Production and consumption of energy, energy account

Energy carriers
Sources of energy are called energy bearers. The units used to measure energy bearers are consistent with those normally used in the primary statistics. Coal, coke, crude oil and petroleum products are measured in tonnes, natural gas in standard cubic metres (Sm³), fuel wood, black liquor and waste and other gases in tonnes of oil equivalents (toe) and electric power and district heating in GWh. The energy bearers included in the energy statistics are specified below:

Coal : Anthracite, hard coal and brown coal
Coke : Coal coke and petrol coke
Biofuel : Fuel wood, pellets, briquettes, wood waste, wood chippings, sawdust, shavings, bark, black liquor, biodiesels, bioethanol and charcoal
Garbage/waste : Different types of garbage/waste
Crude oil : Crude oil
Petrol : Naphtha, auto petrol, extraction petrol and aviation fuel
Kerosene : Kerosene type jet fuel, heating kerosene and other kerosene
Middle distillates : Auto diesel, marine gas oil, light heating oils and heavy distillate
Heavy oil : Heavy fuel oils
Waste oil : Waste oil, paint and varnish
Liquefied gases : LPG (propane and butane) and NGL (propane, butane and ethane)
Natural gas : Natural gas in gaseous form and LNG (liquefied natural gas)
Other gases : Refinery gas, fuel gas, methane and CO gas
Electricity : Priority and non-priority power
District heating : Hot water and steam distributed via a district-heating network

Energy content, density and fuel efficiency

¹ The theoretical energy content of a particular energy commodity may vary. The figures therefore indicate mean values.

² Sm ³ = standard cubic metre (15 °C og 1 atmospheric pressure). Net Calorific Value (NCV).

Source: Energy statistics, Statistic Norway, Norwegian Petroleum Industry Association (NP), Norwegian Association of Energy Users and Suppliers, Norwegian Building Research Institute.

Energy units

1 Mtoe = 1 million tonnes (crude) oil equivalents
1 Mbarrels = 1 million barrels crude oil (1 barrel = 0.159 m3)
1 MSm3 o.e. oil = 1 million Sm3 oil
1 MSm3 o.e. gas = 1 billion Sm3 natural gas
1 quad = 1015 Btu (British thermal units)
1 joule (J) = 1 watt x 1 second
Source: Energy statistics, Statistics Norway and Norwegian Petroleum Directorate.

Commonly used prefixes

Production
In the energy sources balance sheet/energy balance sheet, energy production is divided into primary and derived energy bearers. Primary energy bearers include those that are produced without the input of other energy bearing raw materials. The primary energy bearers are coal, fuel wood, crude oil, naphtha, NGL and natural gas. The production of derived energy bearers includes the production of energy bearers in which other energy bearers are used as input, for example, petroleum products manufactured from crude oil in oil refineries or district heating produced through the combustion of waste.

Electricity is treated as primary production in the energy accounts and as derived production in the energy sources balance sheet. The opposite is true of fuel wood. The production of derived energy bearers outside the conversion sectors, for example the production of fuel wood and fuel gas is included in the energy accounts under "other supply". The energy accounts define the sectors that produce primary energy bearers as "extraction sectors" and those that produce derived energy bearers as "conversion sectors". Together, the extraction and conversion sectors are referred to as "energy sectors". The extraction sectors include coal mining and the production of crude oil, natural gas and hydroelectric power. The conversion sectors include oil refineries, thermal power stations, district heating plants and dual-purpose power stations.

Input of intermediate goods In the energy sources balance sheet, energy converted (item 8) represents the volume of energy bearers used as input in the production of derived energy bearers. This item includes inter alia the crude oil that goes to the refineries. The energy sector consumption not used to produce other energy bearers, but used for heating, etc, is entered under consumption by the energy sectors (item 9). In the energy accounts, all input, including input to conversion and input to heating, are entered under "energy sector inputs".

Raw materials
The term "raw material" refers to energy bearers that are not used for energy. This mainly comprises input of petroleum products used to manufacture chemical raw materials. For coal and coke, it is difficult to distinguish between raw material consumption and energy consumption. Accordingly, both the energy accounts and the energy sources balance sheet consider all industrial consumption of coal and coke as energy consumption. Raw material consumption of other energy bearers are separated in the energy sources balance sheet (item 10), but distributed by industry and fuel consumption in the energy accounts.

