The proposed one-off levy could raise over £5 billion to help support families in Powys as their energy bills sky-rocket.
The Liberal Democrats say the money raised could fund a substantial package of emergency support to help thousands of people facing higher bills.
This would include doubling the Warm Homes Discount and extending it to all those receiving Universal Credit or Pension Credit, giving 11,606 households in Powys £300 each off their heating bills this year.
The party is also calling for the winter fuel allowance to be doubled, benefitting 47,700 pensioners in the area and helping them keep their homes warm. On top of this, funding would be spent on helping people insulate their homes to slash heating bills in the long term.
Jane Dodds said: “It can’t be right that a few energy firms are making millions from record gas prices while people can't even afford to heat their homes as the cost-of-living crisis hits Powys hard.
“We know Powys is one of the worst hit areas in Wales for fuel poverty with an estimated 17 per cent of all households in Powys living in fuel poverty. The Government cannot look the other way any longer while families struggle to get by.”