The Duoetto MK2 is the most sophisticated water heater available for adventure vehicles and boats here in Australia. It supports seamless operation on either 240V AC or 12V DC power. This means you can enjoy rapid heating when connected to shore power at a campsite or via a solar system, then switch to the more power-efficient 12V mode while on the road. The 240V mode will heat your water fastest β if you only need the 10 litres warmed for use, it can take 13β20 minutes, depending on the incoming cold water temperature.
Furthermore, this hot water system can deliver over 30 litres of comfortable warm water for showering or dishwashing. The actual mixed volume depends on the initial heating temperature and the amount of cold water mixed in.
In this guide, we'll break down the features and capabilities of the Duoetto MK2 water heater β ideal if you're considering it for your campervan, caravan, RV, or boat. This includes the energy required to reach your desired temperature, heating times, and other key aspects.
Duoetto MK2 (10L 12-240V) Water Heater Specifications
| Type of water heater | Point of use |
| Dimensions | 409 x 267 x 262 mm |
| Net weight (empty) | 7.4 kilos |
| Power requirements | 12V DC or 240V AC |
| Power consumption | 300W or 1000W |
| Water storage capacity | YES (10 litres) |
| Water storage pressure | 0.85 MPa |
| Water heating element | Incoloy 840 |
| Water heating control | Variable thermostat |
| Protective safeguards | Protected against over-temperature, over-pressure, corrosion, and others |
| Warranty support | 12 months |
The Duoetto MK2 (10L 12-240V) Water Heater is indeed one of the most advanced storage water heaters available for your campervan, caravan, RV, or boat. Its dual-voltage circuitry allows operation on either 12V DC or 240V AC power β 12V as a power-saving mode and 240V for faster heating.
The unit features a premium Incoloy 840 heating element that reaches up to 1000W for quicker heating. It can bring 10 litres of water to a comfortable warm temperature in about 14 minutes or to a very hot level in 39β45 minutes.
Once heated, the water stays warm for an extended period thanks to high-density polyurethane foam insulation around the steel storage tank. This insulation also minimises condensation and reduces exposure to air, lowering the risk of rust and corrosion. Moreover, the system includes robust safeguards against rust and corrosion, such as a glass-like enamel coating that creates a strong barrier between the steel tank and the water.
What's Included in the Duoetto MK2 Kit?
The kit includes all the essential accessories needed for setup and use:
- Duoetto MK2 water heater β The main unit, featuring a hot water outlet, cold water inlet, thermostat selector, digital LED display, power supply cable, and pre-drilled mounting holes.
- Pressure relief valve set β A safety device that protects against over-pressure and water backflow.
- Printed user guide β A booklet with technical specifications, installation instructions, and operating guidelines.
- Installation kit β Various components for securely mounting the unit to your preferred location, including mounting brackets, bolts, and washers.
How Compact and Durable Is This Caravan Hot Water System?
Compact Design
For a van accessory, the unit is relatively large, measuring approximately 409 x 267 x 262 mm. As a storage water heater, however, it remains quite compact, allowing you to easily install it in tight spaces such as under a kitchen sink or bed.
The unit weighs only about 7.4 kg when empty, making it straightforward to carry and mount on the wall of your campervan. But when filled with water, it weighs nearly 20 kg, so you'll want to mount it in a location capable of supporting at least 40 kg for stability and safety β especially on rough roads.
Rugged, Durable Build
Like the Aqueous hot water system we covered a few days ago, the Duoetto MK2 is Australian-designed and approved for the most extreme off-grid applications. This durability comes from several key features:
- High-impact plastic housing β A tough ABS material that resists shattering and breaking, highly essential for vehicles subject to high vibrations on rough roads.
- SPCC steel enamel tank β A glass-like porcelain lining that prevents rust and corrosion, ensuring a long service life.
- Single-weld construction β Provides superior structural integrity, allowing the tank to withstand high internal pressures and external stresses without leaking.
- Incoloy 840 heating element β A premium nickel-iron-chromium alloy highly resistant to heat, oxidation, and corrosion. It operates at higher temperatures without scaling or degrading, outperforming alternatives like stainless steel or copper.
