How Can a 9 kW Sauna Heater Run on Iceland's Older 230 V Grid?

Key Takeaways

• A 9 kW heater runs on Iceland's older 3×230 V system only through a connection its maker lists.

• Harvia's manual for The Wall SW90 lists 230 V 3~ with 3 × 25 A fuses.

• The HUUM documents we checked for the DROP 9 show no 230 V 3~ diagram.

• A June 2024 parliamentary answer counted 454 service connections in Reykjanesbær still waiting for 400 V.

• HS Veitur aims to finish replacing its 230 V systems by the end of 2030.

• Only an electrical contractor authorised by HMS may take responsibility for the connection in Iceland.

A heater that's right on the order form can still be wrong for the street it lands in. We build outdoor saunas in Klaipėda and fit Harvia and HUUM heaters, so the supply question reaches us before the cabin is closed. The table below pairs each Icelandic supply type with the connection the heater makers publish.

How Can a 9 kW Sauna Heater Run on Iceland's Older 230 V Grid?

A 9 kW sauna heater can run on Iceland's older 3×230 V system through a 230 V 3~ connection, provided its maker lists one for that exact model. The house's service connection also has to carry the current. Harvia's manual for The Wall SW90 lists the connection with 3 × 25 A fuses, against 3 × 16 A on 400 V 3N~. The HUUM documents we checked list 3/N~400 V and 1/N~230 V only. Confirm the system with the distribution company, then agree the connection with the sauna manufacturer before production.

This article sets out what the operator and the heater makers publish. It doesn't replace the electrician.

Which parts of Iceland still have the older 230 V system?

The published evidence points to older neighbourhoods in Suðurnes. HS Veitur, whose distribution area includes Suðurnes, says so in its customer leaflet. “In the older part of town 3x230V voltage system is still in use, often called a two-phase system.” Most houses today, it adds, are connected to a 3/N 400V system.

The figures come from a written answer to the Althingi by Iceland's Minister of the Environment, Energy and Climate. It was received on 12 June 2024 and rests on HS Veitur's data. In Reykjanesbær 454 service connections still waited for 400 V, about 10% of homes. Sandgerði had 299, about 30%, and Vogar 84, about 17%.

All businesses and institutions on the Reykjanes peninsula already had 400 V connections. So the gap is in homes, which is where a garden sauna goes. The same answer says the 220 V system dominated Icelandic distribution until after 1970.

Treat those figures as a 2024 snapshot of one operator's area. HS Veitur's voltage-system page, read on 7 October 2026, sets a goal of finishing the 230 V renewal by the end of 2030. We found no published count for other Icelandic distribution companies, so we don't quote one.

How do you find out which system a house has?

Ask the distribution company first, and get the answer in writing. HS Veitur publishes an interactive map of the Suðurnes areas still on the older system, with a planned renewal year for each. Elsewhere, ask that area's distribution company.

Then let an electrician read the distribution board. Two readings decide the connection: how many phases arrive, and whether a neutral comes with them. A third, the main fuse rating, decides whether the house can carry it.

The notation is a clue. HS Veitur writes the older system as 3x230V and the newer one as 3/N 400V. The N is the neutral, and the older notation carries none.

Don't accept “it's normal 230 volts” as an answer. HS Veitur notes that the electricity inside the house is still 230 V after conversion. At a socket, both systems look the same.

Which connection do heater makers list for 9 kW?

Each maker publishes its own list, and the lists differ. As read on 7 October 2026, the table uses Harvia's installation manual for The Wall SW90. For HUUM it uses the DROP manual, the UKU 4.2 control manual and the DROP product page. HUUM's own table rates the DROP 9 at 8.5 kW.

Harvia's wiring figure shows one terminal block linked three different ways, one for each supply. Same heater. Different configuration.

A calculation of our own explains the jump from 16 A to 25 A. A balanced 9 kW load on 400 V draws 9,000 W ÷ (1.732 × 400 V), about 13 A per phase. On 230 V between phases it's 9,000 W ÷ (1.732 × 230 V), about 22.6 A.

The heat is the same. The current in each phase is about 1.7 times higher. On single-phase 230 V it's 9,000 W ÷ 230 V, about 39 A.

So the maker's connection table decides how a 9 kW sauna heater can run on Iceland's older 230 V grid.

