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Power-to-weight ratio (or specific power or power-to-mass ratio) is a calculation commonly applied to engines and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measurement of actual performance of any engine or power source. It is also used as a measurement of performance of a vehicle as a whole, with the engine's power output being divided by the weight (or mass) of the vehicle, to give a metric that is independent of the vehicle's size. Power-to-weight is often quoted by manufacturers at the peak value, but the actual value may vary in use and variations will affect performance.

The inverse of power-to-weight, weight-to-power ratio (power loading) is a calculation commonly applied to aircraft, cars, and vehicles in general, to enable the comparison of one vehicle's performance to another. Power-to-weight ratio is equal to thrust per unit mass multiplied by the velocity of any vehicle.

Power-to-weight (specific power)

The power-to-weight ratio (Specific Power) formula for an engine (power plant) is the power generated by the engine divided by the mass. ("Weight" in this context is a colloquial term for "mass". To see this, note that what an engineer means by the "power to weight ratio" of an electric motor is not infinite in a zero gravity environment.)

A typical turbocharged V8 diesel engine might have an engine power of Template:Convert and a mass of Template:Convert, giving it a power-to-weight ratio of 0.65 kW/kg (0.40 hp/lb).

Examples of high power-to-weight ratios can often be found in turbines. This is because of their ability to operate at very high speeds. For example, the Space Shuttle's main engines used turbopumps (machines consisting of a pump driven by a turbine engine) to feed the propellants (liquid oxygen and liquid hydrogen) into the engine's combustion chamber. The original liquid hydrogen turbopump is similar in size to an automobile engine (weighing approximately Template:Convert) and produces 72,000 hp (53.6 MW) for a power-to-weight ratio of 153 kW/kg (93 hp/lb).

Physical interpretation

In classical mechanics, instantaneous power is the limiting value of the average work done per unit time as the time interval Δt approaches zero.

$P=\underset{\mathrm{\Delta }t\to 0}{\lim }\frac{\mathrm{\Delta }W(t)}{\mathrm{\Delta }t}=\underset{\mathrm{\Delta }t\to 0}{\lim }{P}_{\mathrm{a}\mathrm{v}\mathrm{g}}$

The typically used metrical unit of the power-to-weight ratio is $\frac{W}{kg}$ which equals $\frac{m^2}{s^3}$. This fact allows one to express the power-to-weight ratio purely by SI base units.

Propulsive power

If the work to be done is rectilinear motion of a body with constant mass $m$, whose center of mass is to be accelerated along a straight line to a speed $|\mathbf{v}(t)|$ and angle $\varphi$ with respect to the centre and radial of a gravitational field by an onboard powerplant, then the associated kinetic energy to be delivered to the body is equal to

$E_K=\frac{1}{2}m|\mathbf{v}(t){|}^2$

where:

$m$ is mass of the body

$|\mathbf{v}(t)|$ is speed of the center of mass of the body, changing with time.

The instantaneous mechanical pushing/pulling power delivered to the body from the powerplant is then

$P_K=\frac{1}{2}m2|\mathbf{v}(t)|\underset{\mathrm{\Delta }t\to 0}{\lim }\frac{\mathrm{\Delta }|\mathbf{v}(t)|}{\mathrm{\Delta }t}=m\mathbf{a}(t)\cdot \mathbf{v}(t)=\mathbf{F}(t)\cdot \mathbf{v}(t)=\mathit{\tau }(t)\cdot \mathit{\omega }(t)$

where:

$\mathbf{a}(t)$ is acceleration of the center of mass of the body, changing with time.

$\mathbf{F}(t)$ is linear force - or thrust - applied upon the center of mass of the body, changing with time.

$\mathbf{v}(t)$ is velocity of the center of mass of the body, changing with time.

$\mathit{\tau }(t)$ is torque applied upon the center of mass of the body, changing with time.

$\mathit{\omega }(t)$ is angular velocity of the center of mass of the body, changing with time.

In propulsion, power is only delivered if the powerplant is in motion, and is transmitted to cause the body to be in motion. It is typically assumed here that mechanical transmission allows the powerplant to operate at peak output power. This assumption allows engine tuning to trade power band width and engine mass for transmission complexity and mass. Electric motors do not suffer from this tradeoff, instead trading their high torque for traction at low speed. The power advantage or power-to-weight ratio is then

$\text{P-to-W}=\frac{|\mathbf{a}(t)||\mathbf{v}(t)|}{\left|\mathbf{g}\right|}$

where:

$|\mathbf{v}(t)|$ is linear speed of the center of mass of the body.

