THE Climate Change Minister, Greg Combet, is looking for new ways to slow the runaway demand for rooftop solar systems that has put pressure on electricity prices and made it harder to sell the government's proposed carbon price.

Mr Combet is understood to be very concerned at the huge growth in rooftop solar, fuelled by generous state and federal subsidies, and is considering options to slow demand, including requiring households to buy bigger and more expensive systems to be eligible for a reduced federal government subsidy.

State governments have become increasingly alarmed at the pressure on electricity prices from the federal subsidy, which flows straight through to power bills because it requires electricity retailers to buy ''solar credits'' awarded for renewable power generated on household roofs.

And federal Labor is worried the scheme is forcing increases in electricity bills just as it is struggling to sell its new carbon tax.

In December, when almost half of a 6 per cent increase in a draft determination for increases in Queensland electricity prices was caused by the federal renewable energy target, the Queensland Premier, Anna Bligh, wrote to the Prime Minister, Julia Gillard, asking her to review the federal scheme.