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Glossary and references



Biodiesel can be produced from any vegetable oil or animal fat and used as a substitute or partial substitute for mineral diesel. To produce biodiesel, these fats or oils are chemically converted to esters that have properties similar to mineral diesel. Biodiesel is often blended with mineral diesel and blends of up to 5 percent in mineral diesel are suitable for use in diesel engines without modification.


Bioethanol is an alcohol made from sugar, starch and products containing sugars and starches, through a process of fermentation and distilling, and used as a substitute or partial substitute for petrol. Bioethanol has properties that are similar to petrol so it is often blended with petrol.


Biofuel is a generic term for fuels that can be produced from or are made up of a renewable material of plant or animal origin. Often they are substitutes or partial substitutes for fossil or mineral fuels. Biofuels used in transport are typically bioethanol which is used as a petrol substitute and biodiesel which is used as a diesel substitute. These are the biofuels that are most likely to be used in New Zealand in the medium term. Biofuels have the major advantage of not contributing to overall greenhouse gas emissions.


A combustible gas derived from decomposing biological waste. Biogas normally consists of 50 to 60 percent methane, plus carbon dioxide, and hydrogen sulfide

Bottled gas

Gas provided in a bottle or canister. This may be a large bottle or canister which is located near the house, which a contractor or wholesaler may remove and replace with new ones, a smaller bottle that is filled at a retail outlet, or canisters mainly used with camping and/or outdoor equipment.


A block of compressed coal dust, charcoal or sawdust and wood chips used for coal and kindling.


A hard black or brown rock comprised of mainly carbonised plant matter, that is burnt to provide heat.

Coal products

Any product made from coal and used for heating. Such as briquettes or coke.


The solid residue of impure carbon obtained from bituminous coal and other carbonaceous materials after removal of volatile material by destructive distillation. It is used as a domestic fuel and in the making of steel.

Compressed natural gas – CNG

A gas (mostly methane) used as a fuel, which is formed naturally in the earth when organic material decomposes under pressure and compressed to allow it to be stored and used for heating. Not readily available in New Zealand except in a few North Island service stations (for motor vehicle use only).

Diesel (petroleum diesel)

Petroleum diesel, also called petrodiesel or fossil diesel is produced from petroleum and is a hydrocarbon mixture, obtained in the fractional distillation of crude oil between 200° Celsius and 350° Celsius at atmospheric pressure.


A dwelling means any building or structure, or part thereof, that is used (or intended to be used) for the purpose of human habitation. It can be of a permanent or temporary nature and includes structures such as houses, motels, hotels, prisons, motor homes, huts and tents. There can be more than one dwelling within a building, such as an apartment building where each separate apartment or unit is considered a dwelling.


Electric power may be supplied by a central utility company to a residence via underground or above ground power lines or may be generated on site by solar panels, wind turbines, generators or other means, for the exclusive use of a residence.


A measure of being able to do work. There are many forms of energy, such as heat, mechanical, electrical, radiant, chemical and nuclear energies. The energy type for this standard is heat energy.

Energy source

The source of the energy, eg wood/coal burnt to obtain heat (and light).


Wood intended to be burned for heat.


Specifically, fuels is used to denote any solid or liquid material (eg coal, wood, oil, or gas, that is used as a source of heat or power).

Home heating oil

Home heating oil is diesel. In the past up to 10 percent kerosene was added to the diesel to prevent 'waxing' (solidifying) in very cold temperatures, however, due to the recent changes to the New Zealand diesel fuel specifications (reduction in sulphur content to a maximum of 50 mg/kg), fuel suppliers can no longer supply diesel fuel for use in diesel engines or home heating that is dosed with kerosene.

Liquefied Petroleum gas – LPG

Liquefied Petroleum Gas (LPG) is the generic name for mixtures of hydrocarbons (mainly propane and butane) in a liquid state. LPG is colourless, odourless and heavier than air. A chemical is added to give it a distinctive and unpleasant smell, sometimes described as rotten cabbage, so that even a very small leak can be easily detected. LPG burns readily in air and is an excellent fuel for heating, cooking and for automotive use.

Mains gas

Gas connected to the dwelling by underground pipes and provided on a continuous basis (never runs out). This includes new subdivisions where gas is reticulated form a central gas supply.

Natural gas

Natural gas consists mainly of methane. The large proportion of methane is one of the reasons natural gas has such a good safety record. Methane is lighter than air and will disperse more easily if there is a gas leak.

Passive solar heating

Specifically designed heating systems that are built into a dwelling, designed to capture the sun's heat during the day and to release it at night. This can include specifically built heat soak walls and other structures.


Wood pellets are a densified wood fuel typically made of shavings and/or sawdust. The sawdust or shavings are processed through an extruder to develop a uniform 1cm long pellet with diameter of 6mm. The pellets are bagged for residential use or trucked bulk for larger scale consumers.

Private dwelling

A private dwelling accommodates a person or a group of people. It is not generally available for public use. The main purpose of a private dwelling is as a place of habitation, and it is usually built (or converted) to function as a self contained housing unit.

Retail outlet

Store selling merchandise and/or services directly to the public in unlimited quantities.

Solar energy

Solar concentrators accurately oriented towards the sun directly convert the sun’s radiation into electrical energy by an array of photoelectric cells or solar cells.

Solar heating

A means by which solar energy is used as a source of heat. Solar energy may be translated directly via slate tiles or walls specifically designed to store heat, or may be accessed via some form of solar heating system. Excluded are windows or other non-specifically designed means of utilising solar energy.

Solar heating system

Specifically designed heating systems that rely on a solar energy source. Solar heating systems may be used to heat space or to heat water.


Any wooden material that may be burnt to provide heat.

Wood products

Any product made from wood and used for heating. Examples include pellets (defined elsewhere), charcoal and compressed sawdust logs.

Residual categories

Don’t know

Use of this category is discretionary. The use of a category capturing ‘don't know’ responses is most applicable to household surveys where don't know may be a legitimate response to certain questions.

Not elsewhere classified (nec)

This is a residual category used for responses for which no appropriate category exists. Such responses are usually infrequent or unanticipated.

Not further defined (nfd)

This is used in hierarchical classifications for responses containing insufficient detail to be classified to the most detailed level of the classification, but which can be classified to a less detailed category further up the hierarchy.

Refused to answer

This category is only used when it is known that the respondent has purposefully chosen not to respond to the question. Use of this residual category in processing is optional. Its use is most applicable in face-to-face or telephone interviews, but may be used in self-completed questionnaires if the respondent has clearly indicated they refuse or object to answering the question.

Response unidentifiable

This category is used when there is a response given, but:

  • the response is illegible, or
  • it is unclear what the meaning or intent of the response is – this most commonly occurs when the response being classified contains insufficient detail, is ambiguous or is vague, or
  • the response is contradictory, for example, both the yes and no tick boxes have been ticked, or
  • the response is clear and seemingly within the scope of the classification, but can not be coded because no suitable option (particularly other residual category options such as 'not elsewhere classified' or 'not further defined') exists in the classification or codefile.

Response outside scope

This category is used for responses that are positively identified (that is, the meaning and the intent are clear) but which clearly fall outside the scope of the classification/topic as defined in the standard.

Not stated

This category is only used where a respondent has not given any response to the question asked, that is, it is solely for non-response.


Australian Bureau of Statistic - ABS survey of domestic energy and water use 2004$File/46184_oct%202004.pdf

Ministry for the Environment - Warm Homes Technical Report: Home Heating Methods and Fuels in New Zealand - 2005

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