Running a Hydrotherapy Spa Year-Round in the UK: Real Costs, Seasonal Challenges, and What the Evidence Supports

Buying a hot tub is easy. Running one year-round in the UK — through wet winters, energy price fluctuations, and the reality of maintenance — is where the real costs and decisions accumulate. This guide covers what no product brochure tells you: the seasonal running costs, the hygiene responsibilities, and whether the therapeutic benefits justify year-round operation.

Key Takeaways

• Year-round hot tub running costs in the UK range from £30–£90/month for hard-shell models and £40–£120/month for inflatables, with winter costs 20–50% higher than summer
• Insulation quality matters more than brand name — hard-shell hot tubs cost roughly half as much to run as inflatables because they retain heat better
• Hot tubs lose approximately 60% of their heat through the surface — a properly fitting cover is the single most cost-effective energy-saving measure
• Legionella bacteria thrive between 20°C and 45°C, making poorly maintained hot tubs a genuine health risk. Regular sanitisation is a legal requirement for commercial settings and a safety essential for home users
• The therapeutic benefit (warm water immersion at 40–42.5°C) is identical in summer and winter — cold weather does not enhance or diminish the evidence-based effects

Year-Round Running Costs: The Numbers Nobody Advertises

Hot tub sellers quote purchase prices. They rarely quote the ongoing costs that, over a typical ownership period, far exceed the initial investment. Here are the real figures for UK operation at current energy rates (approximately 27.7p per kWh as of early 2026).

Hard-shell acrylic hot tubs

Cost Category	Summer (Apr–Sep)	Winter (Oct–Mar)	Annual Total
Electricity	£25–£45/month	£40–£70/month	£390–£690
Chemicals (chlorine/bromine, pH)	£10–£15/month	£10–£15/month	£120–£180
Filter replacements	—	—	£30–£60
Water (refills 3–4x/year)	—	—	£20–£40
Total annual running cost			£560–£970

Inflatable hot tubs

Cost Category	Summer (Apr–Sep)	Winter (Oct–Mar)	Annual Total
Electricity	£35–£65/month	£60–£120/month	£570–£1,110
Chemicals	£10–£20/month	£10–£20/month	£120–£240
Filters/consumables	—	—	£40–£80
Water	—	—	£20–£40
Total annual running cost			£750–£1,470

The critical difference: inflatable hot tubs have minimal insulation, so the heater runs almost continuously in winter to maintain temperature. In cold weather, many inflatable models cannot reach or maintain 40°C — making them functionally unusable for therapeutic purposes during the months when warm water immersion might be most valued.

Why winter costs more

Heat loss is driven by the temperature difference between the water and the surrounding air. A hot tub at 38°C on a summer evening (18°C ambient) has a 20°C differential. The same hot tub on a January night (2°C ambient) has a 36°C differential — nearly double. The heater works proportionally harder, and your electricity bill rises accordingly.

Winter running costs typically increase by 20–30% for well-insulated hard-shell models and up to 50% for poorly insulated inflatables. The single most effective cost-reduction measure is a high-quality, properly fitting cover with an insulating core — hot tubs lose approximately 60% of their heat through the water surface.

What the Evidence Says About Year-Round Hot Tub Use

The therapeutic benefit of hot tub use comes from warm water immersion at 40–42.5°C. This temperature triggers the thermoregulatory mechanisms documented in multiple systematic reviews: peripheral vasodilation, core temperature decline, cortisol suppression, and parasympathetic nervous system activation (Haghayegh et al., 2019; Gholami et al., 2023).

These mechanisms operate identically regardless of the season. There is no evidence that using a hot tub in winter provides different or enhanced therapeutic effects compared to summer use. The ambient air temperature is irrelevant to the physiological response once you are immersed in water at the correct temperature.

What does change is the subjective experience. Many people find the contrast between cold air and warm water more enjoyable in winter — the feeling of getting into a hot tub on a cold evening is markedly more dramatic than on a warm summer night. This may increase the perceived relaxation benefit, even though the measurable physiological response is the same.

