100kW Commercial Solar System: A Guide for Australian Businesses

Budget Petrol in Goulburn planned to install EV chargers, but the site's grid supply presented a challenge. The additional charger demand could have increased tariff costs and affected charger performance.

After an onsite assessment and analysis of the site's energy data, Quality Energy recommended supplementing the grid supply with rooftop solar. The team designed and installed a 99.9kW solar system with a special-order FIMER PVS-100 string inverter compatible with the DC EV chargers.

The 99.9kW capacity kept the project safely within the SRES limit that applied when the system was designed. The project modelling estimated:

• 25-year financial benefit: $491,151
• Estimated payback period: 5.8 years
• Estimated emissions avoided: 145.5 tonnes of CO2 annually
• Solar output warranty: 30 years

These figures are project-specific forecasts rather than standard results for every 100kW system. The business's load profile, electricity tariff, site conditions, system cost and export arrangements all influenced the outcome.



Quality Energy looks beyond the solar array when assessing a commercial site. As a manufacturer and supplier of power quality equipment, we can examine solar alongside your existing power quality, including any demand charges, or proposed impact of renewable energy to power quality. 

The Small-scale Renewable Energy Scheme creates STCs for eligible solar installations, which are exchanged for an upfront reduction in the purchase price. 

For systems installed in 2026, the standard solar STC calculation uses a five-year deeming period. The ordinary deeming period then falls to four years in 2027, three in 2028, two in 2029 and one in 2030. 



On 5 August 2026, the Australian Government announced plans to expand the SRES to mid-scale solar PV. The change is intended to make systems above 100kW and no more than 1MW eligible to create STCs from 1 October 2026, estimated to reduce upfront costs by around 20%. Our post on the SRES expansion changes explains this further.

A 100kW system requires around 500 to 650 square metres of usable roof area. The amount depends on the number and dimensions of the panels, their orientation, the mounting system and the clearances required around roof edges, access routes, vents and other equipment.

Usable roof area matters more than total roof area. Quality Energy assesses:

• structural condition and load capacity
• roof pitch, orientation and shading
• skylights, vents, HVAC equipment and other obstructions
• access and installation requirements
• fire and maintenance pathways
• heritage, planning and council requirements where applicable



Some sites can support a larger system than first expected, while others need a smaller array or additional engineering work. A roof plan and structural assessment provide a more reliable answer than estimating capacity from building dimensions alone.

A 100kW solar system can be paired with commercial battery storage during the initial installation or added later. 

A well-designed battery can extend the value of a 100kW solar system by storing excess daytime generation for use later. It can help reduce peak demand, increase solar self-consumption and support selected equipment during a power outage.

Quality Energy uses interval data, solar production, demand peaks and operating hours to recommend a battery capacity suited to the business. The battery, inverter, switchboard and backup circuits can then be configured around priorities such as evening energy use, essential equipment, EV charging and future electrical demand.

Solar used onsite reduces the amount of electricity bought from the grid during daylight hours. Savings depend on the site's tariff and the proportion of generation consumed by the business.

Onsite generation can reduce exposure to future retail electricity price movements. It does not eliminate the bill because network charges, demand charges, fixed fees and electricity used outside solar-production hours may remain.

Eligible systems rated at no more than 100kW may receive an upfront STC discount. From the intended October 1 commencement of the 2026 expansion, eligible systems above 100kW and up to 1MW may also qualify.

Solar generates electricity without direct operational greenhouse gas emissions. Businesses can use verified production data to support internal energy and emissions reporting, subject to the accounting method they apply and any treatment of renewable energy certificates.

Solar can form part of a wider energy plan that includes EV charging, equipment electrification, battery storage and power quality management. These loads should be modelled together so the electrical infrastructure and generation capacity work as intended.

Good performance starts with a design based on the site's interval electricity data. Once installed, the system should be monitored so faults, inverter outages and unexpected drops in production can be investigated promptly.

Cleaning requirements depend on rainfall, dust, bird activity, roof pitch and the site's operating environment. Panels should be inspected and cleaned when condition or performance data indicates it is needed, following manufacturer instructions and safe-access procedures.



Businesses can also improve self-consumption by scheduling suitable loads during solar-production hours. The opportunity depends on operating requirements and should not interfere with production, safety or equipment performance.

Choosing a New Energy Tech Consumer Code (NETCC) Approved Seller gives you added confidence when investing in commercial solar, battery storage or EV charging. Quality Energy has demonstrated that its sales practices, quotes, contracts, installation processes, warranty support and complaints procedures meet the NETCC’s consumer protection standards. 

For your business, this means clearer information about costs and expected performance, fair contract terms and support after the system is installed. On a commercial solar project involving a substantial capital investment, these standards make it easier to compare proposals and understand who is responsible for the design, installation, warranties and any issues that may arise.

A commercial solar project follows these stages:



1. Energy and site assessment: We review interval data, electricity bills, tariffs, operating patterns, switchboards, roof conditions and future energy plans.
2. Preliminary design: We model a suitable system capacity, expected production, self-consumption, energy savings and emissions reduction.
3. Network application: The proposed system is submitted for the required distributor assessment and connection approval.
4. Detailed design and proposal: The system design, equipment, project scope, costs, certificate assumptions and financing options are confirmed.
5. Planning and engineering: Structural, electrical, access and planning requirements are addressed before installation.
6. Installation: SAA-accredited installers and licensed electricians complete the approved work.
7. Commissioning and metering: The system is tested, commissioned and connected with the required monitoring and metering arrangements.
8. Performance review: Monitoring helps confirm production and identify performance issues after handover.
   

A 100kW system may suit a business with substantial daytime electricity use, suitable roof space and a grid connection that can accommodate the installation. It should not be treated as a standard package for every commercial property.

For some sites, 60kW may produce a better return. Others may be able to use 250kW, 500kW or close to 1MW, particularly if the business is adding EV charging, electrical equipment or battery storage. The proposed SRES expansion may improve the upfront cost of these larger projects, but the system still needs to be designed around the site's demand and connection limits.

Get a commercial solar feasibility study with Quality Energy before committing to a system size. We can assess your interval data, tariffs, roof, network requirements and future loads, then prepare a business case based on the capacity your operation can use.