Electric sauna heater review by a professional electrical engineer (Part II)

Please re-welcome Jeff back to saunatimes for Part II of his electric sauna heater review.  Jeff is an electrical engineer by trade. He has a high end job. I cannot reveal Jeff’s actual position. as I could be tracked down and interrogated by folks in black suits for breach of National Security. 

Enter Jeff:

In part 1 of this series (link here), we looked at various aspects of electric heaters. This includes sizing, styles, and design that differentiate some of these units.  In this post, we will explore some more of these topics, in addition to looking at construction and available amenities. For those looking for something a little more exotic, we will also take a look at gray market heaters.

Our previous post discussed how the overwhelming majority of electric sauna heaters are of the same basic design. These electric stoves don’t really have all that much to discriminate among them.  The market is dominated by two big companies, Harvia and Tylo-Helo, with rebadging of common units between model lines to create an appearance of variety.

On top of this, in general. only the blandest models have been certified for the North American market.   The manufacturers just don’t want to spend the money to certify a model unless they’re sure sales will justify the cost.  While understandable, it results in pretty pathetic selection for the North American sauna enthusiast.  Probably 80-90% of the models offered in North America are the same basic bland design; a wall-mounted box, deep rock cavity, 40 lbs of rocks, with three heating elements in direct contact with rocks.  Ho-hum.

same basic design of a conventional electric sauna stove

Two different product lines from Tylo-Helo, the Finnleo Designer (left) and the Polar HNVR (right), notice any similarities?  It’s not a coincidence.  In part 1 we show how Harvia markets the same unit under the Harvia and Finlandia brand names. 

Don’t get me wrong, this isn’t all bad.  There is an upside in that it does give the savvy consumer more options for bargain hunting.  If you’re on a tight budget and satisfied with the basic North American offering you can price shop among different “brands” and know you’ll get pretty much the same thing.  You may like the Finnleo but it’s only stocked by a few distributors.  You might find a deal or a close-out from some other distributor on the Polar (or visa versa).  It’s something to keep in mind as you steer through the marketing hype put out there from the manufacturers.

Electric sauna heater review: Tylo Units are Genuinely Unique

As mentioned in part 1, Tylo is the real outlier in that its units are genuinely unique.  We previously discussed the side chambers and staged heating elements but Tylo also uses unique chassis construction.  Tylo’s units have a carbon fiber surface coating that stays cool to the touch, unlike pretty much every other unit out there.  This means that Tylo’s don’t require a heater guard though Tylo does recommend you use one.

Heater guard on an electric sauna stove

Don’t want to use a heater guard like this for whatever reason?  Tylo’s cool touch surface coating means it isn’t legally required.

Tylo also is unique in that its remote control units house all the electronics within the heater itself rather than having a remote contactor box used by most of the others.  This certainly simplifies installation. However, I’m not sure this is a good thing in the big scheme of things, as the hot room environment increases wear and tear on the electronic parts themselves.  Tylo also has its own angular styling that is starkly different from the “box on the wall” look of most of the others.  Beauty is in the eye of the beholder, but I think they look pretty cool.  Plus, you don’t have to hide them behind a heater guard so people can actually see it and appreciate its appearance.

This isn’t meant to say that Tylo’s are better or worse than the others. But, they are definitely different from the standard North American offering.  If you are looking for some diversity in choice, they are worth checking out.  Fair warning, they are generally a bit more expensive than their equivalent “box on the wall” counterpart.

You Really Should Consider Lots of Rocks

Glenn has commented that he can tell an electric-heated sauna from a wood-burning sauna even if blindfolded. He equates an electric-heated sauna to sitting inside a toaster oven.  While I think his comment was somewhat tongue-in-cheek, the maestro does have a point.  However, I would suggest that the difference is not caused so much by the actual heat source, but by the rock quantity.  Heating a sauna with a blazing camp fire rather than a rock-filled stove wouldn’t be very pleasant either.

We got into the physics of rock quantity in part 1 and I won’t rehash that here. However, I will remind folks that rocks create thermal capacitance.  Sauna rocks store heat and provide for a soft, even release and distribution over time.  Take a look at some popular wood–burning stoves recommended for family-sized saunas below and note the rock quantity.

