How Long Does a Hot Tub Take to Heat Up?

There’s nothing quite like stepping into a perfectly heated hot tub, steam rising, bubbles swirling, and warm water melting away the stresses of the day. But if you’ve just filled your spa for the first time or are refilling it after a clean, you might be wondering: how long do you actually have to wait before you can dive in?

The short answer? Most hot tubs take between 4 and 8 hours to heat up to their optimal temperature. But that timeframe depends on several factors, from the ambient weather to the insulation quality of your spa. In this article, we’ll explore how long it really takes to heat up a hot tub, what variables influence heating time, and what you can do to speed up the process. Whether you're new to spa ownership or simply looking to optimise your setup, we’ve got you covered.

What’s The Ideal Hot Tub Temperature?

Before diving into heating times, it’s important to understand the target. Most hot tub users prefer water temperatures between 36°C and 38°C (around 97°F to 100°F). This is warm enough to soothe muscles and promote relaxation, but still safe for extended soaking. If children are using the hot tub, experts recommend keeping it slightly cooler, closer to 35°C. On the upper end, 40°C (104°F) is generally the maximum recommended temperature for adult use, and anything above that can be unsafe, especially with prolonged exposure.

So, How Long Does It Take?

On average, a hot tub will heat the water at a rate of about 3°C to 6°C per hour. This means that if you’re starting with cold water straight from the hose (typically around 10°C), you’ll be looking at approximately 6 to 8 hours to reach 38°C. However, smaller hot tubs or inflatable models with less water capacity may heat up more quickly, sometimes in just 3 to 5 hours.

The actual time can vary depending on several key factors. Let’s take a closer look at what might be speeding up or slowing down your spa’s heating process.

What Affects Hot Tub Heating Time?

• Outside Temperature: The climate plays a huge role. If you’re trying to heat your spa in the middle of winter, the colder air and lower starting water temperature will require your heater to work harder—and longer. On the other hand, in the warmer months, your hot tub may heat up noticeably faster.

• Insulation Quality: The better insulated your spa is, the more efficiently it will retain heat. High-quality rigid foam insulation helps prevent heat loss through the sides and base of the tub. A well-insulated hot tub can also maintain its temperature for longer periods, reducing the need to reheat and saving you money on energy costs.

• Hot Tub Size and Volume: Larger hot tubs with more water naturally take longer to heat up than smaller ones. Inflatable hot tubs, which typically have a lower water volume and thinner walls, may heat up quicker, but may also lose heat faster when not in use.

• Heater Power: Most home hot tubs are equipped with a 1.5kW to 3kW heater. The more powerful the heater, the faster it can raise the water temperature. Some high-end models feature rapid heating systems that significantly cut down warm-up times.

• Cover Usage: Hot tubs lose the majority of their heat through the water’s surface. Using a high-quality insulated cover while the spa is heating can make a huge difference, reducing heating time, improving energy efficiency, and helping to maintain temperature between uses.

How To Speed Up Your Hot Tub’s Heating Time

If you’re eager to soak sooner rather than later, there are a few simple things you can do to reduce the wait:

• Always use the cover: It might seem obvious, but using your cover during the heating process is the most effective way to trap heat inside and prevent it from escaping into the air. Make sure the cover is secure, in good condition, and fits tightly without gaps. If your cover is cracked, waterlogged, or poorly insulated, consider upgrading.

• Use a thermal blanket: Also known as a floating spa blanket, this lightweight sheet sits directly on the water’s surface beneath the cover. It adds an extra layer of insulation and helps retain heat more effectively, especially useful in colder climates or overnight.

• Turn on the jets: Activating your hot tub’s jets while heating improves circulation and helps distribute heat evenly throughout the water. Just make sure the cover remains on while the jets run.

• Check your heater and pump health: If your hot tub is taking longer than usual to heat up, it might be time for some maintenance. A worn-out heater or sluggish circulation pump can drastically reduce efficiency. Make sure filters are clean, components are working correctly, and settings are optimised.

• Avoid unnecessary heat loss: If your hot tub is located in a windy or exposed area, consider adding windbreaks, spa enclosures, or screens. Even a hedge or fence can help shield your spa from cooling breezes.

Should You Leave Your Hot Tub On All The Time?

It might sound counterintuitive, but for most people, keeping your hot tub running 24/7 is actually the more energy-efficient, and convenient, option. Once your water is up to temperature, maintaining it only requires small bursts of energy rather than large amounts to reheat from scratch.

Turning your spa off between uses might save a few pounds short-term, but the energy required to bring it back up to temperature could end up costing more in the long run. Plus, you’ll always have to wait several hours before you can use it again, which defeats the spontaneous, stress-free joy of spa ownership.

If you’re going away or won’t be using your hot tub for an extended period, you can turn the temperature down to around 30°C to conserve energy. Just remember to adjust it back up and allow enough time for it to reheat before your next soak.

More Advice on Heating Up Your Hot Tub

Heating your hot tub doesn’t have to be a waiting game. While the average spa takes between 4 and 8 hours to reach the perfect temperature, that time can vary widely depending on external factors, spa quality, and your maintenance habits. By using a good cover, maintaining your components, and considering additional insulation like thermal blankets or enclosures, you can cut down your heating time and save on energy costs.

And remember: for the ultimate convenience and energy efficiency, keeping your hot tub running consistently is often the smartest and most relaxing choice.

Looking to optimise your hot tub setup? At Wave, we offer a range of insulated hot tub covers, high-performance spas, and maintenance accessories to help you get the most out of every soak.