What Size Electric Sauna Heater Do I Need?
Choosing the right electric sauna heater starts with your sauna, not the heater itself. The wattage you need depends primarily on the sauna's cubic footage, along with factors such as glass, insulation, and ceiling height.
Here's how to calculate your starting wattage, what can increase the requirement, and how to compare your result with available heater models.
How Is Sauna Heater Wattage Actually Calculated?
How Do You Calculate Your Sauna's Cubic Footage?
Start by multiplying length × width × height in feet to calculate your sauna's cubic footage.
For example: 6 ft × 5 ft × 7 ft = 210 cubic feet
This gives you the starting volume you'll use when comparing heater sizing charts.
If your sauna has an irregular shape, such as a sloped ceiling or separate open area, account for those spaces as well rather than relying only on the main rectangular dimensions.
What Is the Standard Wattage to Cubic Foot Ratio?
As a general starting point, you can estimate roughly 1 kW of heater output for every 45 cubic feet of sauna volume. Always verify the result against the manufacturer's published room-size range before choosing a heater.
For a 210-cubic-foot sauna: 210 ÷ 45 = 4.7 kW
That puts the baseline requirement at roughly 5 kW before accounting for factors such as glass or additional heat loss.
Use this calculation as a starting point rather than a fixed rule. Heater manufacturers use their own sizing charts and may account for room construction differently, so always verify your result against the specifications for the heater you're considering.
What Factors Increase the Wattage You Need Beyond the Base Calculation?
Glass, uninsulated surfaces, and unusually high ceilings can increase the heater capacity needed beyond the base calculation.
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Glass: Large glass doors or walls can increase heat loss.
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Insulation: Poorly insulated walls require more energy to maintain temperature.
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Ceiling height: A taller room increases the volume that needs to be heated.
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Multiple factors: If your sauna has several of these characteristics, check the manufacturer's sizing guidance carefully and consider the next available heater size.
How Do You Choose the Right Heater for Your Specific Room?
How Do You Measure Your Sauna Correctly Before Buying?
Measure the main box of the room first, then account for anything that changes the room's volume or creates additional space that the heater needs to warm, such as an alcove, an angled ceiling, or an open vestibule.
Grab a tape measure and record length, width, and height at the tallest point of the room. If you have a sloped or cathedral ceiling, calculate the actual average height of the space or use the manufacturer's recommended method for irregular rooms.
A separate changing area or vestibule connected by an open doorway should generally be measured and added in. Most real saunas aren't a perfect box, so building in this extra step now saves you from an inaccurate wattage number later.
What Happens if You Undersize or Oversize the Heater?
An undersized heater may take too long to bring the sauna up to temperature and may struggle to maintain the desired temperature. An oversized heater costs more upfront and may be unnecessary for the space.
The goal is to match the heater to the sauna rather than simply choosing the largest available model.
Should You Compare Specific Brands Once You Know Your Wattage?
Once you know your target wattage, you can compare specific heater models that fall within the appropriate range. At that point, look beyond output and consider factors such as heater design, controls, stone capacity, installation requirements, and available features.
For a closer look at the brands we carry, see our guides to HUUM electric sauna heaters, Harvia electric sauna heaters, and Saunum heaters
What Does Heater Sizing Look Like in Real Saunas?
What Wattage Fits a Small 1 to 2 Person Sauna?
A typical small sauna, around 4 feet by 5 feet by 7 feet, comes out to about 140 cubic feet.
4 × 5 × 7 = 140 cubic feet
Using the starting ratio of 1 kW per 45 cubic feet: 140 ÷ 45 = 3.1 kW
That gives you a baseline calculation of about 3.1 kW, but available heater sizes and manufacturer specifications matter when choosing the actual model. For example, the Harvia KIP45W 4.5 kW electric sauna heater is rated for sauna rooms from 100 to 210 cubic feet, making it an option within this room-size range.
If the room has a glass door or other factors that increase heat loss, always check the manufacturer's sizing requirements before choosing a heater.
What Wattage Fits a Larger 4 to 6 Person Sauna?
A larger sauna, roughly 6 feet by 8 feet by 7 feet, works out to about 336 cubic feet.
6 × 8 × 7 = 336 cubic feet
Using the same starting ratio:
336 ÷ 45 = 7.5 kW
That gives you a baseline calculation of about 7.5 kW. For comparison, the HUUM DROP 9 kW electric sauna heater is rated for sauna rooms from 283 to 460 cubic feet, putting a 336-cubic-foot room within its published range.
As with the smaller example, room construction can affect the final heater size, so check the manufacturer's specifications before choosing a model.
Once you know your target wattage, you can compare specific heater models based on their published room-size ranges, controls, stone capacity, design, and other features.
The Bottom Line
Choosing the right electric sauna heater starts with your sauna's cubic footage. Use that calculation as a starting point, account for factors such as glass, insulation, and ceiling height, and then compare the result with the manufacturer's published room-size range.
Once you know the wattage range you need, you can compare heaters based on design, controls, stone capacity, installation requirements, and other features.
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Let customers speak for us
I haven't even built this sauna yet (Rainelle), but I have to give an ENORMOUS shoutout to Adora and especially KELLY for their help on this one. This was a big purchase for us, and these ladies went way out of their way to make it work out for us. The first sauna that showed up was badly damaged in shipping, and from what it sounds like - that is not typical. At all. So Kelly helped us to get it squared away, and it took what could have been a horrible customer experience into a fantastic one. Give this woman a raise!
