Metric Horsepower to Kilowatts on Vehicle Documents

The PS You Bought and the Kilowatts on Your Registration Document

The showroom sold you a 150 PS car. Then the registration certificate arrives — a German Zulassungsbescheinigung, a UK V5C, a Certificate of Conformity from the importer — and the engine is described as 110 kW. Insurers, road-tax calculators and licence rules all work from that kilowatt entry, so it is worth being able to move between the two on sight.

Conversion factor: 1 PS = 0.73549875 kW — multiply the PS figure by 0.7355, or divide by 1.36 in your head. A 150 PS engine is 110.32 kW, which is why the document reads 110 kW.

Where the Kilowatt Entry Lives

Field P.2 on a German Fahrzeugschein

The Zulassungsbescheinigung Teil I carries rated power in field P.2, printed without a leading K and separated from the rated engine speed by a slash. No PS figure appears anywhere on the document.

Max net power on a V5C

The British logbook uses the same harmonised field code and labels it maximum net power in kW. It is the entry an insurer's proposal form and most online quote engines ask you to repeat.

The Certificate of Conformity

When a car is registered in another EU country, the COC supplies the official figures. Its maximum net power entry, in kilowatts, is what the registration office copies across — so a mistake there follows the car for life.

Why kilowatts won the paperwork

The kilowatt is the SI unit, so European type approval and every harmonised document are written in it. PS survived in advertising because buyers grew up with it, which leaves one engine carrying two numbers.

Checking a Brochure Number Against the Certificate

Most of the time you are doing one of two things: confirming the document describes the car you actually bought, or working out which band a tax or insurance rule puts you in.

Type the PS figure from the brochure

Enter 110, 150, 245 — whatever the price list quoted — and the kilowatt value builds as you type. European sources often write 110,3 with a comma, which the field reads as a decimal without complaint.

Compare it with the entry on the certificate

Documents are printed to whole kilowatts, so expect the official value to sit within a unit of your result. A difference of five or more usually means the car is a different engine variant from the one in the brochure you are reading.

Copy the kilowatt value into the calculator or quote form

The copy button gives you the digits alone — no unit, no thousands spacing — which is exactly what a tax calculator or an insurance quote field expects. Ctrl + C inside a field works the same way.

Read a document figure back into familiar terms

Looking at a used-car advert that only quotes the certificate value? Press the swap button (↔) for kW → PS. Multiplied by 1.3596, 85 kW turns back into 115.6 PS.

Rounding cuts both ways at a threshold: a rule written at 105 kW is applied to the whole number on the certificate, not to your converted decimal. A 143 PS car calculates to 105.18 kW and will be recorded as 105 — inside the limit — while 144 PS gives 105.91 and rounds the wrong way.

Power Thresholds European Rules Are Written In

Tax offices and licensing authorities set their limits in kilowatts. Here is what those thresholds look like next to the metric horsepower figure drivers actually recognise.

Threshold or typical rating	Kilowatts	In PS	Where you meet it
Italian new-driver ceiling for cars	105 kW	142.8 PS	Absolute cap for the first three years of a category B licence, in force since December 2024
Italian new-driver specific power	75 kW per tonne	102.0 PS/t	Power-to-weight limit applied over the same three-year period
The Italian cap before the reform	70 kW	95.2 PS	Older rule: 55 kW per tonne and 70 kW for one year
Austrian kilowatt deductible, 2020 registrations	65 kW	88.4 PS	Motor-related insurance tax charges only the kilowatts above it; the deductible drops a kilowatt each model year
Entry-level petrol hatchback	55 kW	74.8 PS	Comfortably inside every novice restriction on the list
Mid-range turbo family car	110 kW	149.6 PS	Just over the Italian ceiling — the classic disappointment for a first car
Hot hatch	180 kW	244.7 PS	High insurance power classes and a noticeably larger per-kilowatt tax bill
Six-cylinder performance saloon	250 kW	339.9 PS	The upper end of the range these national bands are drawn across

Two things stand out. First, the thresholds land on tidy kilowatt values and untidy PS ones, which is a reminder of which unit the rule was actually written in. Second, the difference between passing and failing a limit can be one engine option: a 150 PS version of the same model is 110.3 kW and out of reach of an Italian licence holder in year two, while the 136 PS variant at 100.0 kW is fine.

Useful Behaviour When You Have the Logbook Open

Type in whichever unit the page in front of you uses

Both fields accept input and update each other, so you can jump between a price list in PS and a certificate in kW without touching a reset button.

Turn a document entry back into the showroom figure

The swap arrows run kW → PS, which is the direction you want when a used-car advert quotes only what the registration paper says.

Horsepower is one dropdown away

Searchable unit lists on both sides include mechanical horsepower, so a figure from an English-language review joins the same comparison as the certificate value.

Decimals that decide a borderline case

Up to eight decimal places are shown, which matters when a car sits within a kilowatt of a tax or licence threshold and you need to see which side of it the arithmetic falls.

Registration and Road Tax Questions

Why does my registration document show kW when the brochure said PS?

Because vehicle documents follow European type approval, which is written in SI units, and the fields are harmonised so that any member state's authority can read another's paperwork. Metric horsepower has no legal standing there — it survives only in advertising and conversation. Your car has not been re-rated; 150 PS and 110 kW are the same engine described twice.

Do European road taxes really charge by the kilowatt?

Some do, directly. Austria's motor-related insurance tax works from the kilowatt figure with a deductible — 65 kW for cars first registered in 2020, falling by one kilowatt each year — plus a carbon dioxide component, and is charged monthly. Others use power indirectly: several countries set annual bands by engine power, and France derives an administrative horsepower class used for registration fees. Germany is the outlier for cars, taxing displacement and emissions instead. Whichever system applies, the kilowatt entry on the certificate is the input.

How does the Italian new-driver power limit translate into PS?

Since 14 December 2024 a category B licence holder may not drive an M1 car above 105 kW, or above 75 kW per tonne of kerb weight, for three years from the date the licence was issued. That absolute cap is 142.8 PS, and the ratio works out at 102.0 PS per tonne. The earlier rule was tighter but shorter: 70 kW — 95.2 PS — and 55 kW per tonne for a single year.

Is the kilowatt figure the maximum power or a rated figure?

It is the rated net power measured under the European type-approval procedure for engine power, with the engine complete and driving its own ancillaries. For a combustion car it is effectively peak output. For an electric one the same field is meant to hold the highest 30-minute power — a continuous rating — so it can sit well below the peak number the marketing material shouts about.

Which kilowatt figure applies to a hybrid?

The type-approval procedure measures a combustion engine and an electric machine separately; it does not define a single combined output for a hybrid drivetrain. Manufacturers publish a system figure of their own, usually lower than the two components added together because the battery cannot always feed the motor at full engine load. The result is that a plug-in hybrid's certificate can list a kilowatt value that matches neither the engine alone nor the system PS in the brochure — so check which one a tax rule or insurance question is asking for.

Metric Horsepower to Kilowatts