Households improving their energy efficiency by two bands would receive a £100-a-year council tax cut for 10 years under plans launched by the Welsh Liberal Democrats.
The move, which would incentivise green measures such as insulation, is expected to cost £24m over the course of the next Assembly term and improve the energy efficiency of 20% of Wales' housing stock.
Speaking ahead of a visit to Rockwool in Pencoed, Welsh Liberal Democrat Shadow Housing Minister Peter Black said:
"The Welsh Liberal Democrats will support hard pressed families by cutting their council tax bills.
“Wales desperately needs to improve the energy efficiency of its houses, which are some of the most poorly insulated in western Europe, but too often the upfront cost puts families off getting that work done.
“Our plans will help ease that burden, ensuring families feel the benefit through a double bill cut: once on your Council Tax, and once on your energy bill.
“Welsh Liberal Democrats have the fresh ideas Wales needs to help people get on in life, as well as do our part to help tackle climate change.”