What is the prime and standby rating of the Atlas Copco QAS 25?

The QAS 25 delivers 20 kW prime power and 22 kW standby power. Prime rating applies to continuous use with variable load; standby rating is for backup applications with an average load factor of 70%.

What engine does the Atlas Copco QAS 25 use?

The QAS 25 is powered by an Isuzu 4LE2T 2.2-liter inline-4 turbocharged diesel engine running at 1,800 RPM. The 4LE2T meets EPA Tier 4 Final emissions without a diesel particulate filter, using DOC aftertreatment only.

What are the service intervals for the QAS 25?

Oil changes are due every 500 hours or 12 months, whichever comes first. Air filter and fuel filter replacement intervals are 500 hours. Major engine overhaul is specified at 20,000 hours under normal operating conditions.

Is the Atlas Copco QAS 25 EPA Tier 4 Final compliant?

Yes. The QAS 25 is EPA Tier 4 Final and CARB compliant, making it legal for operation throughout California and all U.S. jurisdictions without restriction.

How does the QAS 25 differ from the larger QAS 45?

The QAS 45 uses the Isuzu 4LE2X variant (turbocharged and aftercooled) delivering 36 kW prime from the same 2.2-liter displacement. The QAS 25's 4LE2T is turbocharged only — no aftercooler. Both share the same 67 dBA noise level and 75-gallon fuel tank, but the QAS 45 adds 80% more prime power.

What fuel does the Atlas Copco QAS 25 use?

The QAS 25 runs on diesel fuel. The integral 75-gallon fuel tank provides over 48 hours of continuous runtime at 75% load. No diesel exhaust fluid (DEF) is required — the 4LE2T meets Tier 4 Final without SCR aftertreatment.

Who services Atlas Copco generators in Northern California?

OnPoint Generators provides local service and maintenance for Atlas Copco QAS units across the Bay Area and Northern California. We maintain familiarity with the full QAS lineup including the Isuzu-powered models and offer faster response times than the Atlas Copco factory service network.

Atlas Copco · QAS Series

Atlas Copco QAS 25

Name: Atlas Copco QAS 25
Brand: Atlas Copco
Availability: PreOrder

22 kW standby / 20 kW prime · Diesel · Liquid-cooled

20 kW prime diesel portable generator. Isuzu-powered QAS series with 67 dBA operation, Leroy Somer alternator, and 75-gallon tank.

Standby power: 22 kW / 20 kW prime
Voltage options: 120/240V, 208V, 277/480V
Frequency / Phase: 60 Hz · 1/3-phase
Engine: Isuzu 4LE2T · 2.2L
EPA / Emissions: Tier 4 Final
Alternator: Leroy Somer LSA 40 M5

Commercialrental-fleettemporary-powerevents

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Overview#

The Atlas Copco QAS 25 is a 20 kW prime / 22 kW standby portable diesel generator from the Swedish-engineered QAS series. Powered by an Isuzu 4LE2T engine at 1,800 RPM, it pairs with a Leroy Somer LSA 40 M5 alternator delivering ±0.25% voltage regulation — tighter than the industry-standard ±0.5%.

At 67 dBA at 7 meters, the QAS 25 is 5-8 dB quieter than comparable portable generators in this class. The 75-gallon integral tank provides over 48 hours of runtime at 75% load, making it well-suited for multi-day construction operations and noise-sensitive urban job sites.

Leroy Somer alternator advantage#

The LSA 40 M5 alternator uses AREP (Auxiliary Regulated Excitation Path) technology to deliver ±0.25% voltage regulation — twice as tight as the ±0.5% industry standard found in most portable generators. This matters for sensitive electronics, lighting rigs, and any load where voltage sag causes problems. The Class H insulation (180°C continuous rating) provides a generous thermal margin at the QAS 25's modest 20 kW output, extending winding life in hot-climate deployments.

Combined with the Isuzu 4LE2T's fuel efficiency and the QAS series' compact enclosure design, the QAS 25 delivers one of the lowest cost-per-kWh figures in the portable 20 kW class.

Our service experience#

Atlas Copco builds some of the best-engineered portable generators on the market — the QAS series' sound attenuation, fuel efficiency, and voltage regulation are genuinely best-in-class. However, the brand's after-sale service network is a well-known weak point. Owners frequently report unreturned service calls, travel charges exceeding $311/hour, and multi-week waits for replacement parts.

