Energy balances

Domestic energy supply is derived from either indigenous production or imported from overseas sources. In turn, energy types can be transformed into different forms of energy at the cost of losses and inefficiencies, which vary by the transformation process used. Supply, demand, losses, and inefficiencies are reflected in balanced energy supply and demand tables.

Both the energy supply and demand sections of the energy balance tables are calculated from surveys that span different sources. An imbalance exists between demand calculated from reported supply data, and demand observed from reported consumption data.

Energy supply

Total primary energy supply (TPES) is the amount of energy available for use in New Zealand. Much of it is converted into other forms of energy before it is used.

By convention, fuel used for international transport is excluded from TPES. International transport includes international sea and air transport but excludes coastal shipping, national air transport, and all land transport.

Indigenous natural gas production does not include natural gas that is flared, reinjected, or extracted as liquefied petroleum gas (LPG). The primary energy figures presented are actual data, except for some that go into electricity generation as detailed under energy transformation.

Energy transformation

Energy transformation includes:

• generation of electricity, including cogeneration
• oil production, including refining operations and the manufacture of synthetic fuel from natural gas (Methanex stopped the production of methanol to petrol in April 1999)
• other transformation, primarily steel production.

In the Energy Transformation section of the balance tables, ‘energy in’ is shown as negative values and ‘energy out’ as positive values in the appropriate columns. Transformation of energy from one form to another always results in conversion losses, particularly in thermal electricity generation, as much energy is lost as heat.

Conversion losses in electricity generation are calculated using the net electricity generated, with the actual input being used where available. The efficiency factors shown in Table B.1 are used otherwise. Input to electricity generation from biogas, hydro, wind, and waste heat are fully estimated. Quarterly figures for electricity generation are made up of actual data from major generators and the Electricity Authority. Estimates are made where actual data are unavailable at the time of publishing.

Table B.1: Default electrical transformation efficiency factors

Liquid biofuel production (bioethanol and biodiesel) appears as renewable energy supply in the energy balance tables. As bioethanol and biodiesel are generally blended with motor petrol and diesel before consumption, liquid biofuel also appears in Energy Transformation under Fuel Production.

Losses and own use in the energy balances include:

• losses before and after transformation
• losses and own use in production
• transmission and distribution losses
• electricity industry own use—electricity used on-site at power stations
• oil industry losses and own use — distribution tankage losses, stocks, accounts adjustment, and own consumption.

Transformation losses are excluded.

Non-energy use is primary energy used for purposes other than combustion. For example, bitumen used in road construction, and natural gas used as chemical feedstock in the production of methanol and ammonia or urea.

How we treat solar photovoltaic panels

Estimates of the amount of electricity generated using solar photovoltaics (PV) are included in the energy balance tables in this edition of Energy in New Zealand. The TPES of solar is the sum of the direct use of solar thermal (for hot water heating), and the amount of solar energy directly converted into electricity using PV panels.

Solar PV electricity generation is estimated using data on the total installed capacity of grid‑connected solar PV installations in New Zealand. This is converted to output using an assumed annual capacity factor of 14% — the solar panels produce their full output 14% of the time. The capacity factor is then scaled using data on sunshine hours from the National Institute of Water and Atmospheric Research (NIWA) to introduce seasonal variation. Consumption of solar thermal is included in the demand section of the energy balance table under Renewables – Solar, whereas the consumption of electricity generated by solar PV panels appears under Electricity. Solar PV consumption by sector is allocated using data from the Electricity Authority.

Consumer energy demand

Consumer energy is the amount of energy consumed by final users. It excludes energy used or lost in the process of transforming energy into other forms and in bringing the energy to the final consumers. For example, natural gas is a primary energy source, some of which is transformed into electricity, of which some is lost in transmission to consumers.

Consumer energy statistics can be either calculated from supply-side data or observed from usage data.

• Consumer energy (calculated) forms the top half of the energy balance tables. It is calculated as TPES less energy transformation less non-energy use.
• Consumer energy (observed) forms the bottom half of the energy balance tables. It represents reported demand in the agricultural, industrial, commercial, transport, and residential sectors. With the exception of domestic use of energy for on-road, rail, sea, and air transport in the transport sector, these sectors follow the Australia New Zealand Standard Industrial Classification 2006 definitions. Estimates of on-site cogeneration demand are included in electricity end use.

Where the energy end-use is not available or confidential, the ‘unallocated’ category is used.

Statistical differences

Statistical differences show the difference between ‘consumer energy (calculated)’ and ‘consumer energy (observed)’. This difference is shown at the bottom of the energy balance tables.

Energy balance table

Energy balance table [XLSX, 2.1 MB]

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