After your initial purchase and set-up costs, you must account for electricity and chemicals. The spa has heaters, pumps, and filters that require continuous electricity. Winter temperatures will also require more electricity than the summer months. To estimate the cost, you will want to obtain your rate per kilowatt hour and multiply it by the kilowatt hours in use. This equation will give you a monthly estimate. Additionally, you will need chemicals to keep your water’s pH balance in check. These can range from $10-$20 per month based on how often you use your tub.