Homeowners need not shower under a dribble to comply with new electricity conservation measures, say the Greens.

Many people reacted angrily last week to reports the Government was planning to limit the allowable flow from shower heads to as little as six litres a minute - half the average shower strength now.

But Green Party co-leader Jeanette Fitzsimons said the six-litre limit was a last-ditch option for new home builders who did not want to do anything else to make their hot water energy-efficient.

The Department of Building and Housing is consulting on water-heating rules to apply to new homes from February. Under the new rules, an online calculator (www.dbh.govt.nz/energy-efficiency) will tell builders and plumbers whether they have done enough to make a hot-water system energy-efficient.

But even the most wasteful systems will be able to automatically comply, by adding a low-flow shower head that releases six litres of water a minute (for homes bigger than 150sq m) or 7.5 litres a minute (for smaller homes).

The Government's consultation document says the limits are a "simple means of compliance for those who do not wish to use the online calculator".

Ms Fitzsimons said most people would choose showers releasing at least nine litres a minute, and find other ways to comply with the rules.

Other options include:

* Installing a good quality, well-insulated hot-water cylinder.
* Installing a hot-water heat pump;
* Using a wood-fired wetback water heater.
* Designing your home so there is a short distance between the cylinder and the taps.
* Installing a solar-ready cylinder that allows a solar panel connection in the future.

Homes with instant gas water heating qualify for a shower flow of at least 7.5 litres a minute.

Ms Fitzsimons said households could save $300 a year under the new rules.

The Greens say most New Zealand homes already have shower heads that would be considered "low flow" under the new rules.

Only people building new homes with high-pressure water systems will be affected by the changes.

The rules do not apply to people renovating in an existing home. The only limit on them is that the replacement system cannot be less efficient than the original.