Marsun MHD20H 20 kW Diesel Generator with ATS and Heated Fuel Unit

The Marsun MHD20H is a three-phase 20 kW (22 kW maximum) liquid-cooled diesel generator with built-in ATS, a 70 l tank and a heated fuel block that makes the engine easier to start at low temperatures. By the manufacturer’s data this is its only difference from the MHD20, so take the MHD20H if the generator has to start in the cold; otherwise the MHD20 is enough. The 25 kW models, the MHD25 and MHD25W, have 5 kW more rated power but no heated fuel block.

Technical specifications

Download the manufacturer datasheet (PDF)

How the MHD20H differs from the MHD20, MHD25 and MHD25W

Choose the MHD20H if the generator has to start at low temperatures: the heated fuel block makes starting the engine easier, and the other main parameters match the MHD20. If you do not need the heated block, the MHD20 is enough. When the recommended long-term load (75–80 % of power) is above 15–16 kW, you need the 25 kW class: the MHD25 (27 kW maximum, 70 l tank) or the MHD25W (26 kW, 60 l tank), though neither has a heated fuel block.

How much fuel does the MHD20H use and how long does it run on a full tank?

According to the manufacturer, the Marsun MHD20H with its 70 l tank runs continuously for up to 8 hours. Use that figure when planning backup power.

A rough calculation from the specific consumption: 205 g/kWh × 20 kW is about 4.1 kg of diesel per hour, or roughly 4.9 l/h (diesel density 0.84 kg/l). By that formula a 70 l tank would last about 14.3 hours at full rated power. That is a theoretical upper limit, not a guaranteed run time: the manufacturer gives consumption as “less than 205 g/kWh”, and real consumption depends on load, temperature and engine condition. The generator shuts off automatically when 10 % of the fuel is left, and an additional fuel tank is available as an option for longer running.

Diesel generator with ATS: automatic start from a hybrid inverter

The MHD20H has a built-in ATS and a factory Two-Wire Switch dry-contact connector, so it can start and stop on its own without anyone present. There are two typical setups:

• Without solar panels. The ATS watches the grid. When the voltage drops it starts the generator and switches the site over, and when the grid returns it stops the engine and reconnects the grid.
• With a hybrid or off-grid inverter. The generator is connected to the inverter’s generator input. When the battery runs flat, the inverter sends a signal to the Two-Wire Switch connector and the generator takes over the load and charges the batteries.

Closing the contact starts the engine; opening it shuts the engine down safely. The manufacturer states compatibility with Deye, Solis, Solplanet, GoodWe, Victron Energy and Sungrow hybrid inverters. Connecting the generator to the building’s wiring and configuring the ATS must be done by a certified electrician.

How to connect a backup generator to a house

A generator is connected to the site’s internal network through a fixed connection. The MHD20H already has the ATS built in, so switching between grid and generator is automatic and no separate ATS unit is needed. ESO (Lithuanian grid operator) states:

“A generator may be connected to the internal electrical network of a whole building only by installing a fixed connection and measures that ensure the voltage produced by the generator is not fed into ESO’s networks… Entrust this work only to qualified specialists.”

ESO — Recommendations for installing a backup power source

ESO also advises choosing the power according to your connection capacity, and, when connecting single-phase loads to a three-phase generator, taking the single-phase limit into account, because the datasheet gives the combined power of all three phases.

We handle it for you. We select the equipment for your site, deliver anywhere in Lithuania, install and connect it.

3-phase diesel generator: how to spread the load across phases

The MHD20H powers both three-phase 400 V and single-phase 230 V loads, but it does not deliver full power on a single phase. Spread single-phase appliances as evenly as possible across all three phases and avoid large imbalance.

• Starting currents. Inductive loads such as pumps and compressors draw 2–5 times more current when starting than when running.
• Optimal load. Running at 100 % for long periods is not recommended. The recommended range for the engine and alternator is 75–80 % of rated power, for the MHD20H about 15–16 kW (25 % reserve).
• With battery storage. Add the power the generator will use to charge the batteries to the building’s demand.

Frequently asked questions

How long does the MHD20H run on a full tank?

According to the manufacturer, the Marsun MHD20H with its 70 l tank runs continuously for up to 8 hours. A theoretical calculation from 205 g/kWh at the full 20 kW gives about 14.3 hours, but plan around the manufacturer’s figure.

How much fuel does a 20 kW diesel generator like the MHD20H use?

The Marsun MHD20H has a specific consumption of less than 205 g/kWh, so at the full 20 kW it uses about 4.1 kg, or 4.9 l, of diesel per hour. At lower load consumption is lower.

Is the MHD20H a generator with ATS?

Yes. The Marsun MHD20H has a factory-fitted ATS: when the grid voltage drops it starts the generator and switches the supply, and when the grid returns it shuts the generator down.

Which inverters is the MHD20H compatible with?

The manufacturer states that the Marsun MHD20H is compatible with Deye, Solis, Solplanet, GoodWe, Victron Energy and Sungrow hybrid inverters. The start signal is passed through the Two-Wire Switch connector.

Can I connect the generator straight to my house’s distribution board?

No. The MHD20H must be connected to the building’s network only through a fixed connection with measures that stop voltage from reaching ESO’s networks, and only by qualified specialists. Hybrid Energy does this for you: we deliver anywhere in Lithuania, install and connect it.

Is the MHD20H suitable for a house, a farm or a building site?

Yes. The 20 kW Marsun MHD20H is made for backup power for homes and farms, building sites, solar systems with batteries and off-grid setups. Hybrid Energy helps you work out whether this power is enough for your site.

How loud is the MHD20H?

The manufacturer states a noise level of 72 dB for the Marsun MHD20H. Near homes, choose the generator’s location with the neighbours in mind.

Can I connect single-phase appliances to the MHD20H?

Yes. The MHD20H supplies 230 V single-phase as well, but you will not get the full 20 kW on one phase. Single-phase loads should be spread evenly across the three phases.

What is the optimal load for the MHD20H?

The optimal load for the Marsun MHD20H is 75–80 % of rated power, which is about 15–16 kW. Running at 100 % for long periods is not recommended.

How does the MHD20H differ from the MHD20?

The Marsun MHD20H is the same 20 kW generator as the MHD20, with built-in ATS and a 70 l tank, but it also has a heated fuel unit that makes starting easier at low temperatures.

Sources

• Marsun MHD20H manufacturer datasheet (PDF), checked 2026-10-26
• ESO — Recommendations for installing a backup power source, checked 2026-10-26