Australian Emission Factors Explained: NGA Factors, State Grid Differences, and Why They Matter

Victoria's Scope 2 emission factor is 0.78 kg CO2-e per kWh. Tasmania's is 0.20. Same country. Same reporting framework. Almost four times the difference.

If you've got sites in both states and you're applying a single national average factor — 0.62 — to everything, your Victorian sites are understated and your Tasmanian sites are wildly overstated. That's not a rounding error. It's the kind of mistake that lands you in trouble when an auditor pulls your NGER report apart, or when your ASRS disclosures go under limited assurance and the numbers don't reconcile.

The source of truth for emission factors in Australia is the NGA Factors workbook, published annually by DCCEEW (the Department of Climate Change, Energy, the Environment and Water). Every NGER reporter and every entity reporting under AASB S2 needs these numbers. And yet, we keep seeing sustainability teams use outdated factors, wrong factors, or the national average when they should be using state-based ones. This is the article we wish someone had written for us when we were building Carbonly's emission calculation engine — a plain-English walkthrough of how Australian emission factors actually work, what changed in the 2025 edition, and the specific traps that catch people.

What the NGA Factors Workbook Actually Is

The National Greenhouse Accounts Factors workbook is a spreadsheet. That's it. Not a regulation, not a standard, not a 300-page policy document. It's an Excel file published each year by DCCEEW containing the emission factors and calculation methods that Australian organisations use to estimate greenhouse gas emissions.

But don't let the simplicity fool you. The factors inside it are the product of a massive national inventory exercise. They're derived from AEMO generation data, fuel composition analysis, and methodologies consistent with IPCC guidelines — reviewed by international experts annually. When you plug a number from the NGA Factors workbook into your emissions calculation, you're using the same factors that feed into Australia's official national inventory reported to the United Nations Framework Convention on Climate Change.

The workbook covers far more than electricity. It includes factors for stationary energy (natural gas, diesel, LPG), transport fuels, fugitive emissions, industrial processes, waste, and agriculture. For most commercial and industrial businesses, though, the electricity emission factors in Table 1 and Table 2 are where you'll spend 90% of your time.

The 2025 edition — which applies to NGER reports for the 2025-26 reporting year — replaced the 2024 workbook. If you're still using 2024 factors for your current reporting, stop. The factors change every year, and using the wrong edition is one of the most common errors the Clean Energy Regulator flags.

State-Based Electricity Emission Factors: The Numbers

Here's the part most people come to this article for. These are the location-based Scope 2 emission factors from the NGA Factors 2025 workbook (Table 1), expressed in kg CO2-e per kWh of electricity consumed from the grid.

State/Territory	Scope 2 Factor (kg CO2-e/kWh)	Scope 3 Factor (kg CO2-e/kWh)	Combined
NSW & ACT	0.64	0.03	0.67
Victoria	0.78	0.09	0.87
Queensland	0.67	0.09	0.76
South Australia	0.22	0.04	0.26
WA (SWIS)	0.50	0.06	0.56
WA (NWIS)	0.56	0.09	0.65
Tasmania	0.20	0.03	0.23
NT (DKIS)	0.56	0.09	0.65
National Average	0.62	0.07	0.69

Source: DCCEEW, National Greenhouse Accounts Factors 2025 workbook.

Three things jump out of this table. Victoria is the most carbon-intensive grid in Australia, and it isn't close. South Australia and Tasmania are dramatically cleaner. And the national average hides enormous variation.

We'll explain why. But first — what's the Scope 3 column doing there?

Scope 2 vs Scope 3 Electricity Factors: Two Different Things

This trips up more people than you'd expect. When you consume grid electricity, you generate both Scope 2 and Scope 3 emissions. They're not the same thing, and you shouldn't be adding them together into a single "electricity emissions" line in your report.

Scope 2 captures the emissions from generating the electricity. The coal burned at the power station. The gas turbine spinning. The actual combustion that produced CO2.

Scope 3 (for electricity) captures the emissions from extracting and transporting the fuel to the power station, plus the electricity lost in transmission and distribution between the generator and your meter. Think of it as the upstream supply chain emissions of your electricity. The coal that was mined and trucked to the plant. The gas that was extracted and piped. The roughly 10% of electricity that dissipates as heat in the wires before it reaches your building.

