Rexener Bioheater

Rexener Bioheater with energy saving kit (incl. in Silver, Gold and Gold Plus packages)

Calculate your savings

Normal prices: 2.090-3.390 €
Discounted prices valid until 30.6.2023

1 590,00 £2 690,00 £ / pcs

inc. 20% VAT
Rexener Bioheater

Rexener Bioheater

Press the button and adjust the temperature – Rexener Bioheater will heat up your hot tub or swimming pool in no time. The heating time of the water is considerably shorter than when heating with wood. The Rexener keeps the water temperature constant.

» Works with biodiesel, diesel or fuel oil.
» Low consumption. Maintaining a stable temperature is easy and inexpensive.
» Precise thermostat control 0–40 oC.
» Also for replacing existing wood stoves.
» Heats the water in no time.
» No visible smoke – suitable for use in residential areas.
» Efficient heating, 20 kW.
» Suitable for all outdoor hot tubs and even large swimming pools.
» Quiet, max. only 48 dB.

Energy saving kit (Included in Silver and Gold packages produced from November 2022)

The fastest and most energy efficient way of heating your hot tub or pool. Very easy to use. Suits any hot tub in the market. Save even more by using our energy saving kit.

Example: Use the energy saving kit to time the water circulation pump and Bioheater to run 6 times per day, for 1 hour at a time and save 2/3rds of already low energy costs.

Energy saving kit available as a spare part for older models.


3-Year warranty


SKU: N/A Category:

(incl. in all packages)

    You can get service from us in English, Swedish, Norwegian and Finnish.

(incl. in Bronze-, Silver- and Gold-packages)

The installation kit includes all necessary parts for installing the heater (sockets must be ready in the hot tub/pool).. We will go through these in our call with you.

Silver-Package includes Steinbach water circulation pump. Gold-package includes Steinbach mass filter, which also includes water circulation pump.

(incl. in Silver- and Gold-packages)


Rexener bioheater Basic

For you who already have a circulation water pump and installation supplies


Basic package

Installation kit

Circulation pump

Mass filter

1890 £


For you who already have a circulation water pump. This package is also great for swimming pools!


Basic package

Installation kit

Circulation pump

Mass filter

1990 £


The perfect kit for replacing the wood stove


Basic package

Installation kit

Circulation pump


Mass filter

2090 £


The perfect kit for replacing the wood stove. With mass filter.


Basic package

Installation kit

Circulation pump

Mass Filter


2290 £


Preinstalled in the larger wooden protective case


Basic package

Installation kit

Circulation pump

Mass Filter


3090 £


Rexener Bioheater can be installed on a new or existing hot tub or pool water heating system. Rexener Bioheater can replace the traditional wood-heated hot tub heater. Water heating can begin before the pool is full of water. This makes the heating faster.

You can use Rexener Bioheater with biodiesel, diesel or “red diesel”. You can also use Rexener Bioheater in a suburban area, as the heater will not cause visible smoke or smell that could disturb your neighbors. The high efficiency of Rexener Bioheater heater also means that the use of the heater does not cause much harmful exhaust emissions. In practice, the exhaust only emits carbon dioxide. The heater only needs about 80W of electrical power.

With Rexener Bioheater, you can keep the same water in your hot tub week after week by connecting a sand filter to the heater and using the appropriate pool chemicals. When the hot tub or pool is more convenient to use, the usage is more frequent. You can even get Rexener Bioheater from us with an installation service.

Rexener Bioheater also has the power to heat up a really large 50,000 liter swimming pool – all year round – even in Nordic countries! Rexener Bioheater is truly reliable and we give it a 3 year warranty.


Technical information

WEIGHT 43 kg
DIMENSIONS 38 × 58 × 86 cm
POWER 18,5 kW / hr
CONSUMPTION 2,0 L/h (Note: thanks to the thermostat, actual consumption is much lower)
FUEL Biodiesel, diesel or fuel oil
CONTROL Digital touch panel
TANK 30 l external tank
WATER CONNECTION 38 – 75 mm (38 mm inner diameter)
PIPE DIMENSIONS 100cm without pipehat and 110cm with pipehat.

Frequently asked questions

How much does the heater consume?


  • Hot tub volume: 1500L
  • Heating time from +7 °C to +38 °C takes about 2 hours, of which about 1 hour of water filling. During this time, consumption is 2 L per hour. Consumption = about 4 l biodiesel or diesel.

Note! The thermostat switches off the burner when the desired temperature has been reached, so that the heater does not consume any fuel. When the heat drops by 2-4 °C (adjustable), the heater restarts and it only takes a little while until the desired temperature is reached again. Therefor, consumption is also low and the use of the hot tub is economical.

If you wish, you can lower the temperature to +10°C if you do not use the hot tub/pool continuously. It saves energy.

Can I use the heater with seawater?


Rexener Bioheater should not be used with seawater as it can cause problems due to the high salinity and the warranty does not cover any damage that may occur.

It is strictly forbidden to use pool salt, for example to clean the pool. Pool salt can’t be added to water heated by Rexener Bioheaters.

Can I install the heater in an old hot tub?

Yes you can! Rexener Bioheater is suitable for all types of hot tubs

Can I heat my pool with this heater?

