British households could be owed an average of £117 for energy they paid for but did not use this winter.
Figures suggest that more than 11 million homes, or 42%, are in credit to their energy company.
Of those, nearly one in 10 could reclaim upward of £200, according to price comparison site uSwitch.
On the other hand, just under 14% of consumers, around 3.7 million households, have emerged from the winter in debt to their supplier.
Under Ofgem regulations, consumers are entitled to any credit on request, as long as they have provided up-to-date meter readings.
Energy suppliers may be forced to pay out £1.3 billion in total.
But some 38% of consumers are expected to leave the money in their account to cover price hikes.
Almost a third of customers believe they will struggle to afford the increased prices, while more than one in five say increases of £100 or more will force them into debt.
In the midst of increasing energy prices, millions of families have set about reducing their energy outlays.
Measures included turning down the thermostat, individual radiators and setting the heating to come on for less time every day.
The Conservative election manifesto is expected to include a promise to cut around £100 from energy bills by capping prices for the seven out of 10 households on standard variable tariffs.
Claire Osborne, uSwitch energy spokeswoman, said: "Under Ofgem rules, providers must repay any credit on request, so now is the time to read your meter, update your account and reclaim what you're owed."