Sauna stove rock mass creating thermal mass for a better sauna experience

Now compare that to the typical electric box-on-a-wall heater that at most holds 44 pounds of rocks.  When it comes to thermal capacitance, these electric wall-mounted units just can’t compare to the wood-burning sauna stoves.  That’s the price you pay for convenience and compact size.  If you want to try and replicate the wood-burning feel with an electric heater, you’re going to have to increase the rock mass.  There really just isn’t any good way around this fact.

What I chose

For our sauna, we tackled this by selecting a floor-standing electric heater (rather than a wall-mounted unit) that holds up to 110 pounds of rocks.  It’s a 7 kW unit that is a little oversized for our 240 cubic foot sauna. We didn’t want to endure long warm-up times that would result from having such a large rock quantity.  Also, we made our sauna ceiling lower that the usual, averaging about 6 feet 6 inches.  We originally did this to minimize overall structure height.  I later realized this would also help with warm-up times as we aren’t wasting heat pooling well above our heads.

Our Harvia Virta floor-standing unit during a fit check, note the deep rock cavity (rocks and heater guard have not been installed at this point). Despite its size this unit only needs 2 inches of clearance around it so it fits in a really tight and compact space.

This isn’t meant as knock on the wall-mounted units. Wall mounted sauna heaters certainly have their place particularly if the budget is tight. However, there are trade-offs involved. There are other options available with large rock capacity that may be a better choice.  Check out some of the more exotic models available and don’t assume the predominance of the wall-mounted units means that they are necessarily the best way to go.

Other Amenities – Combi Units

Sharp-eyed readers may have noticed that our unit shown above is actually the Harvia Virta Combi as opposed to the standard Harvia Virta.  Combi units include a water tank and a dedicated heating element allowing higher humidity levels than typical Finnish sauna heaters.  You can still throw water on the rocks to create bursts of löyly in the traditional fashion.  However, in addition to setting the temperature level you can also set a precise humidity level higher than that usually used in saunas.

Harvia Virta Combi (left), note water tank with internal heating element in front of main heating elements. Tylo Sense Combi (right) has a water tank with built-in heating element located behind the rock cavity.

The idea behind these units is not to create a 100% humidity Turkish-style steam bath, as this would ruin most wooden saunas over time.  Instead, they create what’s caused a “soft sauna” with 40-60% humidity and lower sauna temperatures.  Combi units provide an extra degree of flexibility, particularly for those from different sweat bathing traditions.  I originally proposed this model to get my wife on board. Her ethnicity tends to favor steam whereas I wanted a dry Finnish sauna.  The Combi is a bit pricey, but overall is a small cost to keep my wife happy.

One of the really nice features of these units is that they can be set to automatically run a 0% humidity cycle to dry out the sauna immediately after steam bathing.  In addition, we’ve also included an exhaust fan in our sauna that is automatically activated at the start of the drying cycle to quickly remove residual humidity.  Both are controlled by the Virta Combi and should help prolong the life of the wood in our sauna.

One other thing to consider for outdoor saunas is that water remaining in the Combi tank could freeze if left unattended in cold climates.  This isn’t an issue for us in Southern California but something to consider if this applies to you.  The manufacturers recommend the user should drain remaining water after each use.

The “Always On” Sauna Heater

The “always on” sauna heater may be worth considering.  These units contain the rocks within a super-insulated cavity with a closable lid that keeps heat trapped inside the box.  There’s a low power heating element (usually around 200 Watts, about 4% of the main elements) that runs more or less continuously and keeps the rocks at sauna temperatures.  When you’re ready to sauna, you simply pop the lid open to quickly bring the sauna room to temperature.  Since the rocks are already hot, warm up only consists of that necessary to heat the air thus greatly reducing warm-up time.  Once opened, the main heating elements kick-on as needed to maintain the rocks at sauna temperatures.  These units typically have fairy impressive rock quantities for lots of thermal capacitance.

The Harvia Forte (left), Finnleo Saunatonttu (center), and the Polar Saunatime (right) are always on units. The Saunatonttu is pretty cool-looking but I can’t help thinking of R2D2. As to the Polar “Saunatime”, I think our host might have something to say about that name.

