic operating scenarios

Use more than one operating scenario if production, shifts or energy use may change. Compare the expected case with a lower-use case and a case that reflects planned growth, where those are relevant to the factory. Record the assumptions behind each one so that decision-makers can see what drives the result.

Include system and lifecycle costs in the comparison, not only the expected reduction in purchased electricity. A useful business case lets you change an assumption and see how the conclusion moves. That is more credible than presenting a single return figure without showing the inputs behind it.

What Should a Factory Owner Do Next?

The next step is to assemble the information that makes a site assessment useful. You do not need to choose equipment before the loads, roof and operating pattern have been reviewed. Start with what the factory already knows, then ask for a proposal based on those facts.

Gather electricity bills and operating information

Collect electricity bills, available interval data and a clear description of operating hours. Note major production equipment, refrigeration and other large loads, along with any planned changes to the plant. Include roof drawings or maintenance information if you have them, and flag access or safety requirements for the site.

This gives the assessment a practical starting point. It also helps you spot missing information early, before different suppliers make different assumptions about the factory. Keep the data together so that each proposal can be reviewed against the same baseline.

Request a load-based site assessment and quotation

Ask for a site assessment that considers the load profile, roof, electrical connection and proposed system scope. Request a quotation that explains the equipment and work included, along with the assumptions used in the design. ZenSolar serves commercial and C&I customers and presents solar as a decision about the plant’s costs and operating needs.

Conclusion

A factory solar system is most useful when it matches production demand, site conditions and the factory’s financial priorities. Start with the bills and operating schedule, check the roof and electrical requirements, then compare clearly scoped proposals and realistic business cases. That gives you a sound basis for deciding whether panels alone or solar with storage suits the plant.

Frequently Asked Questions

What is a factory solar system?

A factory solar system uses photovoltaic panels and associated electrical equipment to supply some or all of a factory’s electrical loads. Its design depends on energy use, operating hours and site conditions.

Can solar power run factory machinery?

Solar can supply machinery when the system and electrical connection are designed for the relevant loads. The assessment should consider when the machinery runs and how its demand fits with available solar power.

Does a factory solar system need batteries?

No. A battery is an option, not a requirement for every factory. Its role should be assessed against the site’s operating pattern, energy needs and the additional system cost.

How do you size solar for a factory?

Start with electricity bills, available demand data and the operating schedule. Then assess the roof, shading, structural conditions and the intended role of storage.

What affects the cost of factory solar?

System size, equipment, roof and electrical work, storage and installation conditions can all affect a quotation. Compare proposals only after checking that they include the same scope.

How long does factory solar installation take?

The timeline depends on site conditions, project scope, engineering and installation coordination. Ask the supplier for a project schedule based on the factory’s specific requirements.

What information should you prepare before requesting a proposal?

Gather bills, operating hours, major loads, available demand data and information about the roof and site access. When you are ready, book a Discovery Call with ZenSolar to discuss your factory’s numbers and next steps.