Engine power

The actual useful power of any traction engine can be calculated using a dynamometer to measure torque and rotational speed, with peak power sustained when transmission and/or operator keeps the product of torque and rotational speed maximised. For jet engines there is often a cruise speed and power can be usefully calculated there, for rockets there is typically no cruise speed, so it is less meaningful.

Peak power of a traction engine occurs at a rotational speed higher than the speed when torque is maximised and at or below the maximum rated rotational speed - Max RPM. A rapidly falling torque curve would correspond with sharp torque and power curve peaks around their maxima at similar rotational speed, for example a small, lightweight engine with a large turbocharger. A slowly falling or near flat torque curve would correspond with a slowly rising power curve up to a maximum at a rotational speed close to Max RPM, for example a large, heavy multi-cylinder engine suitable for cargo/hauling. A falling torque curve could correspond with a near flat power curve across rotational speeds for smooth handling at different vehicle speeds.

Examples

Engines

Heat engines and heat pumps

Thermal energy is made up from molecular kinetic energy and latent phase energy. Heat engines are able to convert thermal energy in the form of a temperature gradient between a hot source and a cold sink into other desirable mechanical work. Heat pumps take mechanical work to regenerate thermal energy in a temperature gradient. Care should be made when interpreting propulsive power, especially for jet engines and rockets, deliverable from heat engines to a vehicle.

Heat Engine/Heat pump type	Peak Power Output		Power-to-weight ratio		Example Use
Wärtsilä RTA96-C 14-cylinder two-stroke Turbo Diesel engine	80,080 kW	108,920 hp	0.03 kW/kg	0.02 hp/lb	Emma Mærsk container ship
Suzuki 538 cc V2 4-stroke gas (petrol) outboard Otto engine	19 kW	25 hp	0.27 kW/kg	0.16 hp/lb	Runabout boats
DOE/NASA/0032-28 Mod 2 502 cc gas (petrol) Stirling engine	62.3 kW	83.5 hp	0.30 kW/kg	0.18 hp/lb	Chevrolet CelebrityTemplate:Cref2 1985
GM 6.6 L Duramax LMM (LYE option) V8 Turbo Diesel engine	246 kW	330 hp	0.65 kW/kg	0.40 hp/lb	Chevrolet KodiakTemplate:Cref2, GMC TopkickTemplate:Cref2
Junkers Jumo 205A opposed-piston two-stroke Diesel engine	647 kW	867 hp	1.1 kW/kg	0.66 hp/lb	Ju 86C-1 airliner, B&V Ha 139 floatplane
GE LM2500+ marine turboshaft Brayton gas turbine	30,200 kW	40,500 hp	1.31 kW/kg	0.80 hp/lb	GTS Millennium cruiseship, QM2 ocean liner
Mazda 13B-MSP Renesis 1.3 L Wankel engine	184 kW	247 hp	1.5 kW/kg	0.92 hp/lb	Mazda RX-8Template:Cref2
PW R-4360 71.5 L 28-cylinder supercharged Radial engine	3,210 kW	4,300 hp	1.83 kW/kg	1.11 hp/lb	B-50 Superfortress, Convair B-36
					C-97 Stratofreighter, C-119 Flying Boxcar
					Hughes H-4 Hercules "Spruce Goose"
Wright R-3350 54.57 L 18-c s/c Turbo-compound Radial engine	2,535 kW	3,400 hp	2.09 kW/kg	1.27 hp/lb	B-29 Superfortress, Douglas DC-7
					C-97 S/f prototype, Kaiser-Frazer C-119F
O.S. Engines 49-PI Type II 4.97 cc UAV Wankel engine	0.934 kW	1.252 hp	2.8 kW/kg	1.7 hp/lb	Model aircraft, Radio-controlled aircraft
GE LM6000 marine turboshaft Brayton gas turbineTemplate:Disputed-inline	44,700 kW	59,900 hp	5.67 kW/kg	3.38 hp/lb	Peaking power plant
GE CF6-80C2 Brayton high-bypass turbofan jet engine					Boeing 747Template:Cref2, 767, Airbus A300
BMW V10 3L P84/5 2005 gas (petrol) Otto engine	690 kW	925 hp	7.5 kW/kg	4.6 hp/lb	Williams FW27 carTemplate:Cref2, Formula One auto racing
GE90-115B Brayton turbofan jet engineTemplate:Disputed-inline	83,164 kW	111,526 hp	10.0 kW/kg	6.10 hp/lb	Boeing 777
PWR RS-24 (SSME) Block II H2 Brayton turbopump	63,384 kW	85,000 hp	138 kW/kg	84 hp/lb	Space Shuttle (STS-110 and later) Template:Cref2
PWR RS-24 (SSME) Block I H2 Brayton turbopump	53,690 kW	72,000 hp	153 kW/kg	93 hp/lb	Space Shuttle