Yes you can! Rexener Bioheater heats up even larger swimming pools, up to 50 000 liters

Can I use biofuel?

Yes you can! Rexener works well with biodiesel.

Where can I find spare parts for the heater?

Our service covers the whole country. Our service car is constantly stocked with a comprehensive selection of spare parts. All Rexener spare parts are available from our warehouse.

Does the heater need a circulation pump?

Yes. The Rexener heater is so efficient that the heater does not operate optimally when in free circulation. If your pool (hot tub / pool) already has a circulation pump or sand filter system, you can take advantage of it with Rexener. If you do not already have a circulation pump or sand filter, you can easily order them from our online store while ordering a heater.

Where can I install the heater?

Rexener Bioheater can be installed up to 10 meters from a swimming pool or a hot tub. So it doesn’t have to be right next to the pool. The circulation pump handles water recycling.

It is good to place the heater in a place where it can be easily adjusted. It should be installed on a stable surface that is free of water. The heater feet are adjustable. The fuel tank requires a safe platform. Make sure the tank is located where it is easy to refuel.

What kind of circulation pump can be used with the heater?

Recommended circulation pump characteristics

Operating voltage 230V ~, 50Hz

Flow rate 6100 L / h 6 m.c.H2O

Highest flow rate 9.6 m.c.H2O

Minimum flow rate 2 m.c.H2O

You can also purchase a circulation pump from our websites.

Do I need to move the heater indoors in the winter?

It is not necessary to move the heater indoors in winter, especially if it is in use. If the heater is drained of water, it can also be stored outdoors.  Of course, it is always better to keep the device in a warm, sheltered place when not in use.

Does the heater have to be drained in winter (water / fuel)?

Water must not freeze inside the heater. If you wish, you can keep the water so warm that it does not freeze, so you do not need to drain the appliance. If the heater is not used (or the heat is not maintained), the unit must be emptied before frost.

The fuel remains in a weatherproof tank, so you don’t need to empty the tank even in frost. It is always advisable to change the fuel if the fuel stops for a long time.

In the frost, make sure that the heater uses winter grade fuel.

How do I drain the heater?

Behind the heater there is a drain plug for draining the water. So does the Rexener circulation pump.

Technical description

Comprehensive security systems

The electronically controlled safety functions of Rexener Bioheater ensure safe operation of the heater in all conditions. The security functions include: two overheating systems, a flame sensor, automatic shutdown and water level monitoring.

Water level monitoring system

If the heater does not have enough water, it will not turn on. If the water level drops too low, the heater burner will shut off.

Powerful oil burner

Air blowing fan and high-pressure oil injection ensure the reliability of Rexener Bioheater in all conditions.

The oil burner and the electric components of Rexener Bioheater are protected inside the heater’s casing. The design of the oil burner, the electronics that control it and the fuel tank take into account the Nordic weather conditions.

The oil burner fan supplies air to the combustion chamber into which fuel is injected. It is ignited by a lighter controlled by the electronics of the device.

The thermal energy of the oil is utilized to heat the water contained in the piping inside the heater. Efficient and precisely controlled combustion can utilize virtually 100% of the energy contained in the fuel oil, which means that Rexener Bioheater produces no particulate emissions or carbon monoxide. In principle, the exhaust will only produce harmless carbon dioxide.

Because all the energy contained in the oil can be utilized as heating power, the efficiency of the Rexener water heater is high, which means low fuel consumption.

The exhaust pipe (chimney) supplied with the heater ensures a very low sound level and safety. The hot flame of the oil burner is effectively protected inside the unit and the low temperature of the exhaust gases emitted from the exhaust pipe poses no risk of fire. The “chimney hat” at the end of the exhaust pipe also protects the burner from damage caused by air pollutants and moisture.

Precise temperature control

Rexener water heater is set to the desired water temperature between 0 and 45 degrees (C). The heater automatically maintains the set temperature.

Overheating systems

The oil burner will be turned off if the temperature of the water entering the heater reaches 50 degrees (C) or the temperature of the water in the heater exceeds 75 ° C.

Fire alarm and automatic shutdown of the system

Incorrect operation of the oil burner (poor combustion) activates the flame sensor, which shuts down the oil burner and the fuel pump. This ensures the safety of Rexener Bioheater in all situations.

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Reliable and easy to use

I would definitely recommend Rexener Bioheater to others. It is a top product. I am also very happy with the service I have received in connection with questions about the product. Rexener Bioheater will extend our bathing season, so we will use the bath throughout the year.

Pool season year round

Rexener Bioheater is heating up our swimming pool, whose volume is almost 50 m3. Rexener Bioheater has been easy to use and has significantly increased the use of the swimming pool.

Hot tub on an island

The customer lets the hot tub cool down during the week and he increase the temperature for the weekend when the hot tub is used. This makes its use really cost-effective. The heater quickly heats up the water to the desired temperature, and there is no need to worry about getting firewood.


21,00 £ / pcs

Heater supplies

Water hose, 40mm

17,30 £ / pcs

Heater supplies

Water hose, 38mm

15,40 £ / pcs

Heater supplies

REXENER fuel tank

60,00 £ / pcs


REXENER massfilter

175,00 £ / pcs

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