BRUSSELS - New energy economy standards could kick in for all new public buildings in the European Union from 2018, and for all new homes and offices from 2020, a source close to the EU negotiations said on Friday.

The new policy is expected to have a significant long-term impact on the EU's bill for gas imports, now worth about 85 billion euros ($126.4 billion) a year.

Final changes to the European Union's Energy Performance of Buildings Directive will be worked out at negotiations on November 17 between representatives of the EU's 27 member states and the European Parliament.

But several key compromises have emerged already.

The Parliament proposed that from the end of 2018, all new buildings would have to reduce their carbon footprint to zero. But member states said the goal was over-ambitious and impractical.

Instead, all public buildings built after 2018 must be low-energy, and after 2020 that will apply to all new buildings -- homes, restaurants, offices, schools, everywhere, said the source.

We're still fine-tuning the exact definition of low-energy, but it's clear it can't be the same for Finland as it is for Cyprus. There will be guidance on how member states calculate low-energy to take account of heating, cooling and hot water.

The policy has received little attention as it has weaved its way through the EU's complex political process, but it has the potential to make deep cuts into the level of European gas imports.

A similar EU plan to renovate about 15 million European buildings over the next decade is expected to slash back oil and gas imports by about 20 billion euros.

(Reporting by Pete Harrison, editing by Timothy Heritage)