For most Australian businesses, the Scope 3 electricity factor is small relative to Scope 2 — typically between 0.03 and 0.09 kg CO2-e/kWh. But it's not zero. And under ASRS, if you're reporting Scope 3 (mandatory from your second reporting year), these transmission and distribution losses need to be included.

Under NGER, you report Scope 2 electricity emissions. Under AASB S2 paragraph 29(a)(iv), you need Scope 1, 2, and 3 as separate line items. The NGA Factors workbook gives you both numbers, state by state. Use the right column for the right scope.

Why Victoria's Factor Is 0.78 and Tasmania's Is 0.20

The difference comes down to one thing: what powers the grid.

Victoria's electricity generation is still heavily dependent on brown coal from the Latrobe Valley. Brown coal is the most carbon-intensive fossil fuel used for electricity generation in Australia — individual brown coal plants emit between 1.0 and 1.2 kg CO2 per kWh generated. Even with growing renewable capacity, brown coal still accounted for a substantial share of Victoria's generation mix in 2024-25. That drags the state's average emission factor up to 0.78.

Tasmania is the opposite story. Hydro-electric generation supplies around 80% of the state's electricity, with wind contributing roughly 17% and solar filling most of the rest. Gas generation exists but runs rarely. The result is an emission factor of 0.20 — and even that isn't zero because hydro dams produce small amounts of methane from decomposing vegetation in reservoirs.

South Australia's 0.22 factor reflects its massive wind and solar buildout over the past decade. There are periods where SA's grid runs at close to 100% renewables. Queensland's 0.67 sits higher because of coal and gas-fired generation in the Gladstone and Callide regions, despite significant solar uptake.

The practical takeaway: if you're a property manager or construction company with sites in multiple states, applying the national average of 0.62 to every site introduces systematic error. Your Victorian sites will look better than they are. Your South Australian and Tasmanian sites will look worse. Neither is accurate, and an NGER auditor checking your calculation methodology will catch it.

We wrote a detailed walkthrough of how to apply these factors to actual electricity bills in our guide on calculating Scope 2 emissions from electricity bills. That article covers finding consumption on retailer invoices, unit conversions, and worked examples.

Factors Change Every Year. Use the Right One.

The NGA Factors workbook is updated annually, and the numbers move. Sometimes noticeably.

Compare 2024-25 factors with 2025-26 for the same states:

NSW: 0.66 down to 0.64
Victoria: 0.77 up to 0.78
Queensland: 0.71 down to 0.67
Tasmania: 0.15 up to 0.20
SA: 0.23 down to 0.22

Queensland dropped by 0.04 in a single year — that's a 6% reduction in grid carbon intensity, largely driven by new solar capacity. Tasmania went the other direction, from 0.15 to 0.20, a 33% increase. That's probably counter-intuitive for a state that's almost entirely renewable. The explanation lies in methodology changes. DCCEEW discontinued the three-year averaging approach for electricity emission factors in September 2024, switching to AEMO NEM-Review data for the specific reporting period. Single-year data is more volatile, and any year where Tasmania imports more electricity from Victoria via Basslink, or where hydro generation dips due to lower rainfall, the factor jumps.

This matters for trend analysis. If your emissions went up year-on-year, it might be because you consumed more electricity — or it might be because the emission factor changed. Your ASRS disclosure needs to explain material movements. Knowing that Tasmania's factor jumped 33% between editions means you can explain the variance without pretending your operations got dirtier.

The rule is simple: use the factors from the edition that applies to your reporting period. For NGER reports due 31 October 2026 (covering the 2025-26 financial year), use the NGA Factors 2025 workbook. Don't mix editions across sites or periods.

Location-Based vs Market-Based: The Reporting Split

This is where it gets a bit complicated — and where we're honest that the rules are still settling.

Under AASB S2 paragraph 29(a)(v), entities must report location-based Scope 2 emissions. That's the state-based grid factor from Table 1 of the NGA Factors workbook. No choice involved. Location-based is mandatory.

Market-based reporting is voluntary under ASRS. If you've bought GreenPower, surrendered Large-scale Generation Certificates (LGCs), or signed a renewable Power Purchase Agreement (PPA), you can report market-based Scope 2 as a supplementary disclosure alongside your location-based figure. But you can't replace the location-based number with it.