Electric motors/Electromotive generators

An electric motor uses electrical energy to provide mechanical work, usually through the interaction of a magnetic field and current-carrying conductors. By the interaction of mechanical work on an electrical conductor in a magnetic field, electrical energy can be generated.

Electric motor type	Weight		Peak Power Output		Power-to-weight ratio		Example Use
Panasonic MSMA202S1G AC servo motor	6.5 kg	14.3 lb	2 kW	2.7 hp	0.31 kW/kg	0.19 hp/lb	Conveyor belts, Robotics
Toshiba 660 MVA water cooled 23kV AC turbo generator	1,342 t	2,959,000 lb	660 MW	885,000 hp	0.49 kW/kg	0.30 hp/lb	Bayswater, Eraring Coal Power stations
Canopy Tech. Cypress 32 MW 15 kV AC PM generator	33,557 kg	73,981 lb	32 MW	42,913 hp	0.95 kW/kg	0.58 hp/lb	Electric Power stations
Toyota Brushless AC Nd Fe B PM motor	36.3 kg	80.0 lb	50 kW	67 hp	1.37 kW/kg	0.84 hp/lb	Toyota PriusTemplate:Cref2 2004
Himax HC6332-250 Brushless DC motor	0.45 kg	0.99 lb	1.7 kW	2.28 hp	3.78 kW/kg	2.30 hp/lb	Radio controlled cars
Hi-Pa Drive HPD40 Brushless DC wheel hub motor	25 kg	55.1 lb	120 kW	161 hp	4.8 kW/kg	2.92 hp/lb	Mini QED HEV, Ford F150 HEV
ElectriFly GPMG4805 Brushless DC	1.48 kg	3.26 lb	8.4 kW	11.26 hp	5.68 kW/kg	3.45 hp/lb	Radio-controlled aircraft
EMRAX228 Brushless AC electric Motor	11.9 kg	26.18 lb	100 kW	134 hp	8.4 kW/kg	5.12 hp/lb	Battery Electric Air Plane

Fluid engines and fluid pumps

Fluids (liquid and gas) can be used to transmit and/or store energy using pressure and other fluid properties. Hydraulic (liquid) and pneumatic (gas) engines convert fluid pressure into other desirable mechanical or electrical work. Fluid pumps convert mechanical or electrical work into movement or pressure changes of a fluid, or storage in a pressure vessel.

Fluid Powerplant type	Dry Weight		Peak Power Output		Power-to-weight ratio
PlatypusPower Q2/200 hydroelectric turbine	43 kg	95 lb	2 kW	2.7 hp	0.047 kW/kg	0.029 hp/lb
PlatypusPower PP20/200 hydroelectric turbine	330 kg	728 lb	20 kW	27 hp	0.060 kW/kg	0.037 hp/lb
Atlas Copco LZL 35 pneumatic motor	20 kg	44.1 lb	6.5 kW	8.7 hp	0.33 kW/kg	0.20 hp/lb
Atlas Copco LZB 14 pneumatic motor	0.30 kg	0.66 lb	0.16 kW	0.22 hp	0.53 kW/kg	0.33 hp/lb
Bosch 0 607 954 307 pneumatic motor	0.32 kg	0.71 lb	0.1 kW	0.13 hp	0.31 kW/kg	0.19 hp/lb
Atlas Copco LZB 46 pneumatic motor	1.2 kg	2.65 lb	0.84 kW	1.13 hp	0.7 kW/kg	0.43 hp/lb
Bosch 0 607 957 307 pneumatic motor	1.7 kg	3.7 lb	0.74 kW	0.99 hp	0.44 kW/kg	0.26 hp/lb
SAI GM7 radial piston hydraulic motor	300 kg	661 lb	250 kW	335 hp	0.83 kW/kg	0.50 hp/lb
SAI GM3 radial piston hydraulic motor	15 kg	33 lb	15 kW	20 hp	1 kW/kg	0.61 hp/lb
Denison GOLD CUP P14 axial piston hydraulic motor	110 kg	250 lb	384 kW	509 hp	3.5 kW/kg	2.0 hp/lb
Denison TB vane pump	7 kg	15 lb	40.2 kW	53.9 hp	5.7 kW/kg	3.6 hp/lb