Consumption outside energy sectors
The consumption outside the energy sectors, net domestic consumption in the energy sources balance sheet (item 13), of coal, fuel wood, electricity and district heating is the same in both systems. There is a deviation in the consumption of LPG because the consumption of raw materials is included in the energy accounts. The consumption of gasoline, kerosene, middle distillates and heavy oil deviates because of different ways of treating international shipping, aviation and raw materials. The consumption of coal for the production of CO gas is included in energy converted in the energy sources balance sheet, while it is included in consumption outside the energy sectors in the energy accounts.

Transportation
The energy sources balance sheet has a separate item for energy consumed for transportation purposes (item 15). This means that the transport sector/item includes not only energy consumed by transport companies, but also consumption for transport purposes in other enterprises, including industries and households. The energy accounts place the consumption of all energy under the relevant consumer sector, regardless of whether the consumption refers to transportation, heating or processing. This leads to different ways of recording the transport oil, gasoline, kerosene type jet fuel, auto diesel, marine gas oil and heavy fuel oil. Aviation is treated differently in the two systems, as Norwegian transport companies' acquisitions abroad are included and purchases by foreign transport companies in Norway are deducted from the energy accounts. Military consumption of kerosene type jet fuel is entered under public administration, not under aviation.

International shipping
Regardless of a vessel's nationality, energy bearers supplied by Norwegian ports to vessels in international shipping are categorised as bunkering in the energy sources balance sheet and not included in the total consumption (item 4). International shipping is considered a separate transport sector in the energy accounts, so consumption is recorded under the item "consumption outside the energy sectors". The energy accounts also include Norwegian vessels' consumption of energy abroad. International shipping both buys and uses most of its fuel abroad. Correspondingly, the energy sources that foreign vessels buy directly in Norway are deducted.

Common energy unit for the energy accounts and the energy sources balance sheet
Both the energy accounts and the energy sources balance sheet are presented in two different types of units: in physical units (tonnes, GWh etc) and in a common energy unit, petajoule (PJ). Presented in PJ, the energy sources balance sheet is referred to as the energy balance sheet. The figures in PJ are calculated on basis of the figures measured in physical units, using factors for the theoretical energy content for each commodity. From 2006, some new tables are published, with all commodities presented in GWh.

The layout of the energy balance sheet differs from the layout of the energy sources balance sheet on several points: In the energy balance sheet, there is a column showing the total for all the energy commodities. There is also a column for waterfall energy, showing the primary stage for electricity produced by the hydroelectric power plants.

Item 1.2. "Production of derived energy bearers" has been moved to avoid double entries in the total column on the supply side.

Item 7. "Net domestic supply" shows the consumption of energy before the transformation processes begin. This level of measurement includes the production of primary energy bearers adjusted for imports, exports/bunkering and changes in stock. For example, crude oil is included in this calculation. To avoid double entries, the consumption of individual petroleum products derived from crude oil has not been included.

Item 13. "Net domestic consumption" shows the theoretical energy content of bearers delivered for end use - the energy supply. Thus the values at this level of measurement have a degree of efficiency utilisation of 100 per cent for all energy bearers on end consumption. Of course, in practice, this would be impossible. The loss of efficiency that occurs when the energy bearers are used to produce heat, run motors, etc is not taken into account. Take a furnace, for example: Some of the theoretical energy content will not reach the consumer as heat, because a furnace is not 100 per cent efficient. Chapter 6 in NOS Energy Statistics 2000 (see link below) contains a table showing the consumption of utilised energy. The consumption is calculated on the basis of figures from the energy balance, and the estimated thermal efficiency coefficient of different energy sources (see separate table).

In international statistics, the expression "Total primary energy supply" (TPES) is used. TPES = Total primary production + imports - exports - bunkering - changes in stocks.

The structure of the energy accounts in PJ differs only slightly from the energy accounts expressed in physical units.

The industrial classification used is an aggregated and somewhat modified version of the EU standard NACE. The figures are even more aggregated in the published tables. In 2009, from and including the reference year 2008, the industry classification in the energy accounts / balances was changed according to the new NACE standard SN2007.

Name: Production and consumption of energy, energy account
Topic: Energy and manufacturing

Division for Energy, Environmental and Transport Statistics

Only national figures are published. The figures for consumption of fossil fuels and bio fuel are also distributed by municipality for use as a basis for the calculation of emissions to air.

