Germany's renewable energies levy, which is slapped on market prices for electricity, will have to be increased by 47 percent in 2013, according to calculations released by national grid operators Amprion, 50Hertz, Tennet and TransnetBW.

Additional costs for green power would rise from 3.6 cents per kilowatt-hour this year to 5.27 cents next year, the grid operators said Monday. The four utilities attributed the rise to the boom in solar energy and mounting construction costs.

Under Germany's renewable energies law (EEG), investors in green electricity production enjoy generous state subsidies for up to 20 years, as part of a government effort to boost renewable sources of energy from the current 25 percent to 40 percent within the next decade.

However, the energy strategy has led to rising energy bills in Germany, as subsidies are financed through a special levy. The rise in 2013 is expected to increase energy costs for a three-person household by about 60 euros ($77.4) for the year.

Germany's environment minister Peter Altmaier has already said the country must overhaul the tax and financing expansion of renewable energies to keep costs in check.

uhe/sej (AP, Reuters, dpa)