In a report commissioned by the Green party, expert Gunnar Harms has warned that energy companies may be over-charging private households by as much as three billion euros. Harms is a member of the opposition Green party in the federal parliament. He claimed that recent increases in electricity prices had not been justified. He argued in his report that in 2011 suppliers had paid 20 percent less on the wholesale power market. He also claimed that the phase-out of nuclear energy has not led to the explosion of prices that some analysts had expected. \"We\'ve seen over the past five years that whenever there\'s a market price hike for electricity, it\'s immediately passed on to private households,\" Harms’ study says. \"But when there\'s a reduction in market prices, consumers do not tend to benefit at all.\" Private versus industrial customers The survey claims that while private consumers have been receiving higher electricity bills in recent years, prices for large industrial clients have dropped by 20 percent since 2008. Harms says such a policy is unfair and gives energy-intensive industries an unnecessarily good deal. A spokesman for Germany\'s Association of Energy-Intensive Industries (EID), Martin Kneer, said in a statement on Friday that industry was not to blame for higher electricity prices in private households. \"Higher prices are not the result of us getting a better deal, but because of the unfettered growth in the renewables sector,\" Kneer said in reference to the massive state subsidies involved. Federal Environment Minister Peter Altmaier said he expected energy prices for households to rise by a further five percent later this year due to development costs for solar energy.