Variables Within Your Control . Indoors vs. Outdoors . The location of your hot tub is a personal choice, and one that should not be decided solely on cost. There are some cost differences, however, between outdoor and indoor installation. Indoor room temperatures average 72 degrees, and as a result, indoor spas may save a little on electricity costs.
Most people prefer their hot tubs outdoors for pure enjoyment.
If the hot tub has proper insulation and energy saving features, an outdoor spa will not cost much more to operate than an indoor spa. In addition, outdoor spas can save money by eliminating the need for ventilation that indoor spas require. Water capacity of your hot tub. Although the difference between a 200 gallon vs. a 400 gallon hot tub is significant, the cost of operation is not twice as much. Water temperature in your hot tub .