HP vs kW Motor Ratings on Blowers Explained

To convert horsepower to kilowatts, multiply by 0.7457. To convert kW to HP, multiply by 1.341. A 5 HP motor is 3.73 kW; a 4 kW motor is 5.36 HP. Yash blowers are labelled in HP on the side-channel range and in kW on the dry-vacuum range, so anyone comparing across the catalogue — or against an electricity bill in kW — has to move between the two. This guide gives the exact factor and, more usefully, explains what the number on the nameplate actually means.

For the airflow and pressure sides of the same selection, see the CFM to m³/hr guide and the mbar to PSI guide.

The exact power factor

The mechanical horsepower is defined as 550 foot-pounds per second, which works out to:

• 1 HP = 0.745700 kW (745.7 W)
• 1 kW = 1.34102 HP

Note the last row: metric horsepower (PS) is 0.7355 kW, slightly smaller than mechanical HP. European and some Chinese datasheets occasionally quote PS. When the difference matters — motor procurement, VFD sizing — confirm which HP is meant. Yash uses mechanical HP (0.7457). The /tools/unit-converter has both.

Worked examples on real Yash models

Yash prints power in both conventions across families. Here they reconcile:

The dry-vacuum YBDVP 160 at 5.5 kW is a 7.5 HP-class machine — obvious once converted, easy to misjudge if you compare "5.5" against a blower's "5.0 HP" without doing the maths.

Input power vs output power: the number that actually costs money

Here is the distinction most sizing goes wrong on. The nameplate HP/kW is the motor's rated shaft output — the mechanical power it can deliver. It is not what the motor draws from the wall. Electrical input power is higher, because the motor is not 100% efficient:

• Input power (kW) = Output (kW) ÷ motor efficiency

A 5 HP (3.73 kW output) motor at 88% efficiency draws about 4.24 kW electrical. Over a year of continuous running that gap is real money.

Run your own duty hours and tariff through the /tools/energy-savings-calculator — it uses input power, not nameplate, which is the honest basis for comparing two blowers.

Actual absorbed power is often below nameplate

A blower does not always load its motor to full rating. A side-channel blower running at part of its pressure curve may absorb noticeably less than nameplate. That is why measured amps at the duty point matter more than the label for energy estimates. But you size the motor for the worst case (highest pressure, cold dense air, blocked filter drift), which is why nameplate exists.

Service factor and why the motor is "oversized"

Indian industrial motors typically carry a service factor of 1.0 to 1.15. A 1.15 service factor means the motor can run continuously at 15% above rated output without overheating — headroom for voltage dips, high ambient, and dirty-filter drift. This is a feature, not waste. When a blower's absorbed power creeps up because an inlet filter is clogging, that margin is what keeps the motor alive until maintenance. Keep the air filter serviced and you rarely dip into it.

Service factor also explains why you should not "right-size" a motor to zero margin off a spreadsheet. Ambient in Faridabad hits 45 °C+ in summer; a motor rated at 40 °C ambient derates above that. The margin absorbs it.

Reading a nameplate correctly

A blower motor nameplate carries more than HP/kW. What to check:

Frequency is the sleeper: a 60 Hz-labelled motor run on India's 50 Hz spins 17% slower, so a side-channel blower delivers less flow and pressure. If you import a machine, confirm 50 Hz. This is also why VFD minimum-frequency limits matter for cooling — covered in the VFD with ring blowers guide.

Quick-reference power table

Efficiency class beats rated power for running cost

Two 5 HP motors are not equal. The efficiency class — IE2, IE3, IE4 under the international scheme — decides how much of the electricity you pay for becomes shaft power and how much becomes waste heat. On a blower running long hours, the class matters more to the bill than the rated power does.

Worked comparison, 5 HP (3.73 kW output) at 24/7:

• At 88% efficiency, input ≈ 4.24 kW → ~37,100 kWh/year.
• At 91% efficiency, input ≈ 4.10 kW → ~35,900 kWh/year.

That 3-point efficiency gain saves ~1,200 kWh a year on one blower — real money over a fleet, every year, for the machine's whole life. The higher-class motor usually costs a little more up front and pays it back quickly on continuous duty. Feed your duty hours and tariff into the /tools/energy-savings-calculator to see the payback for your case.

Why you cannot compare motors on HP alone

This is the practical takeaway from the conversion: HP (or kW) tells you the capacity, not the cost. Two blowers quoted "5 HP" can differ 5-8% in electricity use depending on motor class and how hard the blower actually loads the motor at your duty point. When comparing suppliers, ask for the efficiency class and the absorbed power at your duty, not just the nameplate rating. A cheaper blower with a lower-class motor can cost more over three years than a dearer one with an IE3 motor — the energy calculator makes that visible.

Match the motor to the real duty

Nameplate HP is the start, not the answer. Send us your duty — flow, pressure, ambient, supply voltage and phase — and we will confirm the right Yash model, its true absorbed power, and whether your supply can carry the start current.

• WhatsApp: +91 9311693322
• Email: sales@yashblowers.org

Yash Blowers, building blowers and vacuum pumps in Faridabad since 1998. We will tell you what the motor draws, not just what the label says.