I am not the person sitting in the cab of the excavator. I am the person who sits in the back office, writes the purchase orders, checks the lease terms, and then explains to finance why we need another piece of yellow iron. That means this article is not a dealer brochure. It is a practical, opinionated comparison of the 240 Komatsu excavator and the 390 Komatsu excavator from the buying side of the desk.
Before we get into the details: I am writing some numbers from memory, and I will flag where I am not 100% sure. Always check the current Komatsu spec sheet for your region before making a decision.
Why These Two Komatsu Models End Up in the Same Conversation
When an operations supervisor asks for a Komatsu excavator, the discussion usually comes back to two model families: the PC240 and the PC390. The 240 is roughly 25 tonnes. The 390 is closer to 40 tonnes. They are not direct competitors in raw size, but they are the two names that keep showing up on the same requests, especially for a mixed commercial job.
The reason is simple. Many contractors want one excavator that can handle everything from utility work to bulk grading. If you buy too small, you end up renting a bigger machine for heavy lifts. If you buy too big, you pay for fuel and logistics you do not need. The real comparison is about where your typical site sits between those two extremes.
In my experience, the 240 is easier to justify on paper, but the 390 wins on any job where production is measured in tons per hour. That tension is why this comparison is worth having.
Dimension 1: Transport and Site Access
The 240 is the easier machine to move. I want to say the operating weight is around 24 metric tons, but don't quote me on it—the exact number depends on the boom, the arm, and the counterweight. It fits on a standard lowboy in most states with the right permits. The 390 is closer to 38 or 39 tons. Moving that through a tight city street is a logistics problem, not just a rental decision.
I almost made this mistake in 2022. We were pricing a job on a narrow residential street, and the operator kept saying 'just bring the 390.' The transport company took one look at the turning radius and said no. We swapped to a 240 and the job finished on schedule. Since then, I check access width before I check horsepower.
That said, on an open quarry or a highway site, the 390's footprint is not a problem. The point is not that the 390 is too big. The point is that 'bigger' has a transport and access cost that does not show up on the spec sheet.
Dimension 2: Digging Power vs Real-World Speed
Let's be honest about the 390. It has more horsepower, more breakout force, and a much bigger bucket. For heavy lifting, working against rock, or loading trucks on a large excavation, it is the better machine. I do not think anyone who has run both would argue with that.
But here is the part that surprised me. On a narrow sewer line job in 2023, the 240 out-worked the 390. The 390 could not complete a full swing cycle inside the trench shoring. It spent too much time backing away and repositioning. The 240 had enough reach for the trench and enough agility to keep cycling. By the end of the day, the 240 had moved more dirt in the space where the work actually was.
So the conclusion for this dimension is not 'the 390 digs harder,' which is obvious. The conclusion is that the 240 can be faster on confined sites. If your trench width and swing radius are limited, output depends on cycle speed and fit, not raw force.
Dimension 3: Operating Cost and Fuel Data
The 240 burns less fuel per hour. That is fairly obvious to anyone who has seen a small excavator run next to a large one. The more interesting comparison is cost per cubic yard of material moved. On a large cut-and-fill job, the 390's bigger bucket and higher production rate can make it cheaper per yard, even with higher fuel consumption. If you move thousands of cubic yards every day, the 390 may actually be the lower-cost choice.
Here is something dealers won't tell you: the first quote is rarely the final price for an ongoing relationship. Once you have proven that you pay invoices on time and your operators take care of the equipment, there is usually room to negotiate on freight, attachments, and service intervals. This applies to both the 240 and the 390.
What most people don't realize is that fuel efficiency on an excavator is not a fixed number. It depends on load cycle, idle time, and operator habits. Per FTC Green Guides, if a dealer makes a fuel or emissions claim, they should be able to back it up with evidence. Ask for the test data. I have learned that after one too many optimistic sales sheets.
Also, do not compare an excavator's fuel use to a Komatsu trash compactor. They are different tools with different jobs. A trash compactor is designed to crush waste and manage landfill surfaces, not to dig foundations. Comparing fuel burn between the two without mentioning the job is meaningless.
Dimension 4: Site Fit — Trenches, Landfills, and Pump Tracks
This is where the decision actually happens.
- Utility work: The 240. It is narrower, easier to balance with a trench box, and has enough arm reach for most shallow utility lines.
- Mass earthwork: The 390. Bigger bucket, faster cycle, fewer operating hours in the same calendar days.
- Landfill work: The 390 handles demolition debris and loading while a Komatsu trash compactor works the landfill surface. They are teammates, not competitors.
- Fine grading and pump track construction: The 240. Here is why.
What Is a Pump Track?
A pump track is a closed-loop dirt course for bicycles, with rollers and banked turns designed so riders can gain speed by pumping their body instead of pedaling. It started in mountain biking and has become common in parks and backyards. The key is in the shape of the soil. If the rollers are too sharp, the track feels bad. If the transitions are too flat, it does not flow. Building one is a fine grading job, not a mass excavation job.
A 240 can shape those transitions with a few inches of control. A 390 can also do it, but it is much harder to make small adjustments with that much weight and bucket force. I am glad we tested this before a pump track project in 2024. We almost took the 390 because it was available from the rental yard. A crew leader who builds tracks for a living told me the 390 would tear up the surface. He was right. So glad we switched to the 240.
How to Decide: A Few Scenarios
In my opinion, this whole comparison comes down to the site, the soil, and the schedule. It does not come down to ego.
Choose the 240 Komatsu excavator if you are doing mostly utility trenches, residential work, fine grading, or pump track builds. Choose it if you move machines often or if access is tight. Choose the 390 Komatsu excavator if you are doing bulk excavation for months at a time, lifting heavy materials, or working on open sites where cycle speed matters more than fuel cost.
If you are still not sure, rent one for a week. A dealer suggested that to us once, and it was the best advice I got. The rental cost is small compared to the cost of buying the wrong machine and fighting your operator for five years.
Since I took over purchasing in 2020, our team has brought in maybe 15 Komatsu machines, maybe 16—I would have to check the spreadsheet. The ones that stayed productive were the ones matched to a specific set of jobs, not the ones chosen for their bragging rights.
The industry is evolving. The old rule was simply 'buy the biggest excavator you can afford.' That made sense before GPS grading, telematics, and accurate fuel data. Today, you can match the machine to the cut and prove it with numbers. That does not mean the 240 is better than the 390, or the other way around. It means the question is still the same: what is the machine going to do all day?
Last thought. I have heard this exact debate at a Crane Club NYC meetup—a group where crane and rigging people trade stories and argue about equipment. One person will swear by the 390 for its power. Another will say the 240 is the only way to get work done on a tight site. They are both right, because they are both talking about their own job sites. The right choice is the one that fits your trenches, your access roads, and your operating budget.
Specifications and pricing change over time. Figures in this article are based on Komatsu published materials and my purchase history, accessed January 2025. Verify current machine weights, emissions data, and pricing with your local Komatsu dealer before ordering.
