How to Read an Engine Nameplate & Spec Sheet

Two documents tell you everything about a generator engine: the nameplate bolted to the engine, and the spec sheet (data sheet) that comes with it. The nameplate identifies the exact unit in front of you; the spec sheet tells you what it can do. Once you can read both, buying, servicing and matching an engine gets a lot easier.

The short version: the nameplate gives the model, serial number, rated power and emission certification of that specific engine. The spec sheet gives the full performance picture — prime and standby power at 50/60 Hz, displacement, cylinders, speed and more.

Part 1 — The nameplate (data plate)

The nameplate is the metal plate fixed to the engine block. It's the engine's identity card: you need it for ordering parts, validating warranty, and proving emissions compliance. Here's how the fields break down — the photo above is a real Perkins 404D-22 plate.

• Engine model (404D-22) — the manufacturer's model. Perkins's code even encodes the engine: 4 cylinders, D for diesel, 2.2 litres.
• Serial number (GN71039R085563L) — unique to this one engine. Quote it for spare parts and warranty.
• Rated power (24.3 kW) — the engine's rated mechanical output. Note this is engine kW, not the genset's electrical kWe (see kVA vs kW).
• Displacement (2.22 L) — total swept volume of the cylinders.
• EPA engine family (TPKXL02.2NLC) — the EPA certification family that groups engines of the same emissions design.
• Build date (Oct 2025) — when it was manufactured.
• Emission standard — here, "conforms to 2026 U.S. EPA regulations for stationary compression-ignition engines," flagged for emergency use only (with a California-specific note). This tells you where and how the engine is legal to run — see EPA emission standards.
• Approved fuel — "commercially available diesel fuel."

The plate's wording matters: "stationary emergency use only" or "not for non-road mobile machinery" defines the legal application. Installing an engine outside its certified use can carry penalties.

Part 2 — The spec sheet (data sheet)

The spec sheet is the document that describes what the engine can do. The most important section is the power ratings, which is also the most misread.

Power ratings

A genset spec sheet usually lists several numbers per frequency:

Term	Meaning
kWm	Mechanical power at the engine flywheel
kWe	Electrical power after alternator/fan losses
kVA	Apparent power (kWe ÷ 0.8 power factor)
Prime (PRP)	Unlimited-hours rating for a variable load
Standby (ESP)	Backup-only rating (~200 h/year), usually ~10% higher
50 Hz / 60 Hz	1,500 rpm vs 1,800 rpm (for a 4-pole set)

So "500 kVA standby / 400 kWe prime at 50 Hz" is four facts in one line. If you're unsure which to use, see prime vs standby and kVA vs kW.

Watch for the basis: ratings may be quoted net (with fan) or gross, which changes the number — always compare like with like.

Engine and performance data

The rest of the sheet describes the hardware:

• Cylinders & configuration — e.g. inline-6 (L6) or V12.
• Bore × stroke, displacement and compression ratio.
• Aspiration — naturally aspirated, turbocharged, or turbo + intercooled.
• Cooling — liquid- or air-cooled (see air vs water cooling).
• Rated speed — the rpm, which pins the frequency (1,500 = 50 Hz, 1,800 = 60 Hz).
• Fuel consumption — usually litres/hour at several load points.
• Emission standard — e.g. U.S. EPA Tier, EU Stage V, or China stage.
• Weight and dimensions of the engine (or the genset).

Putting it together

Use the nameplate to confirm exactly what you have (and that it's certified for your application), and the spec sheet to confirm it does what you need:

1. Model + serial → identify and order parts.
2. Emission line → check it's legal where you'll run it.
3. Power ratings → match prime/standby kWe & kVA to your load.
4. Speed/frequency → match your grid (50 or 60 Hz).
5. Cooling, weight, dimensions → check it fits the installation.

Every engine page in this catalogue lays these out the same way — power ratings, displacement, cylinders, cooling and emissions — and links the manufacturer's spec sheet where available.

Next steps

Brush up on kVA vs kW and prime vs standby, then browse the engine catalogue and read a few spec pages with this guide open.