- Polyurethane insulation β High-density material resistant to degradation and deformation. It keeps water hot for extended periods, reducing reheating cycles and extending the heating element's lifespan.
- Warranty support β The system comes with a 12-month warranty, so you can purchase with confidence knowing the manufacturer stands behind the product.
How Does the Dual Voltage 12V/240V Power System Work?
The Duoetto MK2 features one of the most convenient electrical systems available, supporting seamless operation on either 12V DC or 240V AC. You can use it on the 12V supply while driving or during the day when solar panels recharge your batteries, then switch to 240V AC for faster heating when connected to shore power.
Notably, this dual-voltage system includes automatic voltage detection. When both 12V DC and 240V AC are connected, the unit automatically prioritises and uses the higher-voltage AC supply.
Using the 240V AC Mode
When using an AC power supply, plug the integrated cable into a 240V/50Hz outlet. Then, set the thermostat to your desired temperature (between 30Β°C and 75Β°C) using the dial on the front. When powered on, the red "240AC Heating" LED will illuminate, indicating that the water is heating.
Using the 12V DC Mode
Use the digital control panel on the side (between the water inlet and outlet) when operating the unit on a 12V DC supply. Press the "+" or "β" buttons to set the thermostat to your desired temperature. The digital display shows the set temperature while adjusting, then switches to the actual water temperature during heating. When heating on 12V DC, the green "12DC Heating" LED illuminates, while the red "240AC" LED remains off.
Is the Duoetto MK2 Hard to Install?
Although it is a straightforward accessory, this storage water heater is moderately difficult to install due to the plumbing and electrical wiring involved. For this reason, we recommend hiring a professional to install it in your adventure van or boat.
If you have the appropriate skills, tools, and time, you can still DIY-install the system and enjoy hot water in your van or boat. However, you must:
- Install the unit in a location that can support double its loaded weight β approximately 40 kg, since the total loaded weight is about 20 kg (the unit empty plus 10 litres of water β 10 kg).
- Correctly earth the electrical wiring to prevent the risk of short circuits and other electrical faults.
- Connect the supplied pressure relief valve correctly to avoid potential damage from over-pressure.
- Supply other plumbing and electrical items needed for the installation, including components such as a thermostatic valve (or mixer valve), tubing/pipes, adapters, terminal connectors, and others.
How Long Does the Duoetto MK2 Take to Heat Water?
Once installed, the unit is very easy to use. Simply fill the storage tank with water and turn on the power supply. The dual-voltage modes heat water differently β each mode has independent circuitry: 240V AC provides rapid heating, while 12V DC is more efficient for battery use.
240V AC Heater Mode
The 240V AC mode is ideal for fast heating. To calculate the energy required (Q) to heat the water, use the formula:
Q = mass (m) Γ specific heat capacity of water (c) Γ change in temperature (ΞT)
In this scenario, the tank holds 10 litres of water (β10 kg); the specific heat capacity of water is 4184 J/kgΒ°C, while the temperature change (ΞT) depends on your settings. For example, heating 10 litres from 20Β°C to 75Β°C (ΞT = 55Β°C) requires:
Q = 10 kg Γ 4184 J/kgΒ°C Γ 55Β°C = 2,301,200 joules β 639.22 Wh (watt-hours).
Time taken (t) = Energy required (Q) Γ· Heating element power (P). With a 1000 W element: t = 639.22 Wh Γ· 1000 W β 0.64 hours (about 38β39 minutes).
12V DC Heater Mode
The energy required follows the same formula. For example, heating 10 litres of water from 20Β°C to 70Β°C (ΞT = 50Β°C) requires:
Q = 10 kg Γ 4184 J/kgΒ°C Γ 50Β°C = 2,092,000 joules β 581.11 Wh.
With a 300 W element: t = 581.11 Wh Γ· 300 W β 1.94 hours (about 1 hour 56 minutes).
Quick notes:
- Heating water requires the same amount of energy in both 240V AC and 12V DC modes (energy depends only on mass, specific heat, and ΞT β not on the power source).
- Heating 10 litres from 20Β°C to 70Β°C on 240V mode would take only about 35 minutes.