Evidence-supported benefits of regular warm water immersion

• Improved sleep: Warm immersion 1–2 hours before bed shortens sleep onset by ~10 minutes (Haghayegh et al., 2019 — meta-analysis of 17 studies)
• Pain relief: Warm water immersion improves pain and function in osteoarthritis, chronic low back pain, and fibromyalgia (Shi et al., 2023 — 32 RCTs, 2,200 participants)
• Stress reduction: Balneotherapy and spa therapy reduce cortisol levels (Antonelli & Donelli, 2018 — systematic review)
• Cardiovascular effects: Passive heat exposure improves vascular function (Brunt et al., 2024 — comprehensive review)

Claims not supported by evidence

• Weight loss: Sitting in a hot tub does not burn meaningful calories. Any weight loss during a soak is water loss through sweating, which is regained when you rehydrate.
• Detoxification: Your liver and kidneys handle detoxification. Warm water does not assist in “flushing toxins.”
• Immune boosting: There is no evidence that hot tub use enhances immune function.

Year-Round Maintenance: What It Actually Involves

Owning a hot tub year-round means committing to ongoing maintenance. This is not optional — it is a hygiene and safety requirement.

Weekly tasks (15–20 minutes)

• Test water chemistry (pH, chlorine/bromine levels, alkalinity) using test strips or a digital tester
• Adjust sanitiser levels to maintain 3–5 ppm chlorine or 3–5 ppm bromine
• Clean the waterline and check for biofilm buildup
• Inspect and rinse filters

Monthly tasks (30–60 minutes)

• Deep-clean or replace filters
• Check cover condition and seal integrity
• Inspect electrical connections and RCD protection
• Add anti-scale and water clarifier treatments as needed

Quarterly tasks (2–3 hours)

• Full drain and refill (every 3–4 months depending on usage)
• Pipe flush treatment before draining to remove biofilm from internal plumbing
• Clean the shell thoroughly before refilling
• Inspect the cover for waterlogging (a waterlogged cover loses insulating value and becomes dangerously heavy)

The Legionella risk: what you need to know

Legionella pneumophila — the bacterium that causes Legionnaires’ disease — thrives in warm water between 20°C and 45°C. Hot tubs operate squarely within this temperature range, making proper sanitisation essential rather than optional.

The Health and Safety Executive (HSE) provides specific guidance on controlling Legionella in spa pools and hot tubs (HSG282). Key requirements:

• Maintain sanitiser levels at all times — never leave warm water untreated
• If the hot tub will be unused for more than a week, either maintain full chemical treatment or drain completely
• Never leave warm, stagnant, under-chlorinated water sitting in a covered hot tub — this is the highest-risk scenario for bacterial growth
• Clean and disinfect filters regularly — biofilm on filters can harbour bacteria even when bulk water chemistry appears correct

For domestic home use, the risk is manageable with consistent maintenance. The risk becomes serious when maintenance lapses — particularly during periods when the hot tub is covered but not drained, such as during holidays or periods of reduced use.

Choosing a Hot Tub for Year-Round UK Use

Rather than recommending specific brands (which change model ranges frequently), here are the features that matter for year-round UK operation, ranked by cost impact. For a broader guide to choosing the right equipment for your goals, see our evidence-based equipment decision framework.

1. Insulation quality (biggest cost impact)

Full-foam insulation (where the entire cabinet interior is filled with expanding foam) provides the best heat retention. Partial-foam or reflective-barrier insulation is less effective. Inflatable models have minimal insulation by design.

The difference in annual running costs between a well-insulated hard-shell model and an inflatable can be £200–£500 per year — over a 5-year ownership period, superior insulation can save more than the price difference between the two product types.

2. Cover quality (second biggest cost impact)

A tapered, rigid foam cover with a locking mechanism and vapour barrier is essential. Covers should taper from 10 cm at the centre to 7 cm at the edges for water runoff. Replace covers when they become waterlogged (typically every 3–5 years) — a saturated cover loses its insulating value completely.

3. Circulation pump efficiency

A low-wattage circulation pump (50–100W) that runs continuously to maintain temperature is more energy-efficient than a high-wattage pump (1,500–2,500W) that cycles on and off. Many modern hot tubs use both: a small circ pump for maintenance heating and a large pump for jet operation.

4. Freeze protection

Any hot tub used year-round in the UK must have automatic freeze protection — a thermostat-controlled system that activates the pump and heater if water temperature approaches freezing. Frozen pipes can crack shells and damage pumps, resulting in repairs costing hundreds to thousands of pounds.

