Everything you need to know about gas heat for hot tubs

gas heat for hot tubs

Gas heat for hot tubs? What is that all about? Hot tubs are a fantastic way to relax and unwind after a long day or week, and there’s nothing quite like soaking in warm, bubbling water to soothe sore muscles and calm the mind. But while hot tubs are a popular and beloved addition to many homes and properties, they do require some maintenance and upkeep to keep them running smoothly and efficiently.


One of the most important factors in maintaining a hot tub is ensuring that the water is heated to the right temperature. The ideal temperature for a hot tub is generally around 100-104 degrees Fahrenheit, but achieving and maintaining this temperature can be a challenge, especially in colder climates or during the winter months.


That’s where gas heat comes in. Gas heaters are a popular and effective way to heat hot tubs, providing consistent and reliable warmth that can be easily adjusted to suit your preferences. Whether you’re looking to warm up your hot tub for a relaxing evening soak or you need to heat it up quickly for a last-minute gathering or party, a gas heater can provide the heat you need when you need it.


In this blog post, I’ll take a closer look at gas heat for hot tubs, exploring how gas heaters work, the pros and cons of using gas heat, and some tips and tricks for maintaining your hot tub’s gas heating system. Whether you’re a seasoned hot tub owner or you’re considering adding a hot tub to your home or property, this post will provide valuable insights and information to help you make the most of your hot tub’s heating system. So sit back, relax, and let’s dive into the world of gas heat for hot tubs!

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How does gas heat for a hot tub work?


Gas heaters for hot tubs typically use either propane or natural gas as a fuel source to heat the water. The heater is connected to the hot tub’s plumbing system and uses a heat exchanger to transfer heat from the gas flame to the water in the hot tub.


Here’s a step-by-step breakdown of how a gas heater for a hot tub works:


  1. Gas supply: First, the gas supply (either propane or natural gas) is delivered to the gas heater through a gas line. The gas supply is controlled by a gas valve that regulates the flow of gas to the burner.
  2. Ignition: When the hot tub’s thermostat calls for heat, the gas valve opens and the burner ignites. The ignition source can be either a pilot light or an electronic ignition system.
  3. Combustion: The gas flame heats up the air inside the combustion chamber, which in turn heats up the heat exchanger. The heat exchanger is a series of metal tubes or plates that are designed to efficiently transfer heat from the combustion chamber to the water in the hot tub.
  4. Heat transfer: As the water from the hot tub passes through the heat exchanger, it absorbs heat from the hot metal surface of the exchanger. The hot water is then returned to the hot tub, where it raises the overall temperature of the water.
  5. Thermostat control: The thermostat in the hot tub constantly monitors the temperature of the water and adjusts the gas valve to maintain the desired temperature. Once the water has reached the desired temperature, the gas valve closes and the burner turns off until the thermostat calls for heat again.

What size gas heater do I need for my hot tub?


Determining the right size gas heater for your hot tub is an important consideration, as a heater that is too small may struggle to heat the water to the desired temperature, while a heater that is too large may be inefficient and lead to unnecessary energy costs. Here are the steps to follow to determine the right size gas heater for your hot tub:


  1. Calculate the volume of your hot tub: The first step is to calculate the volume of water in your hot tub. To do this, measure the length, width, and depth of your hot tub in feet and multiply them together. For example, if your hot tub is 7 feet long, 5 feet wide, and 3 feet deep, the volume would be 7 x 5 x 3 = 105 cubic feet.
  2. Determine the desired temperature rise: Next, you need to determine the desired temperature rise, which is the difference between the current temperature of the water and the desired temperature. Most hot tubs are set to a temperature of around 100-104 degrees Fahrenheit, so if the current temperature of the water is 70 degrees, the desired temperature rise would be 30-34 degrees.
  3. Calculate the BTU requirement: Once you have the volume of your hot tub and the desired temperature rise, you can use a BTU (British Thermal Units) calculator to determine the BTU requirement for your hot tub. A typical hot tub requires around 50 BTUs per gallon of water to achieve a temperature rise of 1 degree Fahrenheit per hour. So for example, if your hot tub has a volume of 105 cubic feet (approximately 785 gallons) and you want to achieve a temperature rise of 30 degrees in 1 hour, you would need a heater with a BTU rating of around 39,250 (50 BTUs x 785 gallons x 30 degrees = 39,250 BTUs).
  4. Consider additional factors: Finally, it’s important to consider any additional factors that may affect the size of the gas heater you need. For example, if your hot tub is located in a particularly cold or windy area, you may need a larger heater to compensate for heat loss. Similarly, if you plan to use your hot tub frequently or for extended periods of time, you may want to invest in a larger heater to ensure that the water stays warm and comfortable.

