Green tariffs, REGO backed supply, on site generation and PPAs sit on a spectrum of cost, complexity and credibility. Here is how they differ.
The phrase renewable energy covers arrangements that vary enormously in cost and in how defensible they are when reported. Knowing where each sits on that spectrum prevents a business from paying for a claim it cannot substantiate.
At the simplest end, a green tariff matches your consumption with renewable certificates purchased by the supplier. It is inexpensive and easy, but the certificates may be bought separately from the electricity itself, which limits how strongly the claim can be made.
REGO backed supply contracts strengthen the position by tying certificates to the electricity supplied. This is the standard route for most businesses that want a credible renewable claim without complexity.
On site generation, typically rooftop solar, delivers the strongest claim because you consume what you generate. It requires either capital or a long term on site power purchase agreement, and it needs a roof and a load profile that match generation.
Corporate power purchase agreements sit at the top end. They connect you directly to a named generator over a long term, deliver traceable attributes and can stabilise price for a decade or more. They also involve genuine contractual risk and are only appropriate above a certain scale.
Choose based on what you need to prove, what you can commit to and how much consumption you actually have.