# ECOMET price units

**EPU (ECOMET Product Unit)**

To compute the price of products, we need to have a quantitative measure of the information given by the meteorological products.

For Numerical Weather prediction model, the output product is usually offered as computer files. It is not possible to assign a value directly proportional to the amount of information (expressed, for instance, in Bytes, or in Grid point value), since this amount is very dependant on the resolution of the grid, and it is easy, through interpolation techniques, to change this resolution without modifying the meteorological value of the product.

For meteorological maps as well, since the area, the number of fields, the definition may vary, it is useful to adopt a common way of evaluating the amount of meteorological information

contained in the map.

For these reasons, ECOMET has proposed to express the value of the meteorological products

such as NWP model output and meteorological maps with a common conventional unit which is called "ECOMET Product Unit" (EPU). This method allows to compute prices for heterogeneous sets of products.

In harmony with the ECMWF practice of price calculation of NWP products, the total number of EPU for one global NWP product (one model run, one time-step, one element, full spatial resolution, global area coverage) is set to 20.

This number is not related to the spatial resolution or other features of the NWP products.

Basic price per EPU

The number of EPUs per NWP field (NEi) will result from the formula:

**NEi = 20 * Ai**

where Ai is the area factor defined as the ratio between the area of the provided NWP field and the area of the globe.

The price of a licence (LP) for a variety of NWP products will consequently result from the formula:

**LP = VP * Σ ( NEi * FEi )**

where

- VP is the discount factor for the total amount of NWP products according to the ECOMET volume discount scheme
- FEi is the licence fee per EPU for the respective NWP item within the ECOMET Catalogue

**ECOMET Radar Unit (ERU)**

Analogue to the EPU for NWP products an ECOMET Radar Unit (ERU) is defined, which is one frame of either a single site radar observation or of a composite image.

The ERU is designed for the calculation of the volume discount. The price of a single site radar is listed in the Price List.