Operating costs of the Windsor International Aquatic and Training Centre are more expensive than initially predicted.

City officials estimated operating costs of about $1.5 million, but the actual cost came in more than double that number at $3.5 million.

City treasurer Onorio Colucci blames some of the increase on energy costs, saying hydro rates have increased about 40 per cent since budgeting for costs was done in 2011.

"Council has deliberately chosen to keep the fees very responsible - because again - it was not meant to be a for-profit enterprise, but be a family attraction for Windsorites."

Still, he is optimistic that operating costs can be lowered, adding that the facility attracted 200,000 people last year.