The BEMS package records a data value every 15 minutes for each Item and its associated measurements (for electric power a single Item has potentially 5 measurements: KWH, KVARH, Max Demand, Kilowatts and Load Factor).
These apply to the Project Node (for BEMS ODBC database files).
Each ODBC record requires about 34 bytes on the hard drive of the Project Node (a group of Access Database by default, in a subdirectory at drive:\WebAcces\node\bamdb).
20 tags * 34 bytes/sample * 4 samples/hour * 24 hours/day * 30 days/month = 2 Megabytes in a month.
20 tags * 34 bytes/sample * 4 samples/hour * 24 hours/day * 365 days/year = 23 Megabytes in a year.
The Maximum file size of an Access Database is 2 gigabytes.