National Australia Bank (ASX:NAB) said Tuesday that around 800 of its customers' existing properties will be assessed as part of a new Australian government-led trial for existing homes to assess their energy efficiency.

The trial is part of the government's expansion of the Nationwide House Energy Rating Scheme to existing homes, and it will test the tools and processes used to assess the energy efficiency of existing homes, ahead of a national rollout later this year, according to a statement.

The bank's customers applying to refinance or top up their mortgage will be invited to join the trial.

Each assessment will take place at the same time as a property valuation, and it will take around 30 minutes to 60 minutes. Customers will receive an assessment of their home's energy performance, as well as recommendations on how to improve their home's energy efficiency.