Why annual averages are costing Australian companies credibility
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 when the grid carries more coal-fired generation, they're higher. The annual average tells you neither of these things.
Under Australia's mandatory climate reporting from 2026, this is increasingly untenable. The Australian Sustainability Reporting Standards (ASRS) require methodology that reflects actual operating conditions, not a number that obscures them.
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.
This is a more granular version of the location-based method. It still uses the grid-average carbon intensity for your region, just resolved to each half-hour rather than smoothed into a single annual figure. ASRS expects methodology that reflects actual operating conditions, and a time-matched location-based figure does exactly that.
A common mix-up is to call a time-matched figure “market-based”. It is not. Under the GHG Protocol the market-based method reflects the electricity you have contracted for, and it requires instruments: retired energy attribute certificates (large-scale generation certificates, GreenPower or REGO), or the published intensity of a generator you hold a power purchase agreement with. Without any of those, your market-based figure is unsubstantiated and simply equals your location-based figure.
gridIQ reports both methods. The location-based figure can be time-matched to half-hourly grid intensity for accuracy, and the market-based figure is built from the instruments you actually hold, so an auditor can see exactly what substantiates each number.
The gap between annual-average and time-matched Scope 2 varies significantly depending on when and where you consume:
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.
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 location-based Scope 2 figure.
gridIQ automates the entire process. Upload a NEM12 meter file or CSV of your interval data, select your region (NEM or WEM), and get both methods side by side: a location-based figure time-matched to half-hourly grid intensity, and a market-based figure built from the EAC instruments (LGCs, GreenPower) or PPA you hold. The grid carbon intensity is matched to each interval automatically using actual generation mix data for your region. Export as PDF for your sustainability report.
Every gridIQ account includes a 21-day Pro trial with full access to the Scope 2 emissions tracker, supporting mandatory climate reporting Australia 2026 disclosure requirements. After the trial, the Scope 2 tracker is available on Pro at $499/month ($399/month billed annually).
Try our free Scope 2 emissions calculator for a quick estimate, or create your account for full interval-level time-matched Scope 2 tracking.