Setup
Electrical, cost to run, and sizing. The numbers that decide whether it works in your garage.
This is the part of the purchase that goes wrong. Not the choice of unit — the discovery, after it arrives, that the heater needs a circuit the garage does not have, or that the chiller runs all night in August and the bill says so.
None of this requires owning the equipment. It requires the manufacturer’s rated kW, Ohm’s law, the National Electrical Code, and a willingness to do the arithmetic in public. So that is what these pages are: the circuit math, the running cost, and a calculator that shows its working instead of printing an answer and asking you to trust it.
The obvious disclaimer, stated once: we are not electricians and this is not an electrical design service. The arithmetic here is correct and the code references are cited, but your installation is governed by your local authority having jurisdiction and belongs to a licensed electrician. Use these pages to know what to ask for — and to know when a quote sounds wrong.
Everything in Setup
Electrical Requirements
What circuit your unit needs, and the code rule that decides it.
Sauna Electrical Requirements
Every common heater size, its amperage, and the breaker the 125% rule requires.
Does a Sauna Need a Dedicated Circuit?
Short answer yes, and the reason is a load calculation you can do in your head.
Cold Plunge Electrical Requirements
Most chillers run on a standard 120V outlet - but GFCI, a dedicated circuit and no long cords still matter.
Does a Cold Plunge Need a Dedicated Circuit?
Usually not required by the unit, but a dedicated GFCI circuit is the safer, trip-free choice.
Cost to Run
What these units actually add to your power bill, computed from rated kW.
Cost to Run a Sauna
Monthly cost by heater size and session habit, at a rate you set yourself.
Cost to Run a Cold Plunge
Why a chiller costs less to run than people expect, and what actually drives the bill.
Tools
Calculators that show their work.
Sauna Heater Size Calculator
Room volume in, heater kW and required circuit out — with the arithmetic shown.
Do You Need a GFCI for a Cold Plunge?
Water and electricity means GFCI protection is the safety item that matters most on a plunge - what it does, where code calls for it, and the trip trade-off.
240V vs 120V Saunas
The single spec that decides whether you need an electrician - what 120V and 240V saunas can each do, and which one fits your space and panel.
Can You Use an Extension Cord for a Sauna or Cold Plunge?
Why a thin or long extension cord is a real fire and trip risk with heat and chiller loads - when a cord is acceptable, and how to size one safely.
Do You Need a Permit for a Home Sauna?
When a home sauna needs a permit and an inspection - the electrical work that usually triggers it, and why checking first saves money later.
What a Sauna Blanket Costs to Run
A sauna blanket is the cheapest heat therapy to run - roughly what a session costs in electricity, computed from typical wattage at a rate you set.
Cost to Run an Infrared Sauna
Infrared cabins sip power next to a traditional heater - what a session and a month realistically cost, from rated watts at your own electricity rate.
What It Costs to Fill a Cold Plunge
Water is the quiet cost of a plunge - roughly what it takes to fill and refill one, why you change it less than you'd think, and how to stretch a fill.
Do these three things, in this order
Almost every expensive mistake in this category comes from doing them in the wrong order.
1. Find out what your panel can feed.Before you choose a unit, not after. “Do I have two free slots?” is not the question — the question is whether your service has spare capacity across everything else in the house, which is a load calculation your electrician performs. Start here.
2. Size the equipment to that answer. A 4.5kW heater you can actually run beats a 9kW heater that needs a service upgrade. Our calculator works from the room you are planning and prints the circuit alongside the kW, so you can see the electrical consequence of the room before you build it.
3. Price the running cost at YOUR rate. Not a national average. The cost pages take the rate as an input for a reason we explain below.
The one rule that explains every number here
Nearly everything on these pages descends from a single idea: a continuous load. The NEC defines it as a load whose maximum current is expected to continue for three hours or more — which a sauna heater plainly is, and NEC 424.3(B) confirms fixed electric space-heating equipment is treated as one.
Once something is continuous, NEC 210.19(A)(1)(a) requires the circuit to carry “not less than the noncontinuous load plus 125 percent of the continuous load.” So you multiply the real draw by 1.25 and round up to a standard breaker size. That is it. That is the arithmetic the entire category leaves to your electrician to explain on the day.
| Heater | Draw | × 1.25 | Breaker |
|---|---|---|---|
| 6 kW | 25.0 A | 31.3 A | 35 A |
| 8 kW | 33.3 A | 41.7 A | 45 A |
The full table runs every common size, and this page explains why nothing shares that circuit.
What actually drives the cost to run
Not power. Duty cycle. This is the thing people get wrong, and it produces a genuinely counterintuitive result.
A 6kW sauna heater is an enormous draw for a small number of hours: three one-hour sessions a week, and the element cycles off once the room is at temperature. That works out to roughly $8.84a month. A 600W chiller is a modest draw that never really stops — holding temperature six hours a day, every day, whether you get in or not. That is about $20.62 a month.
The cold plunge costs more to run than the sauna does. Sessions versus standby, and standby wins. Sauna arithmetic · plunge arithmetic.
Why every calculator here asks for your rate
We default to 18.83cents/kWh — the US residential average for April 2026, read from the EIA’s own table rather than recalled. It is almost certainly wrong for you.
The same EIA table puts North Dakota at 12.35 cents and Hawaii at 46.62. A near-fourfold spread. Any site printing one national figure as “what it costs” is publishing a number that is wrong for almost every reader, which is why our default is labeled and dated everywhere it appears, and why the rate is an input rather than a constant.
What we deliberately will not tell you
Wire gauge. Ampacity depends on conductor material, insulation temperature rating, ambient temperature, bundling and run length. A gauge table we cannot verify against primary code text for your specific installation is a safety claim we have no business making.
Whether you need GFCI.NEC 210.8(F) (2023) covers outdoor outlets on single-phase circuits 150V-or-less to ground and 50A-or-less — which a 240V sauna circuit can fall inside — but the exceptions, and whether a hardwired heater counts as an “outlet,” are genuinely debated among licensed electricians. We state the principle and defer to your AHJ rather than split the difference by guessing.
That is the standard we hold everything to here: verify against primary text, or state the principle qualitatively and send you to someone licensed. Never split the difference by guessing.