For NGER, a voluntary market-based method has been available since 2023-24. The Clean Energy Regulator published an updated guideline in August 2025. The key concept is the Residual Mix Factor (RMF) — and this is the number that catches people off guard.

The national RMF in the NGA Factors 2025 workbook is 0.81 kg CO2-e/kWh. That's higher than the national location-based average of 0.62. Why? Because the RMF strips out the zero-emissions electricity that someone else has already claimed via LGCs or GreenPower. What's left — the residual mix — is dirtier than the grid average. So if you haven't purchased any renewable energy instruments, your market-based Scope 2 is actually higher than your location-based Scope 2. State-level RMFs were introduced for 2025-26 reporting, adding more granularity.

We're not sure the market-based method is well understood yet by most reporters. The CER's Q3 2025 data showed 5.3 million non-RET LGC cancellations linked to just 47 NGER reporters. That's out of 961 registered controlling corporations. So fewer than 5% of NGER reporters are actively using contractual instruments for market-based claims. For the other 95%, the location-based method is the only game in town.

AR5 vs AR6 Global Warming Potentials: The Technical Gotcha

Here's a detail that matters more than most people realise, especially if you report under both NGER and ASRS.

Emission factors convert activity data (like kWh or litres of fuel) into CO2-equivalent emissions. But CO2-equivalent is itself a conversion — it uses Global Warming Potential (GWP) values to express methane, nitrous oxide, and other gases as a CO2 equivalent. Different IPCC Assessment Reports assign different GWP values to the same gas.

The key GWP-100 values:

IPCC AR5 (2013): Methane (CH4) = 28. Nitrous oxide (N2O) = 265.

IPCC AR6 (2021): Methane (CH4) = 27.9. Nitrous oxide (N2O) = 273. Fossil-source methane = 29.8.

NGER uses AR5 GWP values. The NGA Factors workbook is built on AR5. This is what you use for your NGER report.

AASB S2 requires AR6 GWP values — it follows the ISSB standard, which adopted AR6.

For electricity Scope 2, this difference is minimal because electricity emission factors are already expressed in CO2-e and predominantly reflect CO2 from combustion. The GWP matters more for Scope 1 emissions involving methane (fugitive emissions, livestock, landfill gas) or nitrous oxide (fertiliser application, wastewater). Nitrous oxide went from 265 to 273 between AR5 and AR6 — a 3% increase. That means the same quantity of N2O emissions produces a higher CO2-e figure under AR6 than AR5.

The practical problem: if you prepare your NGER report using AR5-based NGA Factors and then try to reuse those numbers directly in your ASRS disclosure, your methane- and N2O-heavy emission sources will be slightly understated under AASB S2's AR6 requirement. For a company with significant fugitive emissions or agricultural operations, this isn't trivial.

AASB has acknowledged this tension. Their December 2025 amendments to AASB S2 included implementation relief measures, and the NGER Act's methodology is explicitly recognised as an acceptable starting point for ASRS calculations. But you may need to apply GWP conversion adjustments for Scope 1 sources where the gas mix matters. For pure electricity Scope 2, you're probably fine using NGA Factors directly.

If you're an NGER reporter being pulled into ASRS Group 2 automatically via the registration pathway, this is one of the technical adjustments you need to plan for. It isn't hard — it's a multiplication factor adjustment on specific emission sources. But you need to know it exists.

Common Mistakes We Keep Seeing

We built Carbonly's emission calculation engine to handle these edge cases automatically, and the reason we know about them is that we kept finding them in real data. Here are the ones that come up most.

Using last year's factors for this year's report. The NGA Factors workbook is updated annually. The 2025 edition applies to 2025-26 NGER reports. Using 2024 factors for a 2025-26 reporting period is non-compliant and will be flagged in an audit.

Applying the national average instead of state factors. We mentioned this at the top, but it's worth repeating. The national average of 0.62 is useful for rough estimates. It's not acceptable for NGER reporting or ASRS disclosure if you know the location of your electricity consumption — and you do, because it's on the bill.

