Heating and hot water prices in Bulgaria will increase by at least 10-15 per cent from July 1 2010, while electricity tariffs might remain unchanged but only at the expense of power distributors, according to energy watchdog chairman Angel Semerdjiev.The possible hike in heating bills by about 15 per cent does not include the increase in gas prices, which should be approved by the State Energy and Water Regulatory Commission (SEWRC) by July 1.This means that the increase in heating prices will be much steeper.At the same time, the regulator is trying to fend off a high power hike from July 1 after it estimated in a report that bills should increase by between five and seven per cent for end-users.Semerdjiev said that power distributors had accumulated "reserves" that could enable the SEWRC to retain electricity prices. He said that the regulator is expecting the results from the audit being carried out on the distributors.ESO, the electricity system operator of Bulgaria's state-run power utility NEK, cautioned that a drastic hike in electricity prices could jeopardise Bulgaria's energy security.On the other hand, distributors - the Czech Republic's CEZ, Germany's E.ON and Austria's EVN - protested that they would incur losses from SEWRC's price rise proposal but would be devastated if prices are kept intact.