5  Purchased electricity, heat and steam emission factors

Purchased energy, in the form of electricity, heat or steam, is an indirect (Scope 2) emission. This section also includes transmission and distribution losses for purchased electricity, which is an indirect (Scope 3) emissions source.

Note that both the emission factor for purchased electricity and the emission factor for transmission and distribution line losses align with the definitions in the GHG Protocol.

In this guide, we have included a time series of historic electricity emission factors based on annual and quarterly periods. The quarterly time series extends back to March 2022, and the annual time series extends back to 2012. There is also an equivalent annual time series for transmission and distribution losses.

The guide provides information on reporting imported heat and steam and geothermal energy. It does not provide emission factors for these categories as they are unique to a specific site. Users could liaise directly with their supplier of the imported heat, steam, or geothermal energy, for supplier specific emissions intensities suitable for use in the entity inventory.

5.1 Overview of changes since previous update

Table 5.1: Summary of changes to purchased energy emission factors
Domain Emission factors Size of change Explanation for change
Purchased Energy Current/latest electricity factor 38.70% There is no change in methodology. The increase in the emissions factor can be attributed to shifting electricity generation dynamics. In 2022 and 2023, emissions from electricity generation were relatively low due to favourable weather conditions and strong hydro inflows. In contrast, 2024 saw an increase in the proportion of fossil-based generation. This rise impacts associated emissions factors, including Travel and Freight (for electric and PHEV vehicles), and Working from home emissions factors. The 38.7% change is calculated as the difference between the 'Electricity Used - 2023' emission factor, as published in the 2024 Measure Emissions Guide, and the 'Electricity Used - 2024' emission factor in this edition.
Transmission & distribution losses Electricity Transmission & distribution losses 9.30% Since the transmission and distribution (T&D) loss factors for 2024 were unavailable, a new methodology was adopted, using the average loss ratio of purchased energy over the 2011–2023 period. The Electricity Transmission & distribution losses factors are affected by the rise in Purchased Energy emissions factors.
Natural Gas Transmission & distribution losses -12.90% Estimated fugitive emissions from both natural gas distribution and transmission networks decreased in 2023 relative to 2022.

5.2 Indirect Scope 2 emissions from purchased electricity from the New Zealand grid – using the location-based method

This guide applies to electricity purchased from a supplier that sources electricity from the national grid (i.e, purchased electricity consumed by end users). It does not cover on-site, self-generated-electricity.

The grid-average emission factor best reflects the carbon dioxide equivalent emissions associated with the generation of a unit of electricity purchased from the national grid in New Zealand. We recommend the use of the emission factors in Table 5.2 and Table 5.3 for all electricity purchased from the national grid, apart from when a market-based method is being used.

The emission factor accounts for the emissions from fuel combustion at thermal power stations (ie, power stations which generate electricity by burning fossil fuels) and fugitive emissions from the generation of geothermal electricity.

The emission factor for purchased grid-average electricity does not include transmission and distribution losses. A separate average emission factor for this as an indirect (Scope 3) emission source is in Section 5.3

The provided emission factors are an average for the whole of New Zealand for a given quarter or year. The actual emissions produced for a given unit of electricity may differ depending on factors such as the time of year, time of day and geographical area.

Using quarterly emission factors accounts for the high seasonal variation seen in electricity emission factors. This variation is generally a result of the higher proportion of fossil-based electricity generation typically used in the winter months. Therefore, using an annual emission factor may over or underestimate your entity’s GHG emissions.

Detailed additional guidance on reporting electricity emissions is available in the GHG Protocol Scope 2 Guidance.

As with the fuels for stationary combustion emission factors, the electricity emission factors do not incorporate emissions associated with the extraction, production and transport of the fuels burnt to produce electricity.

The emission factors for the annual average purchased electricity based on annual generation from the New Zealand grid is in Table 5.2.

Table 5.2: Emission factors for purchased grid-average electricity – annual average
Emissions Source Unit kg CO₂–e/unit CO₂/unit (kg CO₂–e) CH₄/unit (kg CO₂–e) N₂O/unit (kg CO₂–e)
Annual Averages
Electricity Used – 2012 kWh 0.1729810303 0.1686935231 0.0039810528 0.0003064544
Electricity Used – 2013 kWh 0.1461825561 0.1417469878 0.0042331574 0.000202411
Electricity Used – 2014 kWh 0.1221241874 0.1176384026 0.0043305912 0.0001551936
Electricity Used – 2015 kWh 0.1168674104 0.1121866766 0.0045398643 0.0001408695
Electricity Used – 2016 kWh 0.0915447009 0.0873594028 0.0041121544 0.0000731438
Electricity Used – 2017 kWh 0.1031083889 0.0992217864 0.0038009348 0.0000856678
Electricity Used – 2018 kWh 0.097861135 0.0943356571 0.0034050511 0.0001204269
Electricity Used – 2019 kWh 0.1105547311 0.1073371928 0.0030453883 0.00017215
Electricity Used – 2020 kWh 0.1216915353 0.1185907619 0.0029089182 0.0001918553
Electricity Used – 2021 kWh 0.123323991 0.1202492404 0.0028198509 0.0002548997
Electricity Used – 2022 kWh 0.0818949105 0.0790391248 0.0027617069 0.0000940788
Electricity Used – 2023 kWh 0.0766302343 0.0741168037 0.0024372846 0.000076146
Electricity Used – 2024 kWh 0.1011189484 0.0981990601 0.0027303581 0.0001895301

