Most people overlook that how you heat your hot tub ultimately affects how you use it and how much it costs you to run it. Given that different options and their use cases can get very confusing, I’ve written this article to dive deeper into this topic.
In this article, I will explain some of the options that you have for your DIY Hot Tub Heater. By the end of this article, you’ll know which option is the right one for you.
The Electric Spa Pack
The Spa Pack, often referred to as the heart of your hot tub, actually includes an electric heater. Many people don’t realize this, but almost all suppliers provide a Spa Pack with an integrated heater. So, if you’re relying solely on electricity to heat your hot tub, you’re already set with the electric heater built into your Spa Pack.
Beyond heating, the Spa Pack is an essential component of your hot tub setup. It acts as the control hub, managing everything from the jets and air blower to the filtration cycles. Think of it as the brains of your hot tub—it’s what keeps everything running smoothly.
That said, there are some downsides to using electricity as your primary heating method. One major drawback is the slow heat-up speed, which can test your patience. Another concern is the cost. As of 2025, global electricity prices have risen significantly, resulting in many people looking into other, more cost effective options.
Despite these drawbacks, the Spa Pack remains the simplest and most user-friendly way to heat a hot tub. Its convenience and all-in-one functionality make it a go-to option for those who prioritize ease of use in their DIY hot tub projects.
DIY Hot Tub Heater – wood burning
Another option that most people ask me about is a wood burning hot tub heater. I’d only recommend this for certain scenarios particularly where the setup is off grid and without a reliable energy source.
There are many occasions where having an off grid heating method for your hot tub is ideal. However, the main things to think about here are that if you are off grid, you are not going to have any pumps or jets. If you have no pumps or jets, then you are not going to have any filtration. With no filtration, you essentially have a bath that you are going to be emptying after every use.
The other thing you need to be mindful of here is that there is no thermostat in this setup. You are relying on the fire getting the tub to the right temperature and then being able to maintain it without “cooking you” – it is a challenge, believe me!
The amount of time needed to heat by a wood burning fire can be considerable if you have a large tub. Also, the amount of “work” involved in building the fire every time you want a hot tub can be too much for anyone (me included!)
Yes, it is certainly cheap, but it is not convenient in the slightest and you must have a lot of time on your hands.
What About Fire Pit Coils?
Firepit coils are a step up from the basic wood burner as a DIY hot tub heating method. These systems typically include a pump that circulates water through the coil, where it absorbs heat before being sent back into the tub.
Compared to a standard wood burner, firepit coils are more efficient and are often used as an auxiliary heating option alongside other systems. The inclusion of a pump also brings added benefits like filtration and cleaner water, making this method a more refined and practical solution for heating your hot tub.
That said, there’s still some effort involved. You’ll need to build and maintain the fire, which can be a bit of a challenge when you’re relaxing in the tub. Despite this, the efficiency and added benefits make firepit coils a great choice for anyone looking to upgrade their DIY hot tub heating setup.
DIY Hot Tub Heat Exchangers
Heat Exchangers are a great way in which you can harness heat that you are already generating or paying for in your home and then direct that into the tub. They essentially connect to your hot water or heating system of your home.
The hot water circulates around the heat exchanger heating up the “tubes” inside and then the heat gets transferred into the hot tub water that flows through the centre of the heat exchanger. A very simplistic explanation here but you get the idea. The waters of course do not mix – the hot tub water absorbs the heat offered by the heat exchanger.
Heat Exchangers are very efficient in that you are already heating either your hot water or your radiators or under floor heating in your home. In short, you are not paying twice to heat anything. This can mean huge energy cost savings in 2025 and beyond. They are also very good at putting out a lot of heat from a cost-effective unit. They are not expensive at all in terms of the heat that they will generate.
Heat Exchangers are usually added as a secondary form of DIY Hot Tub Heating as they are only useful for heating when you are using your home’s boiler. Therefore in the summer, they will be somewhat redundant and you’ll need another heating source.
The Fastest DIY Hot Tub Heater – Propane and Natural Gas
The more traditional way of heating a hot tub or a pool is with a gas or propane heater. They remain the fastest ways of heating up the tub being able to output a huge amount of heat.
