But in the ACT Legislative Assembly yesterday, Environment and Sustainable Development Minister Simon Corbell accused the opposition of ''extraordinary ignorance'' and a failure to understand the scheme, which will overhaul Canberra's electricity sector.

The legislation, which the government says will save 70,000 households up to $300 each on their annual electricity bills by 2015, was passed by the Assembly yesterday with support from the ACT Greens.

The scheme will force electricity retailers to offer to replace their customers' old appliances, while power companies will have to subsidise or pay for energy efficiency upgrades to homes.

Opposition Leader Zed Seselja claimed household costs would actually increase as a result of the legislation and that the main recipients of the scheme would be large companies. ''Most Canberra families will receive no benefit under this scheme … '' Mr Seselja said.

''When a large supermarket decides it wants to save money by upgrading its heating and cooling system, it's Canberra families that will have to foot the bill to subsidise the company's costs.

''What we are talking about fundamentally is big business welfare.''

Mr Corbell ridiculed the Opposition Leader's ''outrageous, stupid and ill-informed claim'', by saying the scheme was not even available to big business and only later would it be expanded to include small and medium businesses.

He said 25 per cent of households taking part in the scheme would be low-income earners.

ACT Greens MLA Shane Rattenbury welcomed the scheme and said it would deliver benefits for both low-income households and renters.

''There are currently multiple barriers to the uptake of cost-effective energy measures and schemes such as this can go a long way towards overcoming these barriers,'' he said.

The government's regulatory impact statement shows the scheme will save households taking part $2140 over the life of the upgrades and deliver $40 million to the ACT economy.