Forgetting Scope 3 electricity factors exist. When people say "electricity emission factor," they usually mean the Scope 2 number. But the NGA Factors workbook also provides a Scope 3 factor for transmission and distribution losses. Under ASRS, you need to report Scope 3 from your second year onwards. Under NGER, Scope 3 isn't required — but if you're dual reporting, you need to account for it separately.

Confusing WA grids. Western Australia has two separate grids: SWIS (South West Interconnected System, covering Perth and surrounds) and NWIS (North West Interconnected System, covering the Pilbara). They have different emission factors — 0.50 vs 0.56. If your WA sites are in the Pilbara and you're using the SWIS factor, your numbers are wrong.

Mixing up kWh and MWh. The NGA Factors are expressed in kg CO2-e per kWh. Your electricity bill might show consumption in kWh, but NGER reporting requires tonnes CO2-e. That's two conversions: kWh to the emission factor multiplication, then kilograms to tonnes (divide by 1,000). Sounds obvious, but a misplaced decimal across 50 sites becomes a material error fast. The ANAO found that 72% of 545 NGER reports it examined contained errors — many of them unit conversion issues.

Where Emission Factors Come From (and Why You Should Care)

It's worth understanding the supply chain behind these numbers, because it affects how confident you can be in them.

DCCEEW calculates electricity emission factors using generation data from AEMO (the Australian Energy Market Operator). For states in the NEM — NSW, Victoria, Queensland, SA, Tasmania, and the ACT — this data comes from NEM-Review, which tracks real-time generation output by fuel type across the grid. For WA and the NT, which operate outside the NEM, the methodology uses state-specific data sources.

The factor for each state represents the average emissions intensity of electricity consumed in that state during the financial year. It accounts for interstate electricity flows — Tasmania imports from Victoria via Basslink, SA imports from and exports to Victoria and NSW. If Tasmania imports carbon-intensive Victorian power during a dry year, Tasmania's emission factor goes up even though no Tasmanian generator burned more fuel.

This is also why three-year averaging was used historically — it smoothed out year-to-year volatility from variable hydro output, interconnector flows, and weather-dependent renewable generation. DCCEEW dropped that approach in September 2024, meaning factors now reflect single-year data and will be more volatile. The Tasmania jump from 0.15 to 0.20 is an early example of this volatility in action.

For non-electricity factors — natural gas, transport fuels, waste — the methodology is different. Fuel-specific emission factors are based on the carbon content and combustion characteristics of each fuel, calibrated to Australian fuel composition data. These change less frequently than electricity factors, but they do update. The 2025 workbook added Scope 1 emission factors for hydrogen combustion for the first time, reflecting the emerging hydrogen economy.

Using This in Practice

If you're a sustainability analyst preparing an NGER report or an ASRS disclosure, here's what to do.

Download the NGA Factors 2025 workbook from the DCCEEW website. Open Table 1 for location-based electricity factors. Match each site to its state or grid zone. Multiply each site's kWh consumption by the corresponding factor. Record the Scope 2 and Scope 3 figures separately.

For fuel-based Scope 1 emissions — natural gas, diesel, LPG — use the relevant tables in the same workbook. Pay attention to the units. Natural gas factors are expressed per GJ, not per cubic metre or per kWh. You'll need to convert your gas bill consumption into GJ using the heating value specified by your retailer.

If you're reporting under both NGER and ASRS, use the NGA Factors for your NGER calculations. Then review whether your Scope 1 sources include significant methane or N2O emissions. If they do, apply the AR6 GWP adjustment for your ASRS disclosure. If your emissions are predominantly CO2 from electricity and fuel combustion, the AR5/AR6 difference is negligible and the NGA Factors can serve both reports.

And if you're managing more than about 20 sites or 50 utility bills per quarter — this is the kind of thing that should be automated, not done in a spreadsheet where someone can accidentally drag the wrong factor into 15 rows. We built Carbonly with the NGA Factors 2025 embedded in our calculation engine, matched to each site's state automatically. But whether you use our platform or another, the principle is the same: get the factors right, match them to the right state, and use the right edition for your reporting period.

The NGA Factors workbook is free. The data is public. The methodology is transparent. There's no excuse for getting this wrong — but people do, every reporting cycle. Don't be one of them.

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