The council reassessed rateable values, drainage charges and bills in order to try to find ways of reducing costs.
The review has resulted in 329,903 being recovered from the council's water supplier, as well as ongoing savings of 88,493.
A total of 52,379 has also been recovered from the authority's gas and electricity suppliers over the same period.
Additional annual savings of 12,235 through tariffs and charges have also been secured and work is continuing to find other ways of reducing the bills.
The savings will be a major boost to the council, which is facing a 90 million gap in its finances over the next three years.