Queenslanders don't have to install rainwater tanks and energy efficient hot water systems in new homes under new state laws.

The old laws forced homebuilders to install gas, solar or heat pump hot water systems.

Housing Minister Tim Mander claims the change, which came into effect earlier this month, will reduce the cost of building a new home by $5000.

"Under the old laws people had no choice but to install a rainwater tank, regardless of whether they lived on a large block with extensive gardens and a swimming pool, or lived in a townhouse with one pot plant," he said.

"People can still do so."

"The difference is that the decision is now theirs to make."

Local councils will be able to retain mandatory rainwater tank requirements where they can prove a net benefit to the community.