Annual Energy accounts and energy sources balance sheet: Publishing in the autumn of figures for year t-2, preliminary figures for year t-1 (year t is the publishing year)

Energy sources balance sheet: Publishing in the spring of "very preliminary figures" for year t-1.

The energy sources balance sheet is reported annually to the IEA/OECD, Eurostat and the UN.

The energy accounts for the most detailed sector classification level are available in Excel files for each year back to 1976, the energy balances on the detailed level are available back to 1990. Micro data for the single units (enterprises) from the statistics on energy use in the manufacturing sector are stored on Unix files. The excel files may contain confidential data and can therefore not be published.

The statistics have been published annually since 1976. In 1993, Statistics Norway introduced a new industrial standard, based on the EU standard NACE. The energy accounts and the energy sources balance sheet use an aggregated and somewhat modified version of this. It is somewhat more aggregated, partly due to that information about energy consumption not is available for all the NACE sectors. The nomenclature in the energy account /balances was adapted to the nomenclature in the national accounts (for 1995), but there are some discrepancies, partly because the nomenclature in the national accounts has changed since then. For the years 1990-92 the energy accounts and the energy sources balance sheet have adapted the old industrial codes to this new classification. In a revision of the sector classification of the Central Register of Establishments and Enterprises, some enterprises were reclassified and placed in other sectors from 1993. This means that the figures for energy consumption in some sectors are not fully comparable for the years prior to and after 1993. Prior to 1990, various sources were to some extent used in the energy accounts and the energy sources balance sheet. From 1990, however, the data are consistent. The only differences between the energy accounts and the energy sources balance sheet now are the principles and definitions.

The statistics are used by public and private institutions that work with different types of energy questions and analyses. Internally in Statistics Norway, the Division for Energy and Environmental Statistics, the Research Department and the Division for National Accounts are important users. The energy accounts are an important part of the data material that is used as a basis for the calculation of emissions to air. Statistics Norway calculates the emissions in co-operation with the Norwegian Environment Agency. The Research Department uses the statistics for analyses and prognoses, while the Division for National Accounts uses it in the NOREEA (environmental accounts). Schools, the media and various organisations are other users of the statistics. Figures for energy consumption by region are used in local energy and climate plans.

Because the energy sources balance sheet and the energy accounts are based on different principles and definitions, some of the figures differ. It should therefore be considered which of the two presentations will be the most relevant. One should, however, avoid mixing figures from the two accounts.

The energy sources balance sheet is based on international standards for how to set up an energy balance. However, even if an energy balance follows certain principles, there are some minor differences in how different countries and organizations such as IEA set up the energy balance. Due to this, Norway's energy balance cannot directly be compared to other countries' or organizations' energy balance. An energy balance monitors the flow of energy in the country, irrespective of the nationality of the users. The balance sheet has a separate item for energy used for non-energy purposes (energy not used as fuel, but as input in industrial production). Regardless of this, all industrial consumption of coal and coke is considered as energy consumption because it is difficult to distinguish between raw material consumption and energy consumption. All energy used for transport purposes is also placed in a separate item in the balance, irrespective of user group.

The energy account is based on the definitions in the national accounts, and follows the residence principle while the energy balance follows the territorial principle. Energy used by Norwegian transport services and tourists abroad is included, while energy consumed by foreign transport sectors and tourists in Norway is excluded. Energy used for non-energy purposes is distributed by user group together with other energy consumption. Energy used for transport purposes is placed in the user group that actually uses it.

Not relevant

The preliminary energy balance is published in the spring. This is a rough balance without any detailed sector division. The consumption of oil products is to a large extent based on sales figures for the different products. As the sector distribution in the statistics on deliveries of petroleum products is not satisfactory, the figures for consumption by sector are uncertain. However, the total figures are reliable.

Preliminary figures for emission to air are presented at the same time as the preliminary energy balance, and are partly based on the same figures. A more detailed preliminary version of the energy accounts and energy sources balance sheet and final figures for the previous year are produced and published in the autumn.

The energy accounts should in principle be comparable to the national accounts because the sector classification and principles/definitions are approximately similar. However, there have been some discrepancies because different sources are used for quantity figures in the energy accounts and value figures in the national accounts.

