From a rating and responsibility perspective, the answer is no.

A diesel generator supplied as standby power (ESP) is not intended, rated, or supported for 24-hour continuous operation — even if it runs at 1500 rpm.

This question causes confusion not because the machine itself is unclear, but because the word “standby” is used very differently by buyers and manufacturers.

What buyers usually mean by “standby generator”

In real projects, when a customer asks for a standby generator, they usually mean:

• The generator is not the main power source
• It starts immediately when grid power fails
• It supplies power during outages
• It is “backup” in the common-sense meaning

In short, from the buyer’s side:

“Standby” = when the grid goes down, the generator takes over.

This describes the role of the generator in the project — not its formal power rating.

What manufacturers usually understand as standby: ESP

From a manufacturer’s perspective, standby almost always refers to ESP (Emergency Standby Power) — a specific rating category with clear operating assumptions.

Under ESP conditions:

• The generator is intended for emergency use only
• Operating hours are limited and irregular
• The unit is not designed for continuous base-load operation
• Continuous daily running is outside the design assumption

This is not a semantic detail. It directly affects how the generator is selected, priced, documented, and supported after delivery.

Clarifying the ESP overload capability (often misunderstood)

ESP does not mean “no overload capability at all”.

In standard industry practice:

• ESP allows up to 10% overload
• The overload reference is based on PRP power
• The maximum duration is 1 hour

This short overload allowance exists to handle temporary emergency peaks, not to extend runtime or justify continuous operation.

It does not make an ESP generator suitable for 24-hour running.

Why 1500 rpm does not change the duty category

A very common misconception is that 1500 rpm automatically means continuous-duty capability.

That is incorrect.

1500 rpm only defines:

• The engine speed required to produce 50 Hz with a 4-pole alternator

It does not define:

• Allowed operating hours per year
• Duty cycle suitability
• Thermal margin for long continuous runs
• Maintenance intervals
• Warranty assumptions

A generator can run smoothly at 1500 rpm for many hours and still be operating outside its rated category.

What happens in real projects (where problems begin)

This is the most common scenario I see:

• The customer asks for a “standby generator”
• The manufacturer supplies the unit under ESP
• Pricing, documentation, and service assumptions follow ESP rules
• In real operation, the generator is used:
  • During frequent grid outages
  • For many hours per outage
  • Sometimes daily
  • Sometimes close to continuous operation

From the customer’s point of view, this still feels like backup use.

From the manufacturer’s and after-sales perspective, this is prime-power behavior.

That mismatch is where problems appear:

• Shortened maintenance intervals
• Accelerated wear
• Oil and thermal issues
• Warranty disputes

In real after-sales practice, when a generator is ordered under standby power (ESP), we usually reduce the maintenance interval to around 500 operating hours, because the rating itself assumes short, infrequent operation, not long continuous runs.

So can a standby generator run 24 hours?

The answer depends on how the question is framed.

From a purely mechanical standpoint:

• A water-cooled diesel generator can physically run for 24 hours under suitable conditions

From a rating, usage, and responsibility standpoint:

• A generator supplied as ESP should not be treated as a 24-hour continuous solution
• Using it that way means operating outside its intended duty category

This distinction directly affects:

• Maintenance planning
• Reliability expectations
• Lifecycle cost
• Warranty responsibility

The most important advice for buyers (and suppliers)

This point should be clarified before the order is placed, not after problems appear.

When a customer asks for a standby generator, they should clearly state one of the following:

• The generator is for temporary emergency use only
  (rare outages, limited hours, short runtime)

or

• The generator will run for long hours during outages
  (frequent failures, multi-hour or repeated operation)

If long or frequent operation is expected, the generator should be:

• Rated as prime power (PRP)
  or
• Configured, maintained, and supported with prime-power assumptions

Calling a generator “standby” does not change the operating reality — it only shifts risk.

Practical conclusion

A standby diesel generator running at 1500 rpm is not meant to operate 24 hours continuously under ESP rules.

If a project requires extended or frequent runtime during grid failures, the correct solution is not to stretch ESP limits, but to define the usage correctly from the beginning.

In real projects, choosing the wrong power rating causes far more problems than choosing the wrong engine brand.