Does installation timing affect the cost and performance of commercial solar?
Installation timing affects 4 variables: installer lead times, STC rebate value, tax deduction timing, and initial system output. A business with flexibility over when it installs can optimise across all four. February to April and July to September are the two windows that balance installer availability, weather conditions, and financial year planning most effectively across Sydney, Brisbane, Melbourne, Perth, and Adelaide.
Why is the EOFY rush a problem for commercial solar installation?
The end of financial year (EOFY) period from April to June is the busiest installation window in Australia because the instant asset write-off and standard depreciation deductions both require the asset to be installed and ready for use before 30 June. Business owners, often prompted by accountants during tax planning conversations in March and April, rush to lock in purchases and get systems commissioned before the deadline.
The practical consequence: lead times that run 2 to 3 weeks in February stretch to 6 to 8 weeks or longer in May. Installer crews across NSW, Queensland, Victoria, and Western Australia book out weeks in advance. Businesses planning to install before 30 June should start the process in March, not June. Under the ATO’s instant asset write-off rules, the system must be first used or installed ready for use before the deadline, not just contracted or paid for.
How does installation timing affect the STC rebate value?
The Small-scale Renewable Energy Scheme deeming period reduces by one year on 1 January each year, which means a system installed in December generates more STCs and a larger rebate than the same system installed in February the following year. For a 13kW system, the difference between installing in December versus January is approximately $200 to $400 in STC value.
This is a secondary consideration for most businesses. The tax deduction timing and installer availability typically carry more financial weight than the marginal STC difference. Full details on current rebate values are on our solar rebates page.
What are the best and worst seasons to install commercial solar?
Autumn (March to May) and post-EOFY winter (July to September) offer the best combination of installer availability, stable weather, and competitive pricing.
Summer (December to February) delivers immediate high output because days are long and irradiance peaks across all Australian capital cities. It is also a quieter booking period for commercial installers, which means shorter lead times and competitive quotes. The trade-off in northern states like Queensland is occasional installation delays from wet-season storms.
Autumn provides stable, mild weather across most of Australia. Installation crews work efficiently, and businesses booking in March or April are far enough from 30 June to secure a slot without the EOFY premium on lead times.
Winter (June to August) is the post-EOFY window. Installer availability opens up significantly in July and August. Quotes tend to be competitive, bookings are prompt, and weather delays are rare in most states. System output is lower in winter months, but this has no impact on the long-term financial case.
Spring (September to November) sees demand build as businesses begin EOFY planning for the following financial year. Booking in spring means the system generates savings through summer and is operating well before the next 30 June deadline.
How should a business match solar installation to its tax calendar?
Install in a financial year where your business has strong taxable profit, so the depreciation deduction or instant asset write-off offsets the most tax.
- Strong profit year: install before 30 June to claim the deduction in the current financial year
- Loss year or reduced profit: consider delaying to the next financial year when taxable income is higher
- Planning a system above 10kW: start the process at least 3 months before your target install date
- Adding battery storage: battery lead times can run longer than panels, so factor in additional weeks
A 6.6kW solar system typically takes 4 to 8 weeks from quote to commission. A 13kW system or larger takes 6 to 12 weeks, and systems above 30kW may require 10 to 16 weeks including network approvals.
What grid connection approvals can delay a commercial solar installation?
Commercial systems above 10kW typically require a connection application to the local Distribution Network Service Provider (DNSP) before installation, and approval takes 4 to 8 weeks or longer. DNSPs include Ausgrid and Endeavour Energy in NSW, Energex in Queensland, CitiPower and Powercor in Victoria, and Western Power in WA.
Businesses targeting a 30 June commission date cannot leave the network application until June. The application, design approval, installation, inspection, and meter reconfiguration all need to complete within the financial year. Starting the quote process in February or March provides enough buffer for each step.
What is the best time to install commercial solar in Australia?
February to April for businesses with an EOFY tax deadline, or July to September for those without time pressure, delivers the best balance of pricing, availability, and weather. There is no universally wrong time, but planning around the EOFY rush saves weeks of waiting and avoids the risk of missing the 30 June deadline.
To start the process, speak with the Solar Galaxy team for a free commercial solar assessment and installation timeline for your site.
This article is general information only and does not constitute financial or tax advice. Consult a registered tax agent for advice specific to your business.
