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 2021, and the annual time series extends back to 2011. There is also an equivalent 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

In this edition, a new method of calculating the purchased electricity, and transmission and distribution loss emission factors are adopted. Previously, the factor was calculated as the difference between the generation and consumption emission factors. This new method directly uses MBIE’s transmission and distribution line losses data, to more accurately reflect actual losses on the electricity grid.

As a result, the emission factor for transmission and distribution losses has decreased by 38 per cent from the previous edition.

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 9 and table 10 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 9.

Table 9: Emission factor for purchased grid-average electricity – annual average

Table 5.1: An entity uses 1,400 kg of LPG to heat an office building in the reporting year.

	Emission Factor (Kg CO2e/Kg)	Calculation	Emissions (Kg CO2e)
Gas
CO2	2.963726	1400.0 x 4149.22	4149.22
CH4	0.006650	1400.0 x 9.31	9.31
N2O	0.001259	1400.0 x 1.76	1.76
Total_CO2e	2.971635	1400.0 x 4160.29	4160.29

The emission factors for the calendar quarters (quarter end) for 2021–2023 purchased electricity from the New Zealand grid are in Table 10.

Table 5.2: An entity uses 1,400 kg of LPG to heat an office building in the reporting year.

	Emission Factor (Kg CO2e/Kg)	Calculation	Emissions (Kg CO2e)
Gas
CO2	2.963726	1400.0 x 4149.22	4149.22
CH4	0.006650	1400.0 x 9.31	9.31
N2O	0.001259	1400.0 x 1.76	1.76
Total_CO2e	2.971635	1400.0 x 4160.29	4160.29

Table 10: Emission factor for purchased grid-average electricity – calendar quarters

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 (section 2), this means:

E = emissions from the emissions source in kg CO2-e per year

Q = quantity of electricity used (kWh)

F = emission factors from Table 9 or Table 10.

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.

PURCHASED ELECTRICITY: EXAMPLE CALCULATION

An entity wants to report on its Scope 1 fuel emissions (in kg CO₂-e/litre) from a specific biodiesel blend of 10 per cent. It is known that:

mineral diesel emission factor = 8888 kg CO₂-e/litre
biodiesel emission factor = 9999 kg CO₂-e/litre

Therefore, 10 per cent biodiesel blend emission factor = (10% × 8888) + [(1-10%) × 9999] = 7777 CO₂-e/litre biofuel blend

Note: Numbers may not add due to rounding.

5.2.2 Emission factor derivation methodology

Table 5.3: An entity uses 1,400 kg of LPG to heat an office building in the reporting year.

	Emission Factor (Kg CO2e/Kg)	Calculation	Emissions (Kg CO2e)
Gas
CO2	2.963726	1400.0 x 4149.22	4149.22
CH4	0.006650	1400.0 x 9.31	9.31
N2O	0.001259	1400.0 x 1.76	1.76
Total_CO2e	2.971635	1400.0 x 4160.29	4160.29

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 9 and Table 10 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 12 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)¹

Table 12 shows the emission factors for transmission and distribution losses from the national grid.

Table 5.4: An entity uses 1,400 kg of LPG to heat an office building in the reporting year.

	Emission Factor (Kg CO2e/Kg)	Calculation	Emissions (Kg CO2e)
Gas
CO2	2.963726	1400.0 x 4149.22	4149.22
CH4	0.006650	1400.0 x 9.31	9.31
N2O	0.001259	1400.0 x 1.76	1.76
Total_CO2e	2.971635	1400.0 x 4160.29	4160.29

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 section 2, this means:

E = emissions from the emissions source in kg CO2-e per year

Q = quantity of electricity used (kWh)

F = emission factors from Table 12

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.

PURCHASED ELECTRICITY: EXAMPLE CALCULATION

An entity wants to report on its Scope 1 fuel emissions (in kg CO₂-e/litre) from a specific biodiesel blend of 10 per cent. It is known that:

mineral diesel emission factor = 8888 kg CO₂-e/litre
biodiesel emission factor = 9999 kg CO₂-e/litre

Therefore, 10 per cent biodiesel blend emission factor = (10% × 8888) + [(1-10%) × 9999] = 7777 CO₂-e/litre biofuel blend

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 9.

5.3.2 Emission factor derivation methodology

In previous editions of this guide, MBIE’s electricity consumption data series was used to calculate the consumption emission factor, which in turn was used to calculate the transmission and distribution loss factor.

In this new methodology, with emission factors provided directly by MBIE, actual transmission and distribution losses data are used, which more accurately reflect 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.

Footnotes

https://ghgprotocol.org/sites/default/files/standards/Scope%202%20Guidance_Final_Sept26.pdf↩︎