The emission factors for the calendar quarters (quarter end) for 2022–2024 purchased electricity from the New Zealand grid are in Table 5.3.

Table 5.3: Emission factor for purchased grid-average electricity – calendar quarters
Emissions Source Unit kg CO₂–e/unit CO₂/unit (kg CO₂–e) CH₄/unit (kg CO₂–e) N₂O/unit (kg CO₂–e)
Quarterly Averages
Electricity Used – Mar–2022 kWh 0.1096907589 0.1067391622 0.0027958305 0.0001557663
Electricity Used – Jun–2022 kWh 0.1191587201 0.11610675 0.0028724637 0.0001795064
Electricity Used – Sep–2022 kWh 0.0620184374 0.059341421 0.002644798 0.0000322184
Electricity Used – Dec–2022 kWh 0.0394184247 0.0366552982 0.002746336 0.0000167905
Electricity Used – Mar–2023 kWh 0.0769630732 0.0742775535 0.0026301779 0.0000553419
Electricity Used – Jun–2023 kWh 0.0529274691 0.0508234695 0.0020790999 0.0000248997
Electricity Used – Sep–2023 kWh 0.1004640282 0.097897541 0.0024613023 0.000105185
Electricity Used – Dec–2023 kWh 0.074229804 0.0715148659 0.0025981717 0.0001167664
Electricity Used – Mar–2024 kWh 0.0893041532 0.0864942083 0.0026981896 0.0001117553
Electricity Used – Jun–2024 kWh 0.1365281823 0.1336055275 0.0026064576 0.0003161972
Electricity Used – Sep–2024 kWh 0.1324850764 0.1293692016 0.002824639 0.0002912359
Electricity Used – Dec–2024 kWh 0.0400047226 0.0371942488 0.0027919734 0.0000185005

5.2.1 GHG inventory development

To calculate the emissions from purchased electricity, first collect data on the quantity of electricity used during the period in kilowatt hours (kWh), then multiply this by the emission factor. Applying the equation E = Q x F this means:

  • E = emissions from the emissions source in kg CO2-e per year
  • Q = distance travelled by vehicle type (km)
  • F = emission factors for correlating vehicle type from Table 5.2 or Table 5.3.

All entities across sectors typically report emissions using data on the amount of electricity used during the reporting period. Quantified units of electricity consumed are preferable.

5.2.1.1 PURCHASED ELECTRICITY: EXAMPLE CALCULATION

An entity uses 800,000 kWh of electricity in the 2023 reporting period. Its indirect (Scope 2) emissions from electricity are:

Example calculation of purchased electricity emissions
Gas Calculation Emissions (kg CO₂-e)
CH₄ emissions 800,000 x 0.0024372846 kg CO₂-e per kWh 1,950 kg CO₂-e
CO₂ emissions 800,000 x 0.0741168037 kg CO₂-e per kWh 59,300 kg CO₂-e
N₂O emissions 800,000 x 0.000076146 kg CO₂-e per kWh 60.9 kg CO₂-e
Total CO₂-e emissions 800,000 x 0.0766302343 kg CO₂-e per kWh 61,300 kg CO₂-e

Note: Numbers may not add due to rounding.

5.2.2 Emission factor derivation methodology

MBIE calculated the generation emission factors based on emissions from the generation of public electricity and the amount of electricity generated.

Table 5.4 details the MBIE data provided to calculate the annual emission factors

Table 5.4: Information used to calculate the purchased electricity emission factor 2011-2023
Year Emissions of CO2 from public electricity generation (kt) Public electricity generation (GWh)
2011 5,823 41,975
2012 7,224 41,762
2013 5,981 40,916
2014 5,035 41,232
2015 4,872 41,881
2016 3,799 41,501
2017 4,315 41,850
2018 4,110 41,999
2019 4,674 42,278
2020 4,967 41,706
2021 4,962 41,682
2022 3,237 41,920
2023 3,055 41,917

5.2.3 Assumptions, limitations and uncertainties

Using an annual average grid emission factor for electricity will inevitably introduce a certain level of inaccuracy, as the generation mix varies depending on your geographical location, by time of day and time of year.

We derived the emission factors in Table 5.2 and Table 5.3 for purchased electricity from generation data rather than consumption data. This emission factor does not account for the emissions associated with the electricity lost in transmission and distribution on the way to the end user. Table 5.5 contains the emission factors for transmission and distribution line losses.