- 240V AC mode heats water over three times faster than 12V DC mode.
- 12V DC mode heats more slowly but puts far less strain on your battery bank compared to using a 240V AC inverter.
How Much Warm Water Do You Get from the 10L Tank?
The high-density polyurethane insulation keeps your water hot or warm for an extended period after heating. And when using hot water, the 10-litre capacity is not the only volume available for use. The most comfortable water temperature is usually 38β40Β°C. Therefore, the 75Β°C or 70Β°C water stored in the tank must be mixed with cold inflow to avoid scalding during showering, dishwashing, or cleaning.
Mixing hot water with cold inflow increases the total volume of comfortable warm water. This can be calculated using the following formulas:
Total mixed volume: Tmv = Vh + Vc, where:
- Tmv = total mixed volume of warm water
- Vh = volume of hot water from the heater
- Vc = volume of cold water added (from the main fresh-water tank)
Meanwhile, cold water volume (Vc) = Vh Γ (Th β Tt) / (Tt β Tc), where:
- Th = temperature of the hot water in the heater's tank
- Tt = desired target temperature of the mixed water
- Tc = temperature of the cold water from the fresh-water tank
Example 1: Target water temperature (Tt) = 40Β°C, hot temperature (Th) = 75Β°C, and cold water temperature (Tc) = 20Β°C. Vc = 10 Γ (75 β 40) / (40 β 20) = 17.5 litres. Total mixed volume (Tmv) = 10 + 17.5 = 27.5 litres.
Example 2: Tt = 40Β°C, Th = 70Β°C, and Tc = 20Β°C. Vc = 10 Γ (70 β 40) / (40 β 20) = 15 litres. Tmv = 10 + 15 = 25 litres.
Example 3: Tt = 38Β°C, Th = 70Β°C, and Tc = 20Β°C. Vc = 10 Γ (70 β 38) / (38 β 20) β 17.8 litres. Tmv = 10 + 17.8 = 27.8 litres.
Example 4: Tt = 38Β°C, Th = 75Β°C, and Tc = 20Β°C. Vc = 10 Γ (75 β 38) / (38 β 20) β 20.6 litres. Tmv = 10 + 20.6 = 30.6 litres.
Is the Duoetto MK2 (10L 12-240V) Water Heater Worth Getting?
If you're looking for the most convenient hot water system for your adventure van or boat, the Duoetto MK2 is undoubtedly an excellent choice. Its standout feature is the dual-voltage power system, which allows you to use 240V AC for rapid heating or 12V DC for direct connection to your battery bank without excessive strain.
Secondly, this system delivers over 30 litres of comfortable warm water after mixing hot and cold inflows, which is plenty for multiple showers on the go or a longer one after a demanding day.
Furthermore, it is built to withstand Australia's harsh off-grid conditions. It also includes multiple safety features to ensure reliable performance while completely off grid, such as protection against over-temperature, over-pressure, backflow, rust, and corrosion.
FAQ: Duoetto MK2 Water Heater
How long does the Duoetto MK2 take to heat water?
On 240V AC with the 1000W element, it can bring 10 litres to a comfortable warm temperature in about 14 minutes, or to a very hot level in 39β45 minutes. On 12V DC with the 300W element, heating from 20Β°C to 70Β°C takes about 1 hour 56 minutes.
Can it run on 12V and 240V at the same time?
The dual-voltage system includes automatic voltage detection. When both 12V DC and 240V AC are connected, the unit automatically prioritises and uses the higher-voltage AC supply.
How much warm water does the 10-litre tank actually deliver?
Once mixed with cold inflow to a comfortable 38β40Β°C, the 10 litres of stored hot water yields between 25 and 30.6 litres of warm water, depending on your heating and target temperatures.
Is the Duoetto MK2 difficult to install?
It is moderately difficult to install due to the plumbing and electrical wiring involved, so we recommend hiring a professional. DIY installers must mount it where the structure can support about 40 kg, earth the wiring correctly, and fit the supplied pressure relief valve.
Ready for hot showers off-grid? Get the Duoetto MK2 (10L 12-240V) Water Heater from Campervan Builders today.