Coherence between the energy balance and the monthly and annual electricity statistics
The annual and monthly electricity statistics is the data source for production and consumption of electricity in the energy balance / accounts. When finally and preliminary energy account / balance for year t -1 and t-2 respectively, (year t is the publishing year) is prepared during the autumn, figures from the annual electricity statistics are used in the final figures while figures from monthly statistics are used in the preliminary figures. The annual electricity statistics is not published before about 15 months after the reference year, and is due to this not available for the preliminary energy balance for year t-1 in the autumn. Figures in the annual electricity statistics and the energy balance (final figures) should in principle be the same, but there are some exceptions. Production plants, or plants that generates electricity for their own use mainly, should be included in the annual electricity statistics, but it can take some time before they are included, and are sometimes not included for all years. In these cases, we have in the energy balance added their production and consumption to the other figures in the annual electricity statistics.

There are also some differences in the contents in certain concepts. The net consumption of electricity is defined different in the energy balance and the electricity statistics. In the annual electricity statistics, this is defined as total production + imports - exports - consumption in power stations - pump consumption - losses and statistical differences. In the energy balance, consumption in other energy producing industries, such as district heating plants, oil and gas extraction, oil refineries and coal extraction are also excluded from the net domestic consumption. This implies that the net domestic consumption of electricity in the energy balance becomes lower than in the annual electricity statistics.

Regarding electricity consumption by sector and industry, the annual electricity statistics is the main source in the energy balance. An exception is manufacturing industries, where figures from a separate survey on energy consumption in manufacturing industries are the source. Usually, this survey shows a higher consumption for manufacturing industries than the electricity statistics does. To calibrate total electricity consumption in the energy balance and the electricity statistics, we have to reduce the consumption in other sectors, usually the service sectors. For households, the sum of consumption in households and cottages/holiday houses from the annual electricity statistics is used directly as consumption in households in the energy balance.

The Statistics Act §§ 2-1, 2-2 and 2-3. The statistics are mainly based on data from other statistics

Not relevant

The statistics cover the consumption and supply of all energy commodities in Norway (oil, electricity, gas, coal, coke, district heating, biofuels etc). Energy sources that are of very little importance for the Norwegian energy supply, for instance solar energy and geothermal energy, are not included. On the consumption side, the statistics cover energy consumption in all sectors (energy sectors, manufacturing industries, construction, private and public services, primary sectors, households). The statistics include about 130 different sectors, but the figures are published on a more aggregated level

The sources are available basic statistics, partly from Statistics Norway's own statistics, partly from other institutions. Relatively few figures are collected only for the purpose of being used in the energy accounts and the energy sources balance sheet. Internal statistics that are used include statistics on energy use in the manufacturing sector (a separate survey from 1998), electricity statistics, statistics on delivery of petroleum products, refinery statistics, domestic use of natural gas statistics, district heating statistics, external trade statistics and the national accounts statistics. For some sectors, projections of figures from previous energy consumption surveys are used. Data from the Norwegian Petroleum Directorate on the production of crude oil and natural gas are among the many external data that are used. The various statistics that are used as data sources do not always provide all the details needed in the energy accounts and balances, and therefore, some figures are based on estimates.

Production
The production figures for coal, petroleum products and refinery gas are taken from internal sources in Statistics Norway, while those for crude oil and natural gas are taken from the Norwegian Petroleum Directorate. The production figure for fuel wood is calculated as the sum of consumption of fuel wood plus exports minus imports. The production figures for blast furnace gas and fuel gas are taken from two major Norwegian companies. The production figures for electricity are taken from Statistics Norway’s annual electricity statistics, while figures for district heating are taken from Statistics Norway's district heating statistics.

Imports, exports, stock changes, intermediate goods and losses
The import and export figures are extracted from Statistics Norway's external trade statistics. The changes in stock are mainly taken from Statistics Norway's statistics on stocks, which include stocks at refineries, crude oil terminals and oil fields. Changes in coal and coke stocks include changes in the stocks of Store Norske Spitsbergen Kulkompani and major consumers. The input of intermediate goods (input in energy producing industries) are based on figures from the monthly refinery statistics, figures from the Norwegian Petroleum Directorate, annual or monthly (for preliminary figures) electricity statistics, the district heating statistics and refinery statistics and the Norwegian Petroleum Directorate. Figures on losses are derived from the annual electricity Statistics and the district heating statistics.

