The chart below shows the heating rate for various hot tub size and heat source configurations. The figures show the approximate rise in water temperature (°F/hr) as well as the size and weight of the tub. A 4x3 is four feet in diameter and three feet tall.
- For powered hot tubs, the faster the heating rate will enable you to change your water and get back to soaking faster.
- For wood fired tubs this will help you understand how far in advance to plan your soak. If you're hot tubbing every day the tub will not cool down fully and you'll able to use a quicker fire to get back to temperature.
Tub Size | Gallons | Weight Full | Electric (5.5 kw to 10kw) | 125,000 BTU Gas Heater | Snorkel® Stove | Scuba® Stove |
| 4x3 | 209 | 1950 | 11 to 20 | 64 | 36 | |
| 4x4 | 290 | 2,670 | 8 to 15 | 46 | 26 | |
| 5x3 | 335 | 3,113 | 7 to 13 | 29 | 45 | 22 |
| 5x4 | 467 | 4,250 | 5 to 9 | 28 | 32 | 16 |
| 6x3 | 495 | 4,554 | 5 to 9 | 27 | 30 | |
| 6x4 | 686 | 6,195 | 3 to 6 | 19 | 22 | |
| 7x3 | 683 | 6,177 | 3 to 6 | 19 | 22 | |
| 7x4 | 947 | 8,455 | 2 to 5 | 14 | 16 | |
| 8x3 | 902 | 8,136 | 3 to 5 | 15 | 17 | |
| 8x4 | 1,251 | 11,110 | 2 to 3 | 11 | 12 |