However, with the cost of fossil fuels on the increase in 2025, many of us are looking for more efficient cheaper to run alternatives to propane and natural gas. However, these alternatives still are nowhere near as fast to heat up the tub.
If speed alone is what you are looking for, then propane or natural gas is for you. Furthermore, these can also be a suitable option for off grid systems though you will need to figure out how often and from where you will have your cylinders refilled.
The Most Economical DIY Hot Tub Heater – Air Source Heat Pumps
If you’ve checked out any of my other articles or watched my videos on YouTube, you probably know I’m a huge fan of Air Source Heat Pumps.
For me, they’ve completely transformed how I use my hot tub. I saw an 8x faster heat-up time compared to the old electric heater I used, and my running costs dropped by 66%. That’s not just a minor upgrade—it’s a game-changer. Imagine cutting down your waiting time to enjoy a soak and slashing your bills at the same time.
Now, while Air Source Heat Pumps do become less efficient in colder months, their overall performance still makes them a smart choice. They work on a simple yet ingenious principle: for every 1KW of electricity you put in, they can generate up to 6KW of heat. This efficiency is measured as the Coefficient of Performance (COP).
The COP is your efficiency guide—it tells you exactly how much heating energy you’ll get for every unit of electrical energy used. The higher the COP, the more cost-effective and eco-friendly the system. Even in cooler weather, their efficiency often outpaces traditional heating systems, making them a reliable option year-round.
One of the best parts? They’re not overly complicated to install. Most DIYers with a bit of technical know-how can manage it with the right guidance. Once installed, they require minimal maintenance, which means less hassle for you in the long run.
For me, Air Source Heat Pumps are the way forward as we head into 2025. They’re efficient, cost-saving, and eco-conscious—a triple win for hot tub enthusiasts looking to upgrade their setups. If you’re serious about maximizing your hot tub experience while keeping costs under control, this is the technology to watch.
You can check out popular air source heat pumps on my shop here.
Conclusion
Ultimately, the DIY Hot Tub Heater that you choose needs to fit you and your hot tub. It needs to fit how you plan to use the hot tub and how flexible you are in terms of your easy of use. I’ve created this table to summarise the different heating methods mentioned above with their pros, cons and best use case scenarios.
| Heating Method | Pros | Cons | Best Use Case |
| Electric Spa Pack | Simple to use and integrate (already included in most spa packs); low maintenance. | Slow heat-up time; expensive due to rising electricity costs. | Ideal for users prioritizing simplicity and integration over speed and cost. |
| Wood-Burning Heater | Off-grid option; inexpensive to run. | Time-consuming to set up and maintain; no thermostat; requires frequent water changes; no jets. | Best for off-grid setups or areas with no reliable energy source. |
| Fire Pit Coils | More efficient than wood burners; integrates pumps and filters for clean water. | Requires fire setup and maintenance; managing fire while in the tub can be inconvenient. | Suitable for cost-conscious users with some access to pumps and filters, looking for an auxiliary heater. |
| Heat Exchanger | Cost-effective; leverages existing home heating systems; high heat output. | Limited to times when the home heating system is active; redundant in summer. | Great for users looking to minimize costs while leveraging existing heating systems. |
| Propane/Natural Gas | Fastest heating method; suitable for off-grid systems. | Expensive due to rising fossil fuel costs; requires cylinder refills for propane. | Ideal for users prioritizing speed or off-grid setups with access to fuel sources. |
| Air Source Heat Pump | Extremely efficient (up to 8x faster than electric); lower running costs; easy maintenance. | Efficiency drops in colder months; higher initial installation costs. | Perfect for users looking for efficient, cost-effective, and reliable heating solutions year-round. |
For me, I chose an Air Source Heat Pump for my own hot tub. It saved me a lot of money (66%!) on the running costs of my tub. It fits my usage as it only takes a 90 mins or so to heat up which is ideal for how I use the tub. It will also maintain the heat in the tub too without me having to constantly maintain the temperature.
Hope you have found this article useful. If I can help you with your own DIY Hot Tub Heater, then feel free to reach out! It’s always better to have an expert opinion because it might help clear up many things before you begin!
Happy Hot Tubbin’