Commercial solar: why 100 kW changes everything

If you are pricing solar for a business, there is a single number that shapes the entire financial model: 100 kW. Below it you are in one scheme. At or above it, you are in a completely different one.

Under 100 kW — money off the invoice

Systems below 100 kW create Small-scale Technology Certificates. These are calculated on deemed future generation — system size, location and the years remaining before the scheme ends in 2030 — and your installer deducts their value from your price on day one.

The appeal is obvious: lower capital outlay, no ongoing administration, nothing to manage. The catch is that the entitlement shrinks every January as the deeming period shortens.

At or above 100 kW — revenue over time

Cross the threshold and your system creates Large-scale Generation Certificates instead: one per megawatt-hour actually generated, every year it runs. There is no upfront discount. You fund the full system, then earn certificates on real output.

That is genuine ongoing revenue, but it demands more capital upfront and brings obligations — registration, compliant metering and someone to handle the trading.

The awkward middle

A 99 kW system captures the upfront discount. A 110 kW system generates more energy but forfeits it. Between those two points sits a real decision, and it depends on your cost of capital, your appetite for administration, and how much roof you have.

Some businesses stage it: install just under the threshold, capture the discount, then expand later. Whether that works depends on your roof, your switchboard and your network agreement.

The incentive most businesses forget

The instant asset write-off is not an energy scheme, but for eligible businesses it can be the single largest lever on the after-tax cost of a system, and it stacks with certificate discounts. Thresholds change between years, so it is a question for your accountant rather than your installer.

What to insist on

Ask for the certificate discount as a separate line item. Ask for the design to be based on interval data rather than your bill total. And ask to see the model on both sides of the threshold before anyone recommends a size.

Our commercial rebates page sets out both schemes side by side.