The average family is £11 a week better off last month compared to the same period last year, according to the Asda Income Tracker.
It is the largest year-on-year rise in the Income Tracker since June.
As a result, the average UK household had £162 a week of discretionary income in September – 7.5% higher that in the same month last year.
Annual inflation on food and non-alcoholic beverages is now at its lowest since May 2006, while utility bill costs fell over the year for the first time since comparable records began in 1988.
Electricity prices declined 7.2 per cent over the year to September and gas prices fell by 5.6 per cent.
Asda’s Pulse of the Nation survey showed more than 60 per cent of customers surveyed were not turning their heating on as much during the day, and more than 40 per cent were saving money by heating fewer rooms, despite the lower energy costs.
Asda president and chief executive Andy Bond said: “Although the increase in spending power is welcome, the spike in income this month is in part due to base effects from a year earlier. Unfortunately, we expect this month to mark the peak rise in income.”
Mortgage interest payments were 45.6 per cent lower in September compared with a year earlier.