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Frequently Asked Questions

1. What are the methods of calculation of primary energy equivalent? 
2. Why are the some of the data in the questionnaires in gross units and not in net units? 
3. What is the difference between Main Activity and Autoproducer? 
4. Why do you not take the data from the website of the national administrations?
5. What do the IEA and Eurostat do with the annual questionnaires?
6. What types of checks are done on the data?
7. Is a manual available to explain the IEA methodology?
8. What is a PPP?


1. What are the methods of calculation of primary energy equivalent?

There are essentially two methods that can be used to calculate the primary energy equivalent of the above energy sources: the partial substitution method and the physical energy content method. Since these two types of energy balances differ significantly in the treatment of electricity from solar, hydro, wind, etc., the share of renewables in total energy supply will appear to be very different depending on the method used. As a result, when looking at the percentages of various energy sources in total supply, it is important to understand the underlying conventions that were used to calculate the primary energy balances.
The partial substitution method: 
In this method, the primary energy equivalent of the above sources of electricity generation represents the amount of energy that would be necessary to generate an identical amount of electricity in conventional thermal power plants. The primary energy equivalent is calculated using an average generating efficiency of these plants. This method has several shortcomings including the difficulty of choosing an appropriate generating efficiency and the fact that it is not relevant for countries with a high share of hydro electricity. For these reasons, the IEA, as most of the international organisations, has now stopped using this method and adopted the physical energy content method.
The physical energy content method: 
This method uses the physical energy content of the primary energy source as its primary energy equivalent. As a consequence, there is an obvious link between the principles adopted in defining the primary energy forms of energy sources and the primary energy equivalent of these sources. For instance, in the case of nuclear electricity production, as heat is the primary energy form selected by the IEA, the primary energy equivalent is the quantity of heat generated in the reactors. However, as the amount of heat produced is not always known, the IEA estimates the primary energy equivalent from the electricity generation by assuming an efficiency of 33%, which is the average of nuclear power plants in Europe. In the case of hydro, as electricity is the primary energy form selected, the primary energy equivalent is the physical energy content of the electricity generated in the plant, which amounts to assuming an efficiency of 100%.

2. Why are some of the data in the questionnaires in gross units and not in net units?

In the questionnaires, we use gross units since trade with the products is usually collected on a gross unit basis.

3. What is the difference between Main Activity and Autoproducer?

Main Activity supply undertakings generate electricity and/or heat for sale to third parties, as their primary activitywhereas Autoproducer undertakings generate electricity and/or heat, wholly or partly for their own use as an activity which supports their primary activity.

4. Why do you not take the data from the websites of national administrations?

We cannot take the data from your websites since we do not know how much the methodology you use there is consistent with IEA methodology. To ensure this we provide you with the questionnaire.

5. What do the IEA and Eurostat do with the annual questionnaires?

The data are loaded in the annual questionnaire databases and a series of checks are done on the data. Queries are sent back to the countries for any outstanding problems. When the data are "finished", they are published in book form, on CD-ROM and on the internet.

6. What types of checks are done on the data?

The EXCEL file version of the questionnaire does some basic arithmetic and consistency checks. This permits countries to make corrections before actually sending the questionnaires to the IEA and to Eurostat. After the questionnaire arrives in the IEA and Eurostat, the statisticians check again for arithmetic errors, time series discrepancies and consistency within each questionnaire and between questionnaires. Finally, energy balances are run and efficiencies calculated to identify problems either in inputs or outputs to the various transformation processes.

7. Is a manual available to explain the IEA methodology?

Yes, but the Manual is already available in ten languages and can be accessed and downloaded by clicking here. The Manual has been prepared by the IEA and Eurostat.

8. What is a PPP?

The GDP data have been compiled for individual countries at market prices in local currency and annual rates. These data have been scaled up/down to the price levels of 2005 and then converted to US dollars using the yearly average 2005 exchange rates or purchasing power parities (PPPs). Purchasing power parities are the rates of currency conversion that equalise the purchasing power of different currencies. A given sum of money, when converted into different currencies at the PPP rates, buys the same basket of goods and services in all countries. In other words, PPPs are the rates of currency conversion which eliminate the differences in price levels between different countries. The PPPs selected to convert the GDP from national currencies to US dollars were aggregated using the Geary-Khamis (GK) method and rebased on the United States. For a more detailed description of the methodology please see Purchasing Power Parities and Real Expenditures, GK Results, Volume II, 1990, OECD 1993.

E-mail: stats@iea.org

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