Installing solar panels for business can reduce grid electricity consumption, improve energy cost control and support corporate sustainability objectives. However, getting good results from commercial solar involves more than installing as many panels as the available roof can accommodate.
The system needs to match the business's electricity load.
A warehouse operating mainly during daylight hours, for example, has a very different load profile from a manufacturing facility running around the clock. Likewise, an office building may experience strong weekday demand but relatively little weekend consumption.
Therefore, the right commercial solar capacity depends on how much electricity the business consumes, when it consumes it and how those requirements may change.
Solar panels generate electricity according to sunlight availability. Businesses, meanwhile, consume electricity according to their operating schedules, equipment and production requirements.
The greatest opportunity generally occurs when these two patterns overlap.
If a solar system produces electricity while the site needs power, the business can consume that solar generation directly and reduce electricity purchased from the grid. This is known as solar self-consumption.
However, if generation exceeds the site's immediate requirements, surplus electricity may be exported to the grid. Exported electricity can still have value, but the financial outcome may differ substantially from avoiding the purchase of grid electricity.
Consequently, commercial solar sizing should start with the load rather than simply asking, "How much solar can fit on the roof?"
A load profile shows how electricity consumption changes throughout the day.
For example, consider two businesses that each consume 500,000 kWh annually. One operates primarily between 8 am and 5 pm, while the other has relatively constant 24-hour demand.
Although their annual electricity consumption is identical, their ideal solar systems may differ because their daytime demand patterns differ.
A detailed assessment should therefore examine:
| Load factor | Why it matters |
| Annual electricity consumption | Establishes overall energy requirements |
| Daytime consumption | Indicates potential solar self-consumption |
| Peak demand | Shows periods of highest electricity requirement |
| Weekend demand | Helps determine whether weekend solar generation can be used |
| Seasonal demand | Identifies changes between summer and winter |
| Operating hours | Shows how closely electricity demand aligns with solar production |
| Future requirements | Helps prevent a new system becoming undersized too quickly |
Interval meter data is particularly valuable because it reveals consumption across individual periods rather than simply providing monthly totals.
Commercial solar sizing requires several steps. Although preliminary estimates can help establish project feasibility, detailed modelling should use site-specific electricity and solar-generation data.
Start by reviewing at least 12 months of electricity data where possible.
Monthly bills provide useful information about total consumption and costs. However, interval meter data offers considerably more detail because it shows when the site uses electricity.
Look for recurring patterns. For instance, does demand rise sharply when production begins? Does consumption fall substantially on weekends? Does air conditioning create a summer peak?
These patterns determine how effectively solar generation can offset grid consumption.
Annual electricity use alone does not determine the ideal solar capacity.
Instead, businesses should pay particular attention to electricity consumed during solar-generation hours. A site with consistently high daytime demand may be able to accommodate a larger solar installation while maintaining strong self-consumption.
Consider a simplified example.
| Business | Annual usage | Daytime load | Solar opportunity |
| Office | 300,000 kWh | High on weekdays | Strong |
| Warehouse | 300,000 kWh | Moderate | Moderate to strong |
| Night operation | 300,000 kWh | Low | More limited without storage |
| Manufacturing plant | 1,500,000 kWh | High and consistent | Potentially substantial |
These examples illustrate why capacity should reflect operating patterns rather than annual consumption alone.
Next, estimate how much electricity the proposed system could generate throughout the year.
Generation depends on several factors, including location, panel orientation, tilt, shading, equipment efficiency and system losses. Roof geometry can also affect how much usable capacity a commercial property has.
Importantly, annual generation estimates are only part of the calculation. Businesses should compare expected solar output with electricity demand across the same periods.
That comparison provides an estimate of how much solar power will be consumed onsite and how much may be exported.
A larger solar system does not automatically produce a better financial result.
Suppose a business requires 300 kW during the middle of a typical working day. Installing enough solar to regularly produce substantially more than that demand could create significant exports unless the site has battery storage or another use for the surplus.
The business should therefore compare the value of self-consumed and exported electricity.
Oversizing isn't necessarily a mistake. In some circumstances, additional capacity can support broader business objectives.
For example, the company may plan to introduce electric vehicles, electrify heating, expand manufacturing or add another shift. Battery storage may also create opportunities to capture surplus generation.
Therefore, system design should consider the expected operating environment over the investment horizon, not merely today's consumption.
Being too conservative can also reduce the value of solar panels for business.
