Electric versus Diesel Directional Drilling Rigs

In the horizontal directional drilling (HDD) sector, electrification, hybrid power systems, and smart control and automation have emerged as the three main technology trends of the last 5–10 years. Urban infrastructure projects, carbon emission targets and fuel costs in particular are accelerating this transformation considerably. Let us take a technical look both at current developments and at the efficiency comparison between electric and diesel rigs.

Major developments in electric directional drilling rigs worldwide

1) Fully electric HDD rigs

In the new generation of rigs, all of the main systems can now run on electric motors.

For example:

• The electric HDD rig developed by MAX STREICHER GmbH & Co. KG aA
• The GRUNDODRILL JCS130E electrically driven HDD system

In these systems:

• Spindle (rotation)
• Thrust/pullback
• Mud pump
• Track drive

are all driven by electric motors.

This allows much lower CO₂ emissions, a serious reduction in noise, the ability to draw power from the grid on urban projects, and optimised energy consumption.

2. Hybrid (battery + generator) HDD rigs

Many manufacturers are moving to a hybrid architecture instead of going fully electric.

In the Danfoss + Normag hybrid HDD system, for example, the electric motor is designed as the main drive, while a diesel generator or battery support unit takes the load off the diesel engine in high-power operations so that it runs in its most fuel-efficient band — which can reduce fuel consumption by around 50%.

3. Battery or grid-powered HDD rigs

New rigs generally have three operating modes:

1. Direct grid power
2. Battery
3. Battery + range extender

The Goodeng GSE2000-LS Electric HDD Rig, for example, delivers 2,100 kN of thrust/pullback and 80,000 Nm of torque, yet achieves 30–40% savings in energy consumption.

4. Smart power management

The most important advantage of electric systems is load-adaptive power management.

Conventional hydraulic systems driven by an internal-combustion engine — especially those with fixed-displacement pumps — are extremely inefficient, because the machine has to produce the same power and burn the same fuel whether it is turning the rotary head unloaded or pulling a pipe at full load. Variable-displacement pumps offer a fairly reasonable solution by changing the angle of their pistons with the load, but since power is still regulated mechanically, efficiency remains lower than in electric systems.

• Smart inverters
• Regenerative systems (regenerative braking)

These allow the machine to reduce energy consumption when the load is low, running only the motors needed — which particularly cuts idling losses.

2. Electric versus diesel HDD rigs — efficiency comparison

The comparison below is based on average values from real field data and manufacturers’ technical reports.

Criterion	Electric HDD	Diesel HDD
Energy efficiency	85–95% motor efficiency	35–45% diesel engine
Fuel/energy cost	30–60% lower	High
Noise	Very low	High
Maintenance	Low (few moving parts)	High
Instant torque	Very high	Lower
Mobility	Limited by battery	High
Capital cost	20–40% more expensive	Cheaper

3. The energy-efficiency gap

Diesel system — typical HDD power train:

Diesel engine ↓ Hydraulic pump ↓ Hydraulic motor ↓ Mechanical motion There are losses at every stage:

• Diesel engine: 40% efficiency
• Hydraulic pump: 85%
• Hydraulic motor: 85%

Overall efficiency:

0.40 × 0.85 × 0.85 ≈ 29%

Electric system

Electric motor ↓ Gearbox ↓ Motion Efficiency:

• Electric motor: 90–95%
• Inverter + gearbox losses

Overall: ≈ 80–90%

This is why many manufacturers report 30–50% energy savings for electric systems.

4. Operational efficiency (field performance)

Advantages of electric HDD

1- High torque at low speed

The biggest advantage of electric motors over internal-combustion engines is that they deliver maximum torque immediately at around 1,000 rpm; they do not wait for the engine to build up speed like a diesel.

This is a major advantage in rock-drilling projects when using hole openers for rock reaming, because the hard-rock cutters on these tools need low speed and high torque to cut and grind efficiently.

2- More precise control

Inverter control (automatic load adjustment)

3- More stable drilling speed

Especially in the reaming passes after the pilot bore, it is important to find a steady rate of advance that suits the ground. Constantly varying power both wears the equipment through sudden loading and reduces efficiency. Because the response to an instantaneous load change is in the order of milliseconds, electric systems are extremely good at this.

Advantages of diesel HDD

1. They allow very long-distance operations; in the countryside it is still easier to carry diesel than electricity.
2. They make it easier to work on sites without grid power — and 90% of large rigs work in the countryside.
3. It is easier to build the HDD rigs used in very heavy rock-drilling operations (400–800 tonne range).

This is why diesel-driven HDD rigs are still favoured on large pipeline projects.

5. Future trends in the sector

1- Fully electric urban HDD

In terms of size and capacity, this rig group is the easiest segment of the sector to electrify. Cable projects of relatively small diameter generally use rigs in the 15–20 tonne band, which is advantageous both for size and for obtaining power in the city.

• Fibre-optic cabling projects
• LV and MV power lines
• Urban infrastructure

2- Hybrid large HDD

Hybrid rigs in the 300–800 tonne class

3- Autonomous and AI-supported drilling

Real-time geosteering may be a new concept, but it holds great promise for the sector. With artificial intelligence penetrating almost every area of life, it would be a surprise if pipeline projects — which require major investment and where even small improvements can create huge savings — did not get their share. Analysis of the drilling parameters and their projection onto the ground formation look likely to enable many optimisations that cannot be done by hand, although a little more time is needed.

6. Real field savings

According to field tests on hybrid HDD rigs, average fuel consumption is:

• Diesel HDD: ~35–40 l/h
• Hybrid HDD: ~18 l/h

In other words, fuel consumption can fall by around 50%.

In summary:

Electric HDD rigs:

• 2–3 times better in energy efficiency
• 30–60% lower in operating cost
• A very large advantage in emissions and noise

But in the large HDD rig class and on sites without grid access, diesel is still dominant.