The RWE group, the biggest Czech gas supplier, said it would raise prices for households by 2.9 percent as of April. Pražská plynárenská, supplying gas in the Prague area, is going to raise prices by 2 percent on average as of April. Vácha said the reason is the gradual increase in prices of crude oil and oil derivates as well as the strengthening of the dollar to the Czech crown. The last time E.ON raised prices was Oct 1, 2008.