For Atlas Copco QAS owners in Northern California, OnPoint provides local maintenance and repair service with significantly faster response times than the factory service network. We maintain familiarity with the full QAS lineup and stock common consumables for the Isuzu-powered models. If you own a QAS 25 and need service support that matches the quality of the hardware, contact us.

Engineering specifications

Acoustic

Sound @ 7m, 75% load: 67 dBA
Enclosure: Sound-attenuated

Fuel system & runtime

Integral fuel tank: 75 gal

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Lock the enclosure, fuel system, transfer switch, and add-ons — we'll confirm pricing, availability, and lead time within one business day. Prefer a free-form quote? That option is still here.

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Estimate runtime for the Atlas Copco QAS 25

Adjust load percent and tank size to estimate runtime. Pre-filled with this model's spec where available.

Estimate runtime on this tank

Generator size

Fuel

Fuel tank capacity

gal

Load

Override full-load GPH (optional)

GPH

Estimated runtime

63.1 hours(2.6 days)

Fuel consumption ≈ 1.19 GPH at 75% load. Estimate based on industry-typical 1800 RPM standby curves (≈0.07 GPH/kW at full load). Actual consumption varies by engine, ambient temperature, fuel quality, and tuning.

Service intervals

Manufacturer-recommended intervals for the Atlas Copco QAS 25 under standby duty. Field intervals may differ based on load profile, ambient conditions, and fuel quality.

Oil & filter: Every 500 hours or 12 months
Air filter: Every 500 hours
Fuel filter: Every 500 hours
Major overhaul: ≈ 20,000 hours

Common failure modes

What we've seen fail on this platform. Use as a service-planning reference, not a diagnostic — actual failure modes depend heavily on duty cycle and maintenance history.

Component	Symptom	Typical hours	Severity
Fuel filter	Restricted fuel flow, hard starting, power loss	500+	minor
Starting battery	Failed start or slow cranking after extended storage	4,380+	minor
Coolant hoses	Weeping at clamp joints, low coolant warning	5,000+	minor

Frequently Asked Questions

What is the prime and standby rating of the Atlas Copco QAS 25?: The QAS 25 delivers 20 kW prime power and 22 kW standby power. Prime rating applies to continuous use with variable load; standby rating is for backup applications with an average load factor of 70%.
What engine does the Atlas Copco QAS 25 use?: The QAS 25 is powered by an Isuzu 4LE2T 2.2-liter inline-4 turbocharged diesel engine running at 1,800 RPM. The 4LE2T meets EPA Tier 4 Final emissions without a diesel particulate filter, using DOC aftertreatment only.
What are the service intervals for the QAS 25?: Oil changes are due every 500 hours or 12 months, whichever comes first. Air filter and fuel filter replacement intervals are 500 hours. Major engine overhaul is specified at 20,000 hours under normal operating conditions.
Is the Atlas Copco QAS 25 EPA Tier 4 Final compliant?: Yes. The QAS 25 is EPA Tier 4 Final and CARB compliant, making it legal for operation throughout California and all U.S. jurisdictions without restriction.
How does the QAS 25 differ from the larger QAS 45?: The QAS 45 uses the Isuzu 4LE2X variant (turbocharged and aftercooled) delivering 36 kW prime from the same 2.2-liter displacement. The QAS 25's 4LE2T is turbocharged only — no aftercooler. Both share the same 67 dBA noise level and 75-gallon fuel tank, but the QAS 45 adds 80% more prime power.
What fuel does the Atlas Copco QAS 25 use?: The QAS 25 runs on diesel fuel. The integral 75-gallon fuel tank provides over 48 hours of continuous runtime at 75% load. No diesel exhaust fluid (DEF) is required — the 4LE2T meets Tier 4 Final without SCR aftertreatment.
Who services Atlas Copco generators in Northern California?: OnPoint Generators provides local service and maintenance for Atlas Copco QAS units across the Bay Area and Northern California. We maintain familiarity with the full QAS lineup including the Isuzu-powered models and offer faster response times than the Atlas Copco factory service network.

Compatible equipment

Engine

Isuzu 4LE2TEngines

More in the QAS Series

Atlas Copco's portable diesel workhorse — 22 to 616 kW, Tier 4 Final, Leroy Somer alternators, 5–8 dB quieter than the competition.

View all 14models in this series →

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