How can you figure out how much it costs to run a diesel generator?

Diesel generators are essential for backup power in homes, businesses, construction sites, and industrial facilities. 

While they offer reliable electricity during outages, the cost of running a diesel generator can add up quickly. 

Whether you’re a business owner trying to manage expenses or a homeowner looking for an affordable backup power solution, understanding the total cost of running a diesel generator is crucial.

In this guide, we will break down all the factors that influence the cost of running a diesel generator, explain how to calculate these costs, and provide strategies to reduce expenses.

Key Factors Affecting the Cost of Running a Diesel Generator

To accurately estimate how much it costs to run a diesel generator, you need to consider multiple factors, including fuel consumption, generator efficiency, maintenance expenses, and more.

Diesel Fuel Consumption Rate

One of the most significant costs associated with running a diesel generator is fuel consumption. The amount of diesel a generator uses depends on:

• The generator’s size and power rating

• The load percentage (how much power you are drawing)

• The efficiency of the engine

For example, a 10 kW diesel generator typically consumes 2 to 2.5 liters per hour at full load, while a 100 kW generator might use 20 to 25 liters per hour. 

If the generator is running at half load, fuel consumption is usually 30-50% lower than full load.

Cost of Diesel Fuel

Fuel prices fluctuate due to factors like global oil demand, local taxes, and transportation costs. To determine your running cost, you need to check the current diesel price in your area.

For instance, if diesel costs $1.50 per liter, and your generator consumes 10 liters per hour, your fuel cost per hour would be:

10 liters × $1.50 = $15 per hour

If you run the generator for 10 hours a day, the daily fuel cost would be $150.

Generator Load Capacity and Efficiency

Generators perform differently at various load levels. Running a diesel generator at 50-80% of its rated capacity improves efficiency, while running it at low loads (under 30%) increases fuel consumption.

For example, a 50 kW generator at 75% load might consume 10 liters per hour, but at only 25% load, it could still use 6 liters per hour, making it less fuel-efficient.

Maintenance and Service Costs

In addition to fuel costs, regular maintenance plays a crucial role in overall expenses. Common maintenance costs include:

• Oil changes (every 200-250 hours): $50 - $200

• Air filter replacements (every 500 hours): $20 - $100

• Fuel filter changes (every 200-250 hours): $30 - $150

• Cooling system maintenance: $100 - $300 annually

• Major repairs (injector replacements, overhauls): $500 - $5,000

Neglecting maintenance can lead to breakdowns and increased running costs.

Generator Size and Technology

Newer diesel generators are more fuel-efficient due to advanced engine designs. 

A modern fuel-injected generator uses less fuel compared to an older, mechanically controlled unit. 

Choosing a high-efficiency generator can reduce running costs by 10-20%.

Environmental Conditions

Generators consume more fuel in extreme temperatures. In cold weather, diesel engines take longer to warm up, increasing fuel usage. 

In hot climates, generators work harder to cool down, leading to higher fuel consumption.

Step-by-Step Guide to Calculating Diesel Generator Running Costs

1. Determine the Generator’s Fuel Consumption Rate

Check the manufacturer’s specifications or conduct a test by:

1. Filling the fuel tank completely
2. Running the generator for one hour at a specific load
3. Measuring how much fuel was used

2. Find the Current Diesel Price

Search online for diesel prices in your area or check with local fuel suppliers. Prices can vary significantly by region and supplier.

3. Calculate Fuel Cost per Hour

Use the formula:

Fuel Consumption (L/hour) × Diesel Price per Liter

Example: If a 50 kW generator consumes 12 liters per hour, and diesel costs $1.50 per liter:

12 × $1.50 = $18 per hour

4. Estimate Cost Per kWh

The cost per kilowatt-hour (kWh) helps compare generator running costs with grid electricity.

Formula:

(Fuel Cost per Hour) ÷ (Generator Output in kW × Efficiency Factor)

Example: A 10 kW generator with an efficiency of 90% (0.9 factor) consuming 2 liters per hour at $1.50 per liter:

(2 × 1.50) ÷ (10 × 0.9) = $0.33 per kWh

If the grid electricity rate is $0.15 per kWh, running a diesel generator is more expensive.

5. Factor in Maintenance and Depreciation Costs

If a generator costs $10,000 and lasts 10,000 hours, the depreciation per hour is $1.00. Adding maintenance costs, the true cost per hour might be $2 - $5.

How to Reduce Diesel Generator Running Costs

Optimize Generator Load Usage

• Run the generator at optimal load (50-80%)

• Avoid running at low loads, which wastes fuel

Use High-Quality Diesel Fuel

• Low-quality fuel causes deposits and increases fuel consumption

Perform Regular Maintenance

• Change oil and filters on schedule to improve efficiency

• Clean the cooling system to prevent overheating

Invest in a Fuel Management System

• Smart fuel monitoring helps track usage and detect leaks

Consider Alternative Power Solutions

• Hybrid systems (solar + diesel) reduce fuel dependency

• Battery storage can supply power during low-demand hours

Conclusion

Running a diesel generator comes with significant costs, but by understanding fuel consumption, load efficiency, maintenance, and fuel pricing, you can accurately estimate expenses.

For businesses and homeowners relying on diesel generators, optimizing fuel efficiency and considering alternative energy sources can help reduce costs in the long run.

Would you like a cost breakdown for your specific generator model? Let us know!