Coal, coke and energy used as raw materials
Coal and coke are mainly used as raw materials in manufacturing industries in Norway. The figures for industrial consumption of coal and coke are taken from a separate survey for the 40-50 largest enterprises in Norway. Figures for other energy sources used as raw materials, as LPG, is also collected in this survey. The sample cover the main users of coal and coke and other energy used as raw materials in Norway. The figures on agricultural and private household consumption of coal and coke are estimates based on information provided by Forenede Kulimportører A/S, Scancem A/S and Store Norske Spitsbergen Kulkompani A/S.

Manufacturing industries
Figures for energy consumption in manufacturing industries, except energy used as raw materials, are from 1998 taken from a separate statistics of energy use in the manufacturing sector. Prior to this, the source was manufacturing statistics, which also included figures for energy consumption.

Fuel wood in households

Statistics on use of wood in households is based on figures on the amount of wood burned from the annual survey on consumer expenditure for the years before 2005. For the years after 2005 the figures are based on responses to questions relating to wood-burning in Statistics Norway’s Travel and Holiday Survey. The survey quarterly gathers data that cover the preceding twelve months. The figure used in the emission calculations is the average of 3 to 5 quarterly surveys. More than 1 000 persons are interviewed by telephone every quarter. The response rate is around 60 per cent.

Theoretical energy content is calculated by multiplying the consumption of wood by the factor for energy content. (See table under Definitions.) Energy generated is calculated by multiplying the theoretical energy content by rates of energy efficiencies for different ovens technologies.

Energy efficiencies for different oven technologies. Per cent

Petroleum products
The consumption figures for petroleum products are based on statistics on deliveries of petroleum products. The breakdown by industrial group comes from the statistics on energy use in the manufacturing sector. The Norwegian Environment Agency is the source for consumption of landfill gas, while the consumption of waste oil, paint and varnish etc is based on figures from NORSAS until 1999. From 2000, these data are included in the statistics on energy use in the manufacturing sector. For other industries, data are collected by the division for Energy and Environmental Statistics.

Electricity
The distribution of electricity consumption between the main groups is taken from annual electricity Statistics. The statistics are based on data submitted by all companies that produce and distribute electricity. Since this sector usually categorizes its own statistics on the basis of various types of tariffs, it is often difficult to accommodate data to the categorization used in the energy sources balance sheet. Industrial energy consumption figures are taken from the statistics on energy use in the manufacturing sector.

District heating
The distribution of district heating consumption between consumer groups is taken from the district heating statistics. To achieve a more detailed distribution, statistics from the Directorate of Public Construction and Property have been used.

Natural gas
The consumption of natural gas by industry outside the manufacturing industries is reported by the distributors of natural gas in Norway.

Statistical errors
Statistical errors represent deviations between the consumption and supply of energy bearers. In principle, the supply of energy (production + imports) should correspond to exports and consumption of energy. However, there are many reasons for deviations; erroneous registration, conversion from other units of measurement, the use of different statistical sources, etc. Statistical errors for crude oil and natural gas are sometimes very high. This could be due to inaccuracy in the figures for production or exports, or these figures might not be consistent. Even if the statistical errors are relatively low compared to total production, they can be high compared to the total domestic energy consumption.

Other sectors
Energy consumption in fish farms, distribution of water, IT activities and ocean transport are calculated on the basis of figures from the national accounts and prices from the electricity statistics, the Norwegian Petroleum Industry Association (NP) and Shell.

The energy accounts and the energy sources balance sheet cover the total supply and consumption of energy in Norway. The statistics that are used as sources are to a large extent statistics that cover the total population. The statistics on energy use in the manufacturing sector do not cover all enterprises, but the sample covers more than 90 per cent of the total energy consumption in the manufacturing industries. For other units, the energy consumption is estimated.

Available data are used as much as possible, partly with small adjustments for calibrating the total accounts. For oil products, the energy accounts and energy sources balance sheet define the domestic consumption as identical to registered sales exclusive of consumption by international shipping and aviation. For sectors where reliable information is not available, the consumption is partly calculated as a residual, partly on previous surveys or data that may indicate the consumption (such as employment, the number of private cars etc). The statistics used as source are mainly annual, except the statistics on deliveries of petroleum products, the refinery statistics and the preliminary electricity statistics, which are monthly. From 2006, data on deliveries of biofuels are collected by survey.