There are two downsides to these units; the purchase price is relatively high (at least $2K, some upwards of $3k) and the potential operating costs.  If you sauna regularly (nearly daily) then the costs of operating the low power element should more or less pay for themselves in reduced high power element operation.  If you sauna maybe once a week or less, then the electricity cost perspective is not worthwhile.  As an example, the 200 Watt element on continuously for 24 hours will use 4.8 kW-hours of electricity, the same as operating a 4.8 kW high power element for one hour.

So even if you don’t use it often, your electric bill will look comparable to a standard electric heater being used daily.  Perhaps this doesn’t concern you, but it is something that should be considered when planning the sauna. And this electric sauna heater review is here to help.

Electric sauna heater review: Gray-Market Heaters

Suppose you just aren’t happy with the sauna heater selection in North America.  It’s understandable as the vast majority of those certified for our market are uninspiring compromises, designed to appeal to the most people possible.  It is as if every restaurant being a pizza parlor or burger joint.  I’ve singled out some notable exceptions (in my opinion) in this post and the previous one but what if one is looking for something more?  Take a look at this screen capture from a UK sauna distributor as part of this electric sauna heater review:

A UK sauna distributor going deep

Aside from a few exceptions (e.g. Harvia and Tylo), most of the brands aren’t even available in the US as these units haven’t been certified here.  Also consider that these brands have multiple product lines. You’ll see if you click through each of these tags, many of them can be seen in the screenshot.  We probably get 10% the choices available of the European consumer, and the choices we do get are the pizza and the burgers.  So why not buy from Europe?  It’s certainly possible though there are some real potential pitfalls.  I won’t discuss the legality of doing so as I’m not a lawyer.  If you choose to do so, it’s between your conscience, the insurance man, and our friends at the Underwriter’s Laboratory (UL).  Proceed at your own risk.

Power incompatibility

With this electric sauna heater review, power incompatibility is the main issue when buying from Europe.  The great majority of European units are configured for 400 Volt three-phase power, not the 240 volt single-phase power available in North America.  There are some 240 units available from Europe but the selection isn’t much better than that available here.  Most 400 Volt units likely can be converted to North American power as the single-phase voltage forms are comparable.  (Each “leg” of 400 volt 3-phase power is 230 volts, virtually identical to the 240 Volts available here.)  However, they will almost certainly require additional contactors, fusing, and rewiring.  It’s definitely not a job for amateur hour.

Notation and wiring denoting 400 Volt 3-phase power from a European Harvia unit. This won’t work in North America without being reconfigured.

Further, North American units require a self-contained over temperature sensor that shuts the unit down in the event the inside of the heater gets too hot (usually 240 deg F).  European units don’t have this. They rely on the room temperature sensor for an over temperature trip.  Most of the European manufacturer’s seem to slap these on North American units as an afterthought and frankly they don’t seem to work very well.  Older Tylo units in particular have a reputation for tripping at much lower temperatures than they should.  In some documented cases, these trip at such a low temperature the sauna room can’t go much above 160 deg F.  The “fix” is to move the bulb sensor lower in the unit so it doesn’t get as hot.  I mention this as this safety feature seems to cause more problems than it actually solves.  Presumably the North American manufacturers (Saunacore, Scandia, etc.) do a better job with this.

More on grey market heaters

There are a few other odds and ends that a gray-market buyer must consider.  North American regulations limit interior sauna temperatures to 194 deg F (30°c.) and also limit the maximum sauna heater time setting to 1 hour.  European units wont meet these constraints as they will allow higher temperatures and longer times.  North America also requires a guard or grate over the top of the rocks.  European units won’t have this grate and they probably don’t even exist (in the event you wanted to obtain one) for units that aren’t certified for North America.  Violating these requirements will probably get you in trouble with the same guys who enforce the prohibition on tearing off those mattress tabs.

Last off, delivery can be an issue as the European distributors I contacted were willing to just get it to the US (for example a customs broker in New York) but wouldn’t ship it to my house.  That part I had to figure out myself.  I ultimately decided it was too much of a hassle.  You may find it worthwhile and the European prices are generally very good and quite a bit cheaper than comparable certified North American models.

Electric sauna heater review: conclusion

Thanks for reading and hopefully readers found this and the previous post helpful.  I would appreciate hearing from any readers that have brought in gray-market heaters and how their experience went.  Either leave a comment or send an email to Glenn so he can pass it along.

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