What is power and how is it measured?

Power is the rate of energy transfer per unit time. SI unit is the watt (W): 1 W = 1 joule per second. Mechanical, electrical, and thermal power can all be expressed in watts.

How do I convert between watts and horsepower?

1 mechanical hp = 745.7 W. So watts ÷ 745.7 = hp; hp × 745.7 = watts. Example: 1,000 W ≈ 1.34 hp; 2 hp = 1,491 W.

What's the difference between power and energy?

Power (W, kW) is rate; energy (Wh, kWh, J) is total over time. A 100 W bulb uses 100 W of power and 0.1 kWh of energy per hour.

How do I convert BTU/h to watts?

Multiply BTU/h by 0.293071 to get watts. So 3,412 BTU/h = 1 kW. Example: 12,000 BTU/h AC ≈ 3.52 kW.

What are common power units by industry?

Appliances and grid: W, kW, MW. Cars: hp (US/UK) or PS (Europe). HVAC: BTU/h (US) or W/kW. This converter supports all of them.

How accurate is this power converter?

Factors follow NIST: 1 hp = 745.7 W, 1 BTU/h = 0.293071 W, 1 PS = 735.5 W. Suitable for engineering and sizing.

Power Converter

Car engines are rated in horsepower; space heaters in watts or BTU per hour. Power is how fast energy is used — a 100 W bulb uses 100 joules every second. Mixing hp, kW, and BTU/h leads to wrong sizing for motors, HVAC, or solar.

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Quick Reference: Most Searched Power Conversions

1 hp in kWMost searched

0.746 kW

1 kW in hpMotors

1.34 hp

1000 W in BTU/hHVAC

3,412 BTU/h

12,000 BTU/h in kWAC unit

3.52 kW

1 hp in wattsExact

746 W

100 W in BTU/hHeater

341 BTU/h

1 metric hp (PS) in kWEU cars

0.736 kW

5 kW in hpSmall engine

6.71 hp

Real-World Power Scale

How these numbers relate to everyday life

1 watt

SI unit. A small LED may use 0.5–2 W; phone charger idle ~0.1 W.

15W

Laptop (typical)

Average draw under load; charging can be 45–65 W for many models.

100W

Incandescent bulb (old)

Classic 100 W bulb; LED equivalent is ~10–15 W for same light.

746W

1 mechanical horsepower

James Watt defined hp as the work of one horse; 1 hp ≈ 746 W.

1,500W

Space heater (small)

Common 1.5 kW plug-in heater; 1,500 W = 5,118 BTU/h.

3,500W

Window AC (12,000 BTU/h)

12,000 BTU/h ≈ 3.52 kW cooling; input power often 3–4 kW.

7,355W

10 metric hp (PS)

European car power: 1 PS = 735.5 W. 100 PS ≈ 73.6 kW.

74,570W

100 hp engine

Small car engine; 100 hp = 74.6 kW. Family sedan often 150–200 hp.

1,000,000W

1 MW

Industrial scale. A 1 MW turbine can power hundreds of homes at once.

Who Uses Power Conversions?

Automotive & Motors

US and UK use mechanical horsepower (hp); Europe uses metric horsepower (PS). Electric motors and specs are often in kW. Wrong unit leads to under- or over-estimating output.

150 hp = 112 kW. 100 PS = 73.6 kW. A 2.0 L turbo might be 250 hp = 186 kW.

HVAC & Appliances

Heaters and AC are labeled in BTU/h in the US and in watts or kW elsewhere. Sizing a room requires the same unit for load and equipment rating.

12,000 BTU/h = 3.52 kW. A 1,500 W heater = 5,118 BTU/h. Room need 5 kW → ~17,000 BTU/h.

Solar & Grid

Solar panels are rated in watts (Wp); inverters and consumption in kW or MW. Utility scale is GW. Converting avoids mismatches between capacity and demand.

10 kW rooftop array = 10,000 W. 1 GW power plant = 1,000 MW. Average US home draw ~1.2 kW.

Cycling & Fitness

Power meters on bikes report watts. Training zones and comparisons (e.g. pro cyclists) use W or W/kg. Horsepower is rarely used but appears in some legacy specs.

Pro cyclist FTP ~400 W. Amateur 200–250 W. 1 hp = 746 W so 0.5 hp ≈ 373 W sustained.

Industrial Machinery

Pumps, compressors, and machine tools are specified in hp (US) or kW (metric). Motor nameplates may show both; conversion ensures correct replacement or sizing.

5 hp motor = 3.73 kW. A 15 kW motor = 20.1 hp. Derating for altitude or temperature uses same power unit.

Did You Know?

James Watt defined horsepower by observing draft horses at a coal mine: one horse could do about 33,000 foot-pounds of work per minute, which he rounded to 550 ft·lbf/s — today that is 745.7 W.

Source: Historical (Watt, 18th century)

Metric horsepower (PS, from the German Pferdestärke) is slightly less than mechanical hp: 1 PS = 735.5 W vs 1 hp = 745.7 W. European car brochures often quote PS.

Source: DIN 66036

BTU per hour (BTU/h) is power, not energy. A 10,000 BTU/h AC removes 10,000 BTU of heat each hour. 1 W = 3.412 BTU/h; so 1 kW = 3,412 BTU/h.

Source: NIST

Common Mistakes to Avoid

Confusing energy (kWh) with power (kW) when sizing equipment

Power (kW) is rate; energy (kWh) is total over time. A 5 kW heater running 2 hours uses 10 kWh. Size the heater by power (kW or BTU/h), not by energy.

Using mechanical hp and metric hp (PS) as if they were the same

1 hp (mechanical) = 745.7 W. 1 PS (metric) = 735.5 W. A 100 PS car has 73.6 kW; 100 hp (mech) is 74.6 kW. Difference is about 1.4%.

Treating BTU/h and BTU as the same

BTU is energy; BTU/h is power. A 24,000 BTU/h furnace delivers 24,000 BTU of heat per hour. 24,000 BTU (energy) would be the heat content of a small amount of fuel, not the furnace output rate.