We really like our sauna! Quality of the sauna seems decent. The quality of the accessories was not! The back recliner was all busted up out of the box.
My wife and I would occasionally sit in the sauna at our gym after a workout. It was hot but a little gross. I can't tell you how many times we bailed on the gym sauna session because someone else was playing their phone too loud, someone was breathing like they were gasping for air, someone decided to be shirtless in public, someone is weird or any number of other reasons. Loved the sauna feeling but HATED the gym sauna.
We bought a sauna for our home and installed it in our basement to escape the gym sauna experience. We absolutely love it! We sauna daily. Without the angst and frustration of hoping to avoid an awkward gross experience at the gym sauna.
If you are considering a sauna purchase, spend a little extra and get the WIFI enabled heater. This is the best way to make sure you get the benefit of owning a sauna. The app on our phone is easy to use. Just click the on/off button on the app and set your temperature to your desire. I like 171. My wife likes 153. Once it hits the temperature, the app will let you know. You can even turn on your sauna while you are on the way home from the gym. The WIFI version and the app make all the difference in usability and enjoyment of your investment. If we did not have the app and the WIFI version, we probably would probably skip 2/3 of the sessions we currently take.
The sauna is well made. Wood quality is excellent. Very few knots and blemishes. Hillsboro Almost Heaven saunas are a great choice for quality components, solid electronics, easy to use controls and an enjoyable sauna experience.
This is a standard kit sauna. I made several modifications but I am very satisfied with it so far. I have a few shingles left to install tomorrow and then will move onto to interior. MSW has been easy to work with and I recommend them.
I really love this sauna. I use it about four times a week to help me wind down before bed and calm my ego. Customer service at MySaunaWorld was great.
Assembly took me roughly 8–10 hours total over two days, and I’m not a particularly handy person. The step by step instructions video was straightforward and easy to follow.
I paired the sauna with the HUUM Drop 9 heater (the largest HUUM Drop), and it performs very well. I hired an electrician to install it (about $900 extra). It easily heats the sauna to 190°F plus. I personally like it around 180°F, which it reaches in about an hour. Also, you can pour water over the hot rocks to make the air hotter and steamier. Make sure to mount it low so that it can heat everything above it. (I mounted mine 6” from the ground to the base of the heater.) I love that I can start heating the sauna from my iPhone, even when I’m not on my home Wi-Fi.
I got the double-bench configuration going across the back of the sauna which lets two people lay down. The area around the lower bench is cooler which is nice to have different temperature seating options.
The sauna looks fantastic, smells great, and feels solid. I would recommend this sauna to a friend.
We love our new Almost Heaven Pinnacle barrel sauna!
Delivery was perfect, the assembly was a breeze, and the sauna fits perfectly in our space.
The only regret we have is not to have made this purchase 10 years ago!
I had been thinking about installing a sauna for quite some time. I kept going back and forth between framing one in or a prefab that I assemble. I spent several weeks going over the various websites looking at designs for both and writing out the pros/cons for each. After much deliberation, I reached out to My Sauna World to purchase an Almost Heaven Greyson.
It came way sooner than expected which was a good thing, so I had to arrange for my electrician. I assembled it very easily, with my wife holding just one panel, and then I ran into a problem. The last wall was short. It took a lot of head scratching and measuring and remeasuring as well as back and forth communication with both My Sauna World and Almost Heaven. It turned out that I had been sent 2 glass panels that were the same dimension when the 2 glass panels are actually designed with different dimensions. The new panel was sent out without question, and the rest of the assembly went easy.
I will say that the folks at My Sauna World were extremely responsive and did a great job as liaison back to the manufacturer.
Overall, I had a really positive experience, and we are very happy with the Greyson with the Harvia Spirit 8kW stove.
We also have the duckboard flooring (that is a must) sitting on top of the concrete floor. The back and leg rest are also recommended.
Note: this is advertised as a 3-4 person but in reality it is a good 2 person. And lastly, I grew up with sauna my whole life, starting with my grandpa’s wood burning sauna. This non insulated Greyson type will not get up to the same temperatures, but it does get the job done. Very pleased with the product and do recommend (to frame one in my self and buy a pre-cut kit would have cost a few thousand more overall)
Their customer service is refreshing in a world where most companies fail miserably with service. They should teach customer service to other companies and government agencies. We have only tested the actual product to make sure it works, but along the way, we had multiple questions and the replies were quick and helpful. The sauna was easy to assemble.
Frankly, I was stunned at the quality of this product. Equally stunning is how easily everything fits together. It’s well and I’m looking to an improved lifestyle.
Back rests are a nice size and fit perfectly in my Lugano 3-person sauna. They are very comfortable (especially considering they are wood) and make sitting in the sauna an even more pleasant experience. To think that they were added in free to my purchase of the sauna is hard to believe. Very pleased with customer service from My Sauna World.com !
Well built, good quality, reliable, and matches my barrel sauna very well
I purchased this since it was significantly more affordable than from the brands website. It arrived quickly and is function perfect. It's easy to install and looks great. I had issues with water leaking into the sauna before that used to annoy me. Now it stays completely dry and the wood also is protected from damage and weathering.
The best Sauna ever, and the quickest delivery, 100% recommend !!!!
Works exactly as advertised. Easy install and perfect coverage. Highly recommend.
Very good customer service. My sauna came as expected.