Overall, determining the right size gas heater for your hot tub requires careful consideration of several factors, including the volume of your hot tub, the desired temperature rise, and any additional factors that may affect the efficiency of the heater. By following these steps, you can ensure that you choose a gas heater that is properly sized to meet your heating needs and keep your hot tub comfortable and inviting year-round.


My top tip here may contradict somewhat what I have just written, but on most of the hot tubs that my customer build, 10’x10’ for example, I would recommend a 400K BTU heater as speed of heat up and “convenience” is more important than the science and theory behind it. Bigger is better when it comes to gas heaters for hot tubs.



What are the benefits of gas heat for my hot tub?


There are several benefits to using gas heat for your hot tub. Here are some of the main advantages:


  1. Quick heating: Gas heaters are capable of heating up the water in your hot tub quickly, which means you can start enjoying your hot tub sooner. Gas heaters can typically raise the water temperature by several degrees per hour, depending on the size of the heater and the volume of the hot tub.
  2. Efficient operation: Gas heaters are generally more efficient than electric heaters, which can help to reduce your energy costs over time. Because gas heaters use natural gas or propane as a fuel source, they are often less expensive to operate than electric heaters, especially in areas where electricity rates are high.
  3. Consistent performance: Gas heaters are designed to provide consistent heating performance, even in cold or windy conditions. Unlike electric heaters, which can struggle to maintain consistent heating in extreme weather, gas heaters are capable of producing a steady stream of warm water no matter the conditions.
  4. Durability: Gas heaters are built to last, with sturdy construction and high-quality components that are designed to withstand the rigors of regular use. With proper maintenance and upkeep, a gas heater can provide reliable heating performance for years to come.

What are the alternative heating methods for my hot tub?



There are several alternative heating methods to gas that you can consider for your hot tub. Here are some of the most common options:

  1. Electric heat: Electric heaters are a popular alternative to gas heaters for hot tubs. They work by using an electric element to heat the water. Electric heaters are generally less expensive upfront than gas heaters, but can be more expensive to operate over time, especially if you live in an area with high electricity rates.
  2. Heat pumps: Heat pumps work by extracting heat from the surrounding air or water and transferring it to the water in your hot tub. They are generally more efficient than electric heaters, but can be more expensive upfront than both gas and electric heaters.
  3. Solar heat: Solar heaters use the energy from the sun to heat the water in your hot tub. They are highly energy-efficient and can be a great option for those who live in sunny areas. However, they can be expensive upfront and may not be practical for those who live in areas with limited sun exposure.
  4. Wood-fired heat: Wood-fired heaters use wood as a fuel source to heat the water in your hot tub. They are highly energy-efficient and can be a great option for those who have easy access to firewood. However, they can be labor-intensive and may not be practical for those who don’t want to spend time chopping and storing firewood.
  5. Heat exchangers: Heat exchangers work by transferring heat from another source, such as a boiler or solar panels, to the water in your hot tub. They are highly efficient, but can be more expensive upfront than other heating methods.

Overall, the choice of heating method for your hot tub will depend on a variety of factors, including your budget, energy costs in your area, and personal preferences. By considering the advantages and disadvantages of each option, you can choose the heating method that is right for you and your hot tub.


Can I Help You?

If I can help you in any way I would love to hear from you. You can get in touch using the form below.

Thanks - Andi


Hi, Andi here. I own Buildahottub.com and also write all of the articles and info pages on the site. Some years back now, I built my own hot tub but struggled to find the information I needed. So, once my tub was complete, I started this website to help others in their own pursuit of hot tub and plunge pools DIY building information.

Today, I've helped over 700 DIY customers just like you all over the world build hot tubs and pools. Have a good look around the site, there are lots of resources here. Please do get in touch if I can help you. - Cheers, Andi

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