The two classic outdoor sauna forms — barrel and cabin — heat the same way underneath, but the shape you choose shapes everything else: how much usable space you get, how it sheds a British winter, and how it sits in your garden. Here's what actually differs between them, and what to check before you buy either.
Barrel vs cabin: the structural trade-offs
A barrel sauna's curved wall gives you full standing headroom along the centre line, but that headroom tapers as you move toward the sides — a cabin's flat walls and ceiling give you the same clear height everywhere in the room, which tends to make better use of the corners for benching or a second tier.
The curve does one genuine practical job well: a rounded roof sheds rain and snow without a flat area for it to sit and pool on. That's a real advantage over a flat-roofed cabin — but many cabin saunas are built with a pitched roof specifically to solve the same problem, so it's fairer to think of this as "curved vs flat," not "barrel vs cabin" outright. If you're considering a flat-roofed cabin, ask how it's designed to handle standing water and snow load.
Cabins more commonly offer a full glazed gable end, turning a garden view into part of the experience — barrels can include windows but rarely at the same scale. On material efficiency, a cylinder does enclose a given seating capacity with somewhat less wall material and air volume than an equivalent rectangular room, though we'd treat any specific percentage saving you see quoted online with real scepticism — we couldn't verify the sort of numbers ('23% less air to heat') that get thrown around, and neither could the sites quoting them.
Electric or wood-burning heater?
Heat-up time
Electric heaters typically bring a sauna up to temperature in around 30–45 minutes; most manufacturer guidance tells you to allow at least half an hour. Wood-burning is slower and more variable — commonly 45–90 minutes depending on the wood, the draft and the stove — since you're managing a live fire rather than a thermostat.
What it costs to run
For electric, the maths is straightforward: a typical home sauna heater draws 4.5–9kW. At the UK's current Ofgem price cap (26.11p/kWh for the Jul–Sep 2026 quarter — this moves every quarter, so treat it as an illustration, not a fixed number), a session works out to roughly:
- 4.5kW heater, ~1 hour total: around £1.20 per session
- 6kW heater, ~1.5 hours total: around £2.35 per session
- 9kW heater, ~2 hours total: around £4.70 per session
Those are nameplate-power estimates (the heater doesn't run flat-out the whole time — the thermostat cycles it once it's up to temperature — so treat them as an upper bound), and they line up with the £1.50–£3.50 per session that UK retailers commonly report for real installations. Wood-burning running costs are harder to pin down honestly — estimates for firewood use varied by three times over between sources we checked, with no solid pricing behind any of them — so the fair thing to say is that wood is roughly comparable to, or cheaper than, electric per session if you're buying firewood, and can cost very little if you're sourcing and seasoning your own.
Getting it installed (UK)
Most UK homes run a single-phase 230V supply, and single-phase electric sauna heaters comfortably cover the range up to around 8–9kW (a 6kW heater draws roughly 25A, an 8kW around 33A). Above that, or with some heater brands, you may need a three-phase supply or a phase-conversion box — the exact threshold depends on the specific heater, so check before you buy if you're set on a larger unit.
Electric sauna heaters must be hardwired on their own dedicated circuit — no plug sockets are allowed in the sauna room at all. In the UK, a room containing a sauna heater counts as a special location under the wiring regulations (BS 7671), which makes the electrical work notifiable — it needs to be carried out or signed off by a registered electrician (NICEIC, NAPIT or similar), not a DIY job. Ask your electrician to confirm the current special-location requirements for your installation rather than relying on a number you've seen online — we found real disagreement between sources on the exact protection rating required, which tells you it's not something to guess at.
Upkeep
Electric heaters are genuinely low-maintenance — the heating rocks typically need replacing every few years, and there's little else to do. Wood-burning stoves need regular ash removal, a flue that gets swept, and a running supply of dry fuel — more ritual, more upkeep, and for many people, part of the appeal.
Ventilation, done right
Good ventilation isn't optional — it's how the heat and air actually move around the room, and it affects how the sauna feels as much as the heater does. The standard approach, confirmed directly against two real heater manufacturers' installation manuals, is fresh air in low (near or beneath the heater) and exhaust air out on the wall diagonally opposite. Where the two manuals we checked actually disagreed was exhaust height — one specified it high, near the ceiling, the other specified it low, below the upper bench — so "low in, high out" isn't a universal rule; follow your specific heater's installation manual rather than a generic diagram.
As a rule of thumb, the air in a sauna room should fully exchange around 5–6 times an hour — again, confirmed from real manufacturer guidance rather than a marketing blog. One genuinely useful practical tip that came out of the same source: keeping the upper vent closed while the room is heating up speeds up warm-up time, and the lower vent can generally stay open throughout.
Clearance and safety
Every heater has its own minimum clearance from combustible surfaces, and it varies more than you'd expect even within one manufacturer's range — we checked a real installation manual where clearance ran from 3 inches on the smallest electric model up to 5 inches on the largest in the same product line. Wood-burning stoves need meaningfully more clearance again. The only honest advice here is: check the installation manual for the exact heater you're buying, and don't assume a number you've seen for a different model applies to yours.
The same goes for the electrics — see the installation section above. A sauna heater circuit is notifiable work under UK regulations, and it should go through a registered electrician who'll confirm what applies to your specific installation.
Sizing yours
Rather than a rough "square feet per person" rule (we looked, and couldn't find one that traced back to an actual standard rather than repeated marketing copy), heater manufacturers size by room volume: roughly 1kW of heater power per cubic metre of room, adjusted upward for glass (which loses heat faster than an insulated wall) and any uninsulated surfaces. It's a more reliable way to check that a heater and room are actually matched than a generic capacity number on its own — worth asking about specifically when you're comparing options.
Whichever shape and heater you land on, the base matters as much as the cabin itself — a level, load-bearing surface is non-negotiable, and getting the electrics signed off properly isn't a step to skip.