The heater side isn't unique to Iceland. Norway raises the same question, and we covered it in Will Your Sauna Heater Work on a Norwegian 230 V IT Grid? We haven't found an Icelandic primary source that names the earthing arrangement of the older system, so we don't name it.

What does the older system mean for the service connection?

It means the sauna takes a larger share of a main fuse the whole house runs on. Harvia's table asks for 16 A per phase on 400 V 3N~ and 25 A per phase on 230 V 3~.

HUUM's manual puts the check first: confirm “that the maximum amperage of the main fuse matches the heater parameters”. Whether it does is the electrician's load calculation, not a dealer's estimate.

If the service is single-phase, there's a route. HS Veitur says such a connection can in most cases be changed to three-phase, and that an electrical contractor submits the request through HMS.

Why agree the connection before production, not at installation?

Because the three connections aren't the same cable. Harvia's table gives a minimum connection cable of 5 × 2.5 mm² for 400 V 3N~. For 230 V 3~ it's 4 × 2.5 mm². For 230 V 1N~ it's 3 × 10 mm².

Those are minimums for the heater's own connection. The feed from the house is the electrician's design.

At Wood Architects each sauna is assembled and checked at the factory before dispatch. In a factory-built cabin the cable route and the exit point are fixed during the build. So the supply system is a production input. A cabin prepared for one connection and delivered to another supply can mean reopening finished work on site.

Read the figure and the table together. Harvia's figure for the separately controlled SW90E shows a 230 V 3~ link position, but its table gives fuse values only for the other two connections. That gap is a written question for the heater maker.

What the manufacturer should send back to the electrician is covered in What Information Should a Sauna Manufacturer Give an Electrician?

What should you ask the customer's electrician?

Send these six lines before you place the order. A licensed contractor answers them, not you.

1. “Which supply system reaches this board, 3/N 400 V or 3×230 V, and has the distribution company confirmed it in writing?”

2. “How many phases arrive, and does a neutral come with them?”

3. “What is the main fuse rating, and how much of it can the sauna circuit take?”

4. “Is a voltage conversion planned for this address, and in which year?”

5. “Which heater connection will you use, and which page of the heater maker's manual shows it?”

6. “Which HMS-authorised contractor takes responsibility for the connection and reports its completion?”

The last line has a legal anchor in Iceland. HMS (Húsnæðis-, mannvirkja- og skipulagsstofnun) licenses electrical contractors. It states on island.is that only those it has authorised may be responsible for work on electrical installations. Act No. 146/1996 requires contractors to review their finished work and report its completion to HMS.

Do one thing before the next Icelandic order. Get the distribution company's written answer and a photograph of the distribution board, and send both to the sauna manufacturer with the heater's manual page.

A connection chosen from a document is a decision. One chosen on delivery day is a repair.

Frequently asked questions

Is Iceland's older 230 V system being replaced?

Yes. HS Veitur's website states a goal of finishing the renewal of its 230 V systems by the end of 2030. It publishes a map with a planned year for each remaining Suðurnes area. Outside Suðurnes, ask the distribution company for that area.

Does the conversion to 400 V give a house three-phase power?

Not by itself, on HS Veitur's description. HS Veitur says the electricity inside the house remains 230 V after conversion. Its leaflet says the change opens the possibility of a 400 V three-phase connection. That connection is a separate request, submitted by an electrical contractor through HMS.

Can a 9 kW sauna heater run on single-phase 230 V in Iceland?

Harvia's manual lists a 230 V 1N~ connection for The Wall SW90 with a 50 A fuse and a minimum 3 × 10 mm² connection cable. HUUM lists 1/N~230 V with a 40 A fuse for the DROP 9. Whether the main fuse can spare that is the electrician's calculation.

Who is allowed to connect a sauna heater in Iceland?

The connection has to be the responsibility of an electrical contractor authorised by HMS. HMS states on island.is that only those it has authorised may be responsible for work on electrical installations, including changes and repairs. Under Act No. 146/1996 the contractor reports the finished work to HMS.

Does the same heater model work on both Icelandic systems?

Harvia's manual shows The Wall SW90 linked for 400 V 3N~, 230 V 3~ or 230 V 1N~ on one terminal block. The HUUM documents we checked for the DROP 9 show 3/N~400 V and 1/N~230 V supplies. Ask the maker in writing about the exact heater and control unit.