5.3 Transmission and distribution losses for electricity

The emission factor for transmission and distribution line losses accounts for the additional electricity generated to make up for electricity lost in the transmission and distribution network. Under the GHG Protocol, end users should report emissions from electricity consumed from a transmission and distribution system as an indirect (Scope 3) emission source. Electricity and distribution companies should however report these losses as indirect (Scope 2) emissions.1.

Table 5.5 shows the emissions factors for transmission and distribution losses from the national grid.

Table 5.5: Transmission and distribution losses for electricity consumption
Emissions Source Unit kg CO₂–e/unit CO₂/unit (kg CO₂–e) CH₄/unit (kg CO₂–e) N₂O/unit (kg CO₂–e)
Electricity Consumption
2012 kWh 0.0131555601 0.0128294865 0.0003027672 0.0000233065
2013 kWh 0.0111174815 0.0107801475 0.0003219403 0.0000153938
2014 kWh 0.0092877935 0.0089466404 0.0003293503 0.0000118028
2015 kWh 0.0088880049 0.0085320255 0.0003452659 0.0000107134
2016 kWh 0.0069621612 0.0066438607 0.0003127377 0.0000055627
2017 kWh 0.0078416032 0.0075460192 0.0002890688 0.0000065152
2018 kWh 0.0074425389 0.0071744191 0.0002589611 0.0000091587
2019 kWh 0.0084079128 0.0081632124 0.000231608 0.0000130924
2020 kWh 0.0092548894 0.0090190693 0.0002212292 0.000014591
2021 kWh 0.009379041 0.0091452 0.0002144554 0.0000193856
2022 kWh 0.006228275 0.0060110866 0.0002100334 0.0000071549
2023 kWh 0.0058278856 0.0056367341 0.0001853605 0.0000057911
2024 kWh 0.0076903022 0.0074682388 0.0002076493 0.0000144142

5.3.1 GHG inventory development

To calculate the emissions from transmission and distribution losses for purchased electricity, collect data on the quantity of electricity used during the period in kilowatt hours (kWh) and multiply this by the emission factor. Applying the equation E = Q x F this means:

  • E = emissions from the emissions source in kg CO2-e per year
  • Q = distance travelled by vehicle type (km)
  • F = emission factors for correlating vehicle type from Table 5.5.

5.3.1.1 TRANSMISSION AND DISTRIBUTION LOSSES: EXAMPLE CALCULATION

An entity uses 800,000 kWh of electricity in the 2023 reporting period. Its indirect (Scope 3) emissions from transmission and distribution losses for purchased electricity are:

Example calculation of emissions from Transimission and Distribution Losses for purchased electricity
Gas Calculation Emissions (kg CO₂-e)
CH₄ emissions 800,000 x 0.0001853605 kg CO₂-e per kWh 148 kg CO₂-e
CO₂ emissions 800,000 x 0.0056367341 kg CO₂-e per kWh 4,510 kg CO₂-e
N₂O emissions 800,000 x 0.0000057911 kg CO₂-e per kWh 4.63 kg CO₂-e
Total CO₂-e emissions 800,000 x 0.0058278856 kg CO₂-e per kWh 4,660 kg CO₂-e

Note: Numbers may not add due to rounding.

Alternatively, if your electricity provider gives a breakdown of the transmission and distribution losses this consumption data can be multiplied by a grid-average electricity emission factor from Table 5.2

5.3.2 Emission factor derivation methodology

Emission factors provided directly by MBIE, which uses actual transmission and distribution losses data, resulting in the emission factors more accurately reflect the actual losses on the electricity grid.

5.3.3 Assumptions, limitations and uncertainties

This emission factor covers grid-average electricity purchased by an end user. As with all emission factors for purchased electricity, we calculated those for transmission and distribution line losses as a national average.

As it is an average figure, the emission factor makes no allowance for distance from off-take point, or other factors that may vary between individual consumers.

This emission factor does not incorporate the emissions associated with the extraction, production and transport of the fuels burnt to produce the electricity.

5.4 Imported heat and steam

Entities that have a specific heat or steam external energy source (such as a district heating scheme) can calculate emissions using an emission factor specific to that scheme. This should be available from the owner of the external energy source.

5.5 Geothermal energy

Entities that have their own geothermal energy source can calculate emissions separately using a unique emission factor. Noting carbon emissions from geothermal power stations can be variable over time, this would consider factors such as the measured CO2 output from the production wells and the CO2 output at the surface, along with how the water by-product is used, for example, as industrial process heat.

Depending on the steam coming from the borehole, there may or may not be emissions associated with this energy type.

  1. GHG Protocol Scope 2 Guidance: https://ghgprotocol.org/sites/default/files/standards/Scope%202%20Guidance_Final_Sept26.pdf↩︎