Nearly £130 million of government support is still available for claim, with organisations including Which?, National Energy Action and Fuel Bank Foundation supporting the final push to encourage voucher utilisation.
Latest figures reveal low voucher redemption rates in London, Scotland and the South East of England.
Government data shows a record-high number of redeemed vouchers, with over 83% now used.
Prepayment meter customers have already claimed nearly £650 million under the Energy Bills Support Scheme.
Amanda Solloway, Minister for Energy Consumers and Affordability, has urged households to use their vouchers worth up to £400 off bills before 30th June.