Grid Electricity — Western Australia (NWIS)

The Pilbara powers a fair chunk of the global iron ore trade, and it does so on its own grid: the North Western Interconnected System (NWIS). If your operation buys electricity on this network, every kilowatt hour adds 0.56 kg CO₂-e to your scope 2 emissions — a different factor from Perth’s SWIS, and a distinction that matters for any WA reporter with sites on both networks.

The common mistake is applying a single “WA factor” state-wide. There isn’t one: the NGA Factors publish separate values for the SWIS (0.50) and the NWIS (0.56). For 2025–26 the NWIS location-based factor is 0.56 kg CO₂-e/kWh, with a paired scope 3 loss factor of 0.09 kg CO₂-e/kWh reported separately.

Quick Verdict

Grid electricity consumed on Western Australia’s North Western Interconnected System (NWIS) — the Pilbara network — has a location-based scope 2 emission factor of 0.56 kg CO₂-e per kWh for 2025–26, per Table 1 of the Australian National Greenhouse Accounts Factors 2025 (DCCEEW). It applies to any organisation purchasing electricity on the NWIS, regardless of supplier. A separate scope 3 factor of 0.09 kg CO₂-e/kWh covers transmission and distribution losses and is reported under scope 3, not added to scope 2. The NWIS sits just below the national average of 0.62 and above the SWIS at 0.50. Fuel burned in your own on-site generators is scope 1 and uses fuel factors, not this one.

How to Calculate WA NWIS Electricity Emissions

Emissions (kg CO₂-e) = Electricity consumed (kWh) × 0.56

Worked Example 1: Average household

Assume an average household consuming around 5,000 kWh a year (an illustrative assumption — check your own bills).

5,000 kWh × 0.56 kg CO₂-e/kWh = 2,800 kg CO₂-e

2.8 tonnes CO₂-e (Scope 2)

Worked Example 2: Accommodation camp

A Pilbara accommodation camp consumes 850 MWh (850,000 kWh) over the reporting year.

850,000 kWh × 0.56 kg CO₂-e/kWh = 476,000 kg CO₂-e

476 tonnes CO₂-e (Scope 2)

Network losses are reported separately: 850,000 kWh × 0.09 kg CO₂-e/kWh = 76,500 kg CO₂-e = 76.5 tonnes CO₂-e (Scope 3).

Worked Example 3: Processing facility

A minerals processing facility consumes 6 GWh (6,000,000 kWh) a year from the NWIS.

6,000,000 kWh × 0.56 kg CO₂-e/kWh = 3,360,000 kg CO₂-e

3,360 tonnes CO₂-e (Scope 2)

Run your own consumption through a scope 2 location-based calculator, or track it continuously with an electricity and energy dashboard.

How the NWIS Compares to Other States

Calculation Methodology: How These Factors Work

Electricity emission factors have more moving parts than fuel factors, and getting the methodology right matters for both NGER and AASB S2. Here is how the NGA Factors 2025 intends these numbers to be used.

The scope 2 and scope 3 components

Every unit of grid electricity you consume carries two separate emission factors that are reported separately:

• Scope 2 (0.56 kg CO₂-e/kWh) covers the emissions from generating the electricity you actually consumed — the indirect emissions from power stations feeding the grid in the WA North Western Interconnected System (NWIS).
• Scope 3 (0.09 kg CO₂-e/kWh) covers electricity lost in transmission and distribution before it reached you. Generators had to produce more than you metered, and the emissions from that lost share are yours to report under scope 3.

The NGA Factors formula combines both:

Y = Q × (EF2 + EF3) ÷ 1,000

where Y is total emissions in tonnes CO₂-e, Q is electricity consumed in kWh, and EF2 and EF3 are the factors above. For the WA North Western Interconnected System (NWIS): Q × (0.56 + 0.09) ÷ 1,000 — but keep the two results separate in your inventory, because scope 2 and scope 3 are disclosed as different line items.

Location-based method

The factor on this page is a location-based factor. It reflects the physical emissions intensity of generation in the WA North Western Interconnected System (NWIS), recalculated each financial year from actual generation data, interstate electricity flows where they exist, methane emissions from hydro dams, and after deducting self-consumed rooftop solar. It answers the question: what were the emissions of the grid I physically drew from? Your electricity contract makes no difference to a location-based figure — GreenPower, carbon-neutral plans and power purchase agreements do not change it.

Market-based method

The market-based method answers a different question: what have I contracted for? It assigns an emission factor of zero to renewable electricity you have genuinely claimed, and applies the national residual mix factor — 0.81 kg CO₂-e/kWh (scope 2) plus 0.11 kg CO₂-e/kWh (scope 3) for 2025 — to everything else. The residual mix is deliberately higher than most location-based factors because the renewable share already claimed by others is stripped out of it.

Under the NGA market-based formula, your consumption is reduced by:

• The Renewable Power Percentage (RPP) — the share of grid electricity covered by the Large-scale Renewable Energy Target on everyone’s behalf. For the 2025 financial year this is 18.195% (the average of the published 2024 and 2025 calendar-year RPPs). You get this reduction automatically, with no action required.
• Voluntarily surrendered Large-scale Generation Certificates (LGCs) — each surrendered LGC (with a generation date within 36 months of the end of the reporting year) zero-rates 1 MWh. This is how corporate renewable PPAs are recognised.
• Accredited GreenPower purchases — buying GreenPower from an accredited provider counts as an eligible renewable energy certificate surrender for the purchased volume.
• On-site generation — renewable electricity you generate and consume behind the meter never enters the calculation (it reduces Q), and LGCs created for on-site generation you consumed are netted out so they are not double-counted.

Worked contrast: 100% GreenPower

Take 1,000,000 kWh consumed in the WA North Western Interconnected System (NWIS):

• Location-based: 1,000,000 × 0.56 ÷ 1,000 = 560 t CO₂-e (Scope 2), regardless of contract.
• Market-based with 100% GreenPower: the full volume is zero-rated = 0 t CO₂-e (Scope 2).
• Market-based with no renewable purchases: roughly 1,000,000 × (1 − 0.18195) × 0.81 ÷ 1,000 ≈ 663 t CO₂-e (Scope 2) after the automatic RPP reduction, using the residual mix factor.

Which method should you use?

Report both. NGER reporting uses the location-based factors, while the GHG Protocol Scope 2 Guidance — which AASB S2 builds on — expects dual reporting: a location-based figure and a market-based figure side by side. The location-based number shows your physical footprint; the market-based number is where your renewable procurement shows up. NetNada calculates both views from the same consumption data.

NGER and AASB S2 Reporting

Many NWIS-connected operations exceed NGER thresholds and must report scope 2 electricity emissions to the Clean Energy Regulator using the correct network factor, while AASB S2 requires the same inventory in climate disclosures — with both location-based and market-based scope 2 figures where contractual instruments are held. NetNada’s NGER reporting tool applies the right factor per network automatically.