All the necessary data are not available at the time when the preliminary energy accounts and energy balance sheet are produced. As a result, some temporary calculations and estimates have to be used. These are revised when the final energy sources balance sheet is produced.

When the energy accounts and energy sources balance sheet are published, data for total supplied energy consumption are presented. In addition, the data from the energy balance sheet are presented as utilised energy. The figures for utilised energy take into account that it is not possible to fully utilise the theoretical energy content of any energy bearer (except electricity), due to heating equipment, car engines etc not being completely efficient. Utilised energy is calculated on the basis of the thermal efficiency coefficients of the different energy sources and consumer groups.

Both the energy accounts and the energy balance sheet are presented in two types of units: in physical units (tonnes, GWh etc) and in a common energy unit, petajoule (PJ) and GWh respectively. The figures in PJ and GWh are calculated on the basis of the figures measured in physical units, and with factors for the theoretical energy contents in the different energy products. When presented in PJ or GWh, the energy sources balance sheet is referred to as energy balance sheet.

Not relevant

The general rule for publication is that data cannot be released unless they contain information from at least three or more participants (i.e. industrial enterprises etc). This rule can be waived if permission from the parties involved is granted.

The energy accounts and the energy sources balance sheet have been produced since 1976. The sector classification was changed in 1993, and a rough adaptation to this new nomenclature was made for 1990-92. The sector codes for some enterprises were changed in 1993. Changes in the calculation methods over the years mean that the time series for consumption are not fully comparable for some sectors.

This depends on the quality of the source statistics. In the statistics on energy use in the manufacturing sector, errors may occur due to misunderstandings, or because those who fill in the questionnaire do not have enough knowledge about the actual energy consumption or how to classify the consumption. Use of estimates instead of actual figures represents another source of uncertainty. Errors may also occur during data transfer and revision. The statistics on deliveries of petroleum products by user group is uncertain because the oil companies do not know exactly where the end consumption takes place, for instance when oil products are delivered to filling stations that distribute the products to other customers. Furthermore, high uncertainty is connected to consumption figures based on projections of previous surveys, for instance consumption in many of the service sectors.

The preliminary figures for electricity distributed by consumer groups outside the manufacturing industries are quite uncertain because the annual electricity statistics are not available when the preliminary energy accounts/energy sources balance sheet are produced.

The methods used in the energy accounts were evaluated in 2005. This work revealed several defects and weak points in the energy statistics and resulted in a list of possible new data sources and methods. Hopefully, making use of these new sources and methods will improve the quality of the accounts. A problem, however, is how to recalculate and achieve consistent time series.

Statistical errors represent deviations between the consumption and supply of the energy bearers.

The data sources are basic statistics which already are weighted and corrected for non-response errors.

Uncertainty in energy consumption in manufacturing industries

Uncertainty concerning energy use in manufacturing industries is connected to the fact that the results are based on data from only a part of the population/enterprises. This uncertainty is, however, small, as the enterprises in the sample represent 90 per cent of the energy use in mining and manufacturing.

Sources of uncertainties - wood consumption in households

There are several elements of uncertainty related to the data, including sample uncertainty and uncertainty in conversion factors

Final figures for 2011 are based on three quarterly surveys. Each survey asks about wood consumption for the last twelve months. The three surveys are weighted equally.

An uncertainty analysis was conducted in 2011. The coefficient of variation of the estimated total consumption in Norway is a little less than 3 percent. The table below shows how the uncertainty in the national numbers increases when the number of studies decreases:

In 2011 the total wood consumption in Norwegian households is estimated to be 1.3 (± 0,1) million tonnes. In addition, 210 000 (± 28 000) tonnes of wood were burnt in holiday homes. The consumption of wood in households produced energy equivalent to 3.79 (± 0.3) TWh in 2011. The numbers for the municipalities are more uncertain than the national total .This is because the numbers are based on fewer respondents.

The statistics does not give the total number of furnaces in Norway, but the number households that uses firewood. If a household has more than one fireplace, they have provided information on the technology most used

Measuring problems or inconsistency in methods for collecting or calculating figures for production, exports and imports specially for oil, gas and oil products can imply statistical differences for these energy commodities.

Not relevant