Quick Answer: A 2025 University of Oregon study measured what actually happens inside your body during each — and a hot tub won on every metric that matters. Hot water immersion raised core body temperature by about 1.1°C, versus 0.4°C for a traditional sauna and almost no change for far-infrared, and only the hot tub session triggered measurable immune-marker changes. Saunas still have real upkeep advantages (cheaper per session, no water chemistry), but if you’re choosing one for the physiological payoff, the water wins.
Last updated: August 21, 2026.
“Hot tub vs sauna” usually gets answered with vague wellness-blog claims about both being “great for relaxation.” That’s true but unhelpful when you’re deciding where a few thousand dollars of backyard budget actually goes. In 2025, researchers finally measured the two side by side in the same study — and the numbers aren’t close.
Hot tub vs sauna by the numbers
- 1.1°C vs 0.4°C vs ~0.0°C — the core body temperature increase measured in hot water immersion, a traditional dry sauna, and a far-infrared sauna, respectively, in a 2025 study from the University of Oregon’s Bowerman Sports Science Center.
- 24x — water’s thermal conductivity relative to air, per the same research, which is the physical reason immersion heats the body faster than sitting in hot air even at a much lower air/water temperature.
- 150-195°F (up to 200°F) is a traditional sauna’s typical air temperature, versus 100-104°F for a hot tub’s water — the sauna runs far hotter, but transfers heat into the body far more slowly.
- $3,000-$10,000 is a home sauna’s typical installed cost in 2026, per HomeGuide’s pricing data, versus $350-$3,900 for the inflatable-through-plug-and-play hot tub range covered on this site.
Head-to-head comparison
| Factor | Hot Tub | Sauna |
|---|---|---|
| How it heats you | Water immersion (100-104°F) | Hot air or infrared light (150-195°F air, or cooler infrared) |
| Core temp rise (2025 Oregon study) | ~1.1°C | ~0.4°C (traditional) / ~0.0°C (far-infrared) |
| Immune-marker response | Measurable IL-6 change | Not measured in this study |
| Typical upfront cost | $350-$3,900 (inflatable to plug-and-play) | $1,000-$10,000+ (infrared to traditional install) |
| Monthly running cost | ~$30-$60 electricity | $8-$45, or $0.25-$2.50 per session |
| Water chemistry / upkeep | Yes — sanitizer, pH, filters | No water to maintain |
| Muscle/joint therapy | Jets + buoyancy | Heat only, no massage action |
| Setup | GFCI outlet, most models | Dedicated room or cabin, often 220V |
Why the hot tub wins the physiology test
Water conducts heat roughly 24 times more efficiently than air. Sit in a 175°F sauna and the surrounding air is scorching, but air is a poor heat conductor and your body sheds heat by sweating into it. Submerge in 102°F water and you can’t sweat your way out — the water pulls heat into your body continuously, which is why the Oregon researchers found hot water immersion pushed core temperature up nearly three times as much as a traditional sauna, and roughly infinitely more than the far-infrared session, which barely moved the needle. That larger core-temperature swing is also what drove the bigger cardiovascular response (higher heart rate, sharper blood-flow increase, higher cardiac output) and the only measurable immune-marker shift (a rise in IL-6 followed by elevated immune cell counts 24-48 hours later) in the study.
None of that means a sauna is worthless — dry heat still raises heart rate and circulation and plenty of people find it more comfortable to sit in for longer stretches without the water-immersion effect on blood pressure that some cardiac patients need to watch. It means that if your goal is the specific physiological response researchers can actually measure, water immersion currently has the stronger evidence behind it.
Who should get a hot tub
Intex PureSpa Plus (inflatable, budget entry point)
- Plugs into a standard household GFCI outlet — no dedicated room, no 220V circuit, no build-out.
- Delivers the stronger core-temperature and circulation response measured in the 2025 Oregon study, at a fraction of even an entry-level sauna's install cost.
- See our full best inflatable hot tub picks for sizes and price tiers.
Once the tub’s on order, try Amazon Prime free for 30 days so the test strips, filters, and any accessories you still need arrive before the first fill.
Who should get a sauna instead
A sauna makes more sense if you specifically want dry heat with no water chemistry to manage, longer comfortable sessions than most people tolerate at 102°F, or a lower per-session running cost — infrared units run about $0.25-$0.75 in electricity per session versus a hot tub’s continuous $30-$60/month draw. It’s also the better fit if you’re managing a condition where your doctor has flagged hot water immersion specifically (blood pressure, certain cardiac conditions) but hasn’t restricted dry heat exposure — that’s a conversation for your physician, not a blog post, but it’s a real reason some buyers choose sauna over tub.
The bottom line
If you’re picking one heat therapy purchase based on measurable physiological payoff, the 2025 University of Oregon research points at the hot tub: nearly triple the core-temperature rise of a traditional sauna, a stronger cardiovascular response, and the only measurable immune-marker change of the three heat types tested — all at a lower typical upfront cost ($350-$3,900 vs. $1,000-$10,000+) than a home sauna install. A sauna still wins on cheaper per-session running cost and zero water maintenance, which is a legitimate reason to choose it or add it later as a second purchase. Start with our best inflatable hot tub roundup, or if cost is the deciding factor either way, see how much does a hot tub cost for the full price breakdown by tub type. Weighing other categories too? Our hot tub vs pool and hot tub vs swim spa comparisons cover those buying decisions the same way.