Time-matched Scope 2 explained

Why annual averages are costing Australian companies credibility

The problem with annual averages

Grid carbon intensity changes dramatically throughout the day. On a sunny afternoon in South Australia, it might drop below 0.1 tCO₂/MWh as solar floods the grid. By 7pm, with gas peakers ramping to meet evening demand, it can exceed 0.6 tCO₂/MWh. The annual average smooths all of this away into a single number.

If your operations consume electricity primarily during high-renewable periods, your actual emissions are materially lower than the annual average suggests. If you run overnight on coal-dominated baseload, they're higher. The annual average tells you neither of these things.

Under the Australian Sustainability Reporting Standards (ASRS), this is increasingly untenable. Investors and auditors expect methodology that reflects actual operating conditions — not a number that obscures them.

What time-matched Scope 2 does differently

Time-matched Scope 2 matches each consumption interval to the actual grid carbon intensity at that point in time. Instead of one annual number, you're working with 17,520 half-hour intervals per year — each one reflecting the real generation mix on the grid when your electricity was consumed.

The GHG Protocol supports this approach as a market-based method. The ASRS requires sufficient methodology disclosure to demonstrate that reported figures are robust and defensible. Time-matched calculations meet both requirements.

What the difference looks like in practice

The gap between annual-average and time-matched Scope 2 varies significantly depending on when and where you consume:

• Daytime manufacturer in NSW: time-matched emissions were 28% below the location-based figure — reflecting high midday solar penetration during operating hours.
• Overnight cold storage in VIC: time-matched emissions were 19% above the location-based figure — overnight consumption coincides with coal-heavy baseload generation.

For a company consuming 5,000 MWh per year, a 25% difference translates to hundreds of tonnes of CO₂e. That's material for disclosure, and it changes the business case for load-shifting, on-site generation, and power purchase agreements.

How to calculate time-matched Scope 2

You need two data sets: interval meter data from your retailer or network provider, and grid carbon intensity per interval for the region where you consume.

The formula is straightforward. For each interval, multiply your consumption in MWh by the grid carbon intensity in tCO₂/MWh at that interval. Sum all intervals across the reporting period. The result is your time-matched market-based Scope 2 figure.

gridIQ automates the entire process. Upload a CSV of your interval meter data, select your NEM region, and get both location-based and time-matched market-based calculations side by side. Export as PDF for your sustainability report.

Getting started

Every gridIQ account includes a 14-day Professional trial with full access to the Scope 2 emissions tracker. After the trial, the Scope 2 tracker is available on Team ($349/month) and Professional ($749/month) plans.

Try our free Scope 2 emissions calculator for a quick estimate, or create your account for full interval-level time-matched Scope 2 tracking.