The energy system operator (ESO) updates a page with production/consuption 
Mw every 35 seconds. You can find the original data here:
http://www.eso.bg/default.aspx/page-707/en

The values are as follows:
- Nuclear (NPP)
- Condensing Termo (TPP)
- Polygeneration TPP
- Factory TPP
- Hydroelectric (big dams)
- Small Hydroelectric
- Wind
- Photovoltaic
- Bio TPP
- Consumption nationwide

The issue with this page is that there's no historic data. We get only a 
stream with the latest values. This site scrapes that page and structures it. 
The download is scheduled for every 30 seconds, but the original update 
times from ESO are kept. The download began on 21 april 16:00 with rate of 
once per minute. On 23 april it was increased to 30 seconds.

The original data can be downloaded from 
http://opendata.yurukov.net/energy/data/production/eso_production.zip 
It contains an Unix timestamp and the values for all the columns described 
above. This archive contains dataset dumps for each day and is updated at 
midnight GMT. 

With the API one can get summed up data with grouping per hour, day, week, 
month or year. Default is day. You need to specify a begin and an optional 
end date, which defaults to today. The date format follows the php date 
specs. Each raw of the dataset contains the date/time and three columns 
for each of the values in the list above - average Mw for the given time 
period, max and min. 


A second dataset is contained in the ZIP archive. It consists of the cross-
border loads with neighboring countries per hour. The course is:
http://www.eso.bg/default.aspx/cross-border-physical-flows/en
It is being scraped once a day. Negative values mean that power is 
imported in Bulgaria The data is in separate files, because the
granularity is different than the internal production/consumption. In the
API however, three columns (avg,min,max) are added for these fields:
- transfer Turkey
- transfer Greece
- transfer Macedonia
- transfer Serbia
- transfer Romania
Since ESO updates the crossborder loads for the previous day, you won't
get the values for the current day.

Please don't abuse the API. Cache the responses and/or download the full 
data once per day. For questions and feedback, please contact me at 
@yurukov or yurukov@gmail.com.

More opendata on Bulgaria:
http://opendata.yurukov.net/
http://opendata.yurukov.net/vei/en (renewable energy production in 2012)
http://datahub.io/group/bulgaria

Boyan Yurukov