5. Electrical requirements

Most plug-and-play hot tubs run on a standard 13A socket but heat slowly and cannot run jets and heater simultaneously. Dedicated 32A or 40A electrical supplies (requiring professional installation, typically £300–£800) allow faster heating and simultaneous jet + heater operation — important for maintaining temperature during winter use with the cover off.

Cost-Saving Strategies for Year-Round Operation

• Always use the cover: Replace it promptly when waterlogged. A thermal floating blanket underneath the rigid cover adds further insulation.
• Lower temperature when not in use: Dropping from 38°C to 34°C when not using the tub reduces heating costs. Raising it back takes 2–4 hours rather than the 12–24 hours needed from cold.
• Position for wind shelter: Wind dramatically increases heat loss. Positioning a hot tub against a wall, fence, or in a sheltered corner can noticeably reduce winter running costs.
• Consider an air source heat pump: ASHP units can reduce hot tub heating costs by up to 70% by extracting heat from ambient air. Initial cost is £1,000–£3,000, with payback within 2–4 years for year-round users.
• Time your use: Using the hot tub in the evening (when you are about to sleep) aligns with the evidence for optimal sleep benefit — you get the therapeutic value and then cover the tub for overnight heat retention.

The Honest Year-Round Ownership Calculation

Here is a realistic five-year total cost of ownership for three common scenarios, including purchase, installation, running costs, and maintenance.

Scenario	Purchase + Install	5-Year Running Cost	5-Year Total	Cost Per Use (3x/week)
Inflatable hot tub (year-round)	£400–£800	£3,750–£7,350	£4,150–£8,150	£5.30–£10.50
Mid-range hard-shell (year-round)	£4,000–£8,000	£2,800–£4,850	£6,800–£12,850	£8.70–£16.50
Premium hard-shell (year-round)	£8,000–£15,000	£2,400–£4,200	£10,400–£19,200	£13.30–£24.60

Notice that inflatable hot tubs have the lowest purchase price but the highest running costs. Over five years of year-round use, a mid-range hard-shell model is often more cost-effective per use than an inflatable — and provides a meaningfully better therapeutic experience (pressurised water jets vs air bubbles, consistent temperature maintenance, and genuine year-round usability in UK winters).

When Year-Round Hot Tub Use Is Not Worth It

• If you will use it less than twice a week: At once-a-week use, cost per session roughly doubles. The running costs remain constant whether you use the tub or not.
• If you are not willing to maintain it: A neglected hot tub is a hygiene risk, not a wellness tool. If regular water testing and chemical treatment feels like a chore you will not sustain, do not buy one.
• If a bath achieves the same goal: For sleep improvement alone, a warm bath at 40°C provides identical thermoregulatory benefits. See our home equipment guide for cheaper alternatives. A hot tub adds convenience (no refilling) and social use, but the core therapeutic mechanism is the same.
• If energy costs are a serious concern: At current UK electricity rates, year-round operation adds £560–£1,470 to annual energy bills. If this figure is uncomfortable, a hot tub is the wrong purchase.

Related Reading

• Hydrotherapy Equipment: An Evidence-Based Decision Framework
• How Hydrotherapy Machines Actually Work: The Physics Behind Every Claim
• Home Hydrotherapy Equipment: What Works vs Marketing Fantasy
• Hydrotherapy for Relaxation: What Each System Does to Your Nervous System

References

• Haghayegh, S. et al. (2019). Before-bedtime passive body heating by warm shower or bath to improve sleep: A systematic review and meta-analysis. Sleep Medicine Reviews, 46, 124–135. PubMed
• Gholami, M. et al. (2023). Efficacy of hydrotherapy, spa therapy, and balneotherapy on sleep quality: a systematic review. International Journal of Biometeorology. PubMed
• Shi, Z. et al. (2023). Efficacy of aquatic exercise in chronic musculoskeletal disorders: a systematic review and meta-analysis. Journal of Orthopaedic Surgery and Research, 18, 917. PubMed
• Antonelli, M. & Donelli, D. (2018). Effects of balneotherapy and spa therapy on levels of cortisol as a stress biomarker: a systematic review. International Journal of Biometeorology, 62(6), 913–924. PubMed
• Brunt, V.E. et al. (2024). The multifaceted benefits of passive heat therapies for extending the healthspan. Temperature, 11(1), 1–26. PMC
• Health and Safety Executive (2017). The control of legionella and other infectious agents in spa-pool systems (HSG282). HSE