There are a number of factors that will affect the likely running costs of hot tubs and swim spas, including heat losses and usage. The greater the volume that needs heating, the higher the running costs. Water temperature is typically set between 36°C to 40o C, but in the summer, especially during very hot weather, this might be reduced to make the temperature more comfortable. The higher the water temperature is set, the more energy will be required to maintain it and therefore the higher the running costs. Find our more about the factors that effect running cost here.