The Government has been paying lip service to the subjects of climate change and environmental sustainability for a long while. Now it has bared some teeth, first introducing legislation to require motor fuel companies to sell some biofuel, followed closely by an "energy strategy" that proposes a qualified ban on the building of fossil-fuelled electric power stations for 10 years.

The ban is not absolute; a new oil- or coal-fired station may be permitted if the Electricity Commission thinks it necessary to maintain the security of the country's power supply. But for ordinary growth in base-load capacity the power companies will need to look to new water, wind, tidal or other renewable resources.

The edict expressly applies to the three state-owned generating companies, Meridian, Genesis and Mighty River, and probably to the independent Contact as well. In fact Contact is the first to respond to the strategy, announcing plans last week to build a gigantic wind farm on the Waikato coast.

If permitted, the 218 propellers will stand 65m tall, higher than the Auckland Harbour Bridge, over an area larger than Great Barrier Island. Contact says none of the turbines will be seen from the road or from any property except the farms that will receive income from this use of their land. Nevertheless, the scale of the proposal is an early warning that alternatives to fossil fuels will be no kinder to the landscape.

As part of the Government's strategy the Electricity Commission will review its requirements for security of supply, set when the commission was created after two years of low rainfall and high prices. Presumably the reserve generating capacity will be set lower to encourage more renewable generation but we shall see; political safety was the Government's priority at that time and there is no reason to believe it would be braver now. Sustainable energy and secure energy are "not mutually exclusive goals", the Prime Minister maintains. But the fact is oil- and gas-fired stations are the country's security against low hydro levels and it's hard to see that any weather-dependent power plant could pick up the slack in a dry season.

Much may depend on a companion plan announced last week to reduce electricity consumption. The "energy efficiency strategy", which seems to be in the care of the Green Party, envisages mandatory insulation of rental homes by landlords, interest-free loan incentives for insulating and incentives to retire poorly functioning or superfluous appliances. The Greens cited the beer fridge.

Reducing transport emissions will be harder. The Government has set itself a target of halving them by 2040, hopefully by perfecting electric cars. In the meantime, besides the biofuel sales obligation it may put more teeth into vehicle efficiency standards. Beyond that, it vaguely intends to encourage more use of public transport, cycling and walking.

It has bared perhaps as much teeth as it dares for the time being. The moratorium on fossil fuel generation, mandatory biofuel sales and the insulation obligation are fairly draconian impositions on the businesses concerned and will interfere with economic efficiency.

But with the Maui gas field expiring and electricity use rapidly rising in the computer age, new generating capacity is overdue. Power companies have had investment on hold while they waited to see the Government's resolve. The fossil fuel moratorium was the intended signal and Contact's Waikato announcement was the return message. Big change is in the wind.