Welsh Lib Dems' £100 off council tax
Households boosting the energy efficiency of their homes would get a £100 a year council tax cut for 10 years under a Welsh Liberal Democrat pledge.
The party would give the cut to households that improve their energy performance certificate ratings by two bands if it were in power.
Lib Dems say the move would incentivise improvements such as insulation.
The policy would cost £24m over the next assembly term.
Peter Black, housing spokesman for the Welsh Lib Dems, said: "Wales desperately needs to improve the energy efficiency of its houses... but too often the upfront cost puts families off getting that work done."
A UKIP Wales spokeswoman said "for many families living on the poverty line, in substandard properties, or reliant on landlords to improve their energy efficiency, this is surely a kick in the teeth".
She added the Lib Dems have "always been namby pamby middle class idealists not living in the real world".
A Welsh Labour spokesman said: "Council tax bills in Wales are already £160 lower on average with Labour than in England under the Tories."
Plaid Cymru has promised radical changes to council tax, meaning hundreds of thousands of households in Wales would pay less.
The party's Adam Price said the Liberal Democrats' plans "will only perpetuate a system that is already grossly unfair".
The Welsh Conservatives' Jayne Cowan said: "It's impossible to take the Lib Dems seriously on council tax.
"Just last week they opposed our calls for a council tax freeze for all householders, now they're announcing a scheme which will cost almost as much to administer as it does in grants for the handful of homes it will help."