If a site has high, predictable daytime demand and suitable roof space, installing a small system may leave a large amount of economically useful solar potential untapped.
Furthermore, businesses expecting future growth should consider how electricity requirements could change. New machinery, electric vehicle charging, additional refrigeration or building expansion can all increase demand.
However, anticipated growth should be based on realistic business plans rather than optimistic assumptions.
Electricity demand and solar generation both change throughout the year.
Retail sites may experience stronger electricity requirements during busy trading periods. Offices can experience increased cooling loads during summer, while industrial sites may have production cycles that create significant seasonal variations.
Solar output also changes with weather conditions and daylight hours.
Therefore, sizing a system around a single month's electricity bill can produce misleading results. Using at least a full year of consumption information provides a stronger basis for assessing seasonal interactions between demand and solar generation.
Not necessarily.
Trying to generate annual solar electricity equivalent to 100 per cent of annual consumption can sound appealing. However, annual totals don't show whether electricity generation and consumption occur simultaneously.
A business might consume large quantities of electricity at night while producing surplus solar power during the afternoon. Although annual generation and consumption could appear balanced on paper, the site would still need grid electricity after sunset.
Instead, businesses should focus on the relationship between generation and consumption throughout the day.
Battery storage can change the equation because it allows a business to store some excess solar generation for later use.
For example, surplus afternoon generation could potentially support evening operations instead of being exported immediately.
This may make a larger solar system practical for certain businesses.
However, batteries introduce additional capital costs, operating considerations and degradation over time. Therefore, the solar and battery system should be modelled together rather than automatically adding storage to an existing solar proposal.
Battery storage can be worth investigating when a business has substantial electricity demand outside solar-generation periods, frequent surplus solar generation or opportunities to manage peak grid demand.
Nevertheless, the financial case remains site-specific. Businesses should compare the additional savings created by storage with the total cost and expected life of the battery.
Commercial buildings often have substantial roof areas, making it tempting to maximise installed solar capacity.
However, available roof space only tells you what can be installed. It doesn't determine what should be installed.
The design must also account for shading, roof condition, structural capacity, fire access, existing equipment and potential future building changes.
Therefore, roof capacity should form part of the technical assessment after the business understands its electricity load.
System capacity should ultimately support the project's financial and operational objectives.
Businesses should assess:
Solar may also form part of a wider business energy strategy. Energy Action's existing guidance, for example, considers onsite solar, solar PPAs and other renewable energy arrangements as potential components of commercial energy procurement.
Sizing solar panels for business effectively starts with understanding the electricity load.
Rather than selecting a system solely according to available roof space or annual consumption, businesses should analyse interval data, daytime demand, operating hours, seasonal patterns and realistic future requirements. They can then model solar production against those consumption patterns to identify an appropriate system size.
A well-sized system can increase self-consumption, reduce reliance on grid electricity and strengthen the financial case for commercial solar.
Energy Action can help Australian organisations understand their energy consumption and assess solar as part of a broader energy strategy. By combining energy data, procurement expertise and commercial analysis, Energy Action can help businesses make more informed energy decisions and identify opportunities to manage costs and sustainability objectives.
Visit Energy Action to explore business energy solutions and determine how solar could fit into your organisation's energy strategy.
Start with historical electricity consumption, preferably including interval meter data. Analyse how much electricity the business consumes during daylight hours and compare this load with expected solar generation throughout the day and year. A commercial solar assessment should also account for roof conditions, shading, electricity tariffs, exports and future demand.
Yes. A system can be economically oversized when it regularly generates considerably more electricity than the site can consume and the surplus has relatively limited value. However, additional capacity may still make sense when future expansion, electrification, batteries or other planned loads can use the extra generation.
Not automatically. Matching annual solar production to annual electricity consumption doesn't guarantee that the business can use all of that generation onsite because solar production and electricity demand occur at different times. Businesses should instead examine how closely solar generation aligns with their actual load profile.
No. Businesses with substantial daytime electricity consumption may already be able to consume a large proportion of solar generation directly. However, batteries may be worth assessing where significant solar generation would otherwise be exported or where stored electricity could support evening demand or demand-management objectives.
Ideally, businesses should gather at least 12 months of electricity bills and interval meter data, along with operating schedules and information about planned changes to the site. Roof condition, available area, shading, electrical infrastructure and future equipment requirements should also be assessed. Combining these inputs creates a much stronger basis for sizing solar panels for business than relying on annual electricity consumption alone.