Thermoelectric generators and electrothermal actuators

A variety of effects can be harnessed to produce thermoelectricity, thermionic emission, pyroelectricity and piezoelectricity. Electrical resistance and ferromagnetism of materials can be harnessed to generate thermoacoustic energy from an electric current.

Thermoelectric Powerplant type	Dry Weight		Peak Power Output		Power-to-weight ratio		Example Use
Teledyne 238Pu GPHS-RTG 1980	56 kg	123 lb	285 W	0.39 hp	5.09 W/kg	0.003 hp/lb	Galileo probe, New Horizons probe
Boeing 238Pu MMRTG MSL	44.1 kg	97.2 lb	123 W	0.16 hp	2.79 W/kg	0.002 hp/lb	Mars Science Laboratory
HZ-20 thermoelectric module	0.115 kg	0.254 lb	19 W	0.025 hp	165 W/kg	0.098 hp/lb	Hi-Z Technology Inc.

Electrochemical (galvanic) and electrostatic cell systems

(Closed cell) batteries

All electrochemical cell batteries deliver a changing voltage as their chemistry changes from "charged" to "discharged". A nominal output voltage and a cutoff voltage are typically specified for a battery by its manufacturer. The output voltage falls to the cutoff voltage when the battery becomes "discharged". The nominal output voltage is always less than the open-circuit voltage produced when the battery is "charged". The temperature of a battery can affect the power it can deliver, where lower temperatures reduce power. Total energy delivered from a single charge cycle is affected by both the battery temperature and the power it delivers. If the temperature lowers or the power demand increases, the total energy delivered at the point of "discharge" is also reduced.

Battery discharge profiles are often described in terms of a factor of battery capacity. For example a battery with a nominal capacity quoted in ampere-hours (Ah) at a C/10 rated discharge current (derived in amperes) may safely provide a higher discharge current - and therefore higher power-to-weight ratio - but only with a lower energy capacity. Power-to-weight ratio for batteries is therefore less meaningful without reference to corresponding energy-to-weight ratio and cell temperature. This relationship is known as Peukert's law.

Battery type	Volts	Temp.	Energy-to-weight ratio	Power-to-weight ratio
Energizer 675 Mercury Free Zinc-air battery	1.4V	21 °C	1,645 kJ/kg to 0.9 V	1.65 W/kg 2.24 mA
GE Durathon™ NaMx A2 UPS Molten salt battery	54.2V	-40–65°C	342 kJ/kg to 37.8 V	15.8 W/kg C/6 (76 A)
Panasonic R03 AAA Zinc–carbon battery	1.5 V	20±2 °C	47 kJ/kg 20 mA to 0.9 V	3.3 W/kg 20 mA
			88 kJ/kg 150 mA to 0.9 V	24 W/kg 150 mA
Eagle-Picher SAR-10081 60Ah 22-cell Nickel–hydrogen battery	27.7 V	10 °C	192 kJ/kg C/2 to 22 V	23 W/kg C/2
			165 kJ/kg C/1 to 22 V	46 W/kg C/1
ClaytonPower 400Ah Lithium-ion battery	12V		617 kJ/kg	85.7 W/kg C/1 (175 A)
Energizer 522 Prismatic Zn–MnO2 Alkaline battery	9 V	21 °C	444 kJ/kg 25 mA to 4.8 V	4.9 W/kg 25 mA
			340 kJ/kg 100 mA to 4.8 V	19.7 W/kg 100 mA
			221 kJ/kg 500 mA to 4.8 V	99 W/kg 500 mA
Panasonic HHR900D 9.25Ah Nickel–metal hydride battery	1.2 V	20 °C	209.65 kJ/kg to 0.7 V	11.7 W/kg C/5
				58.2 W/kg C/1
				116 W/kg 2C
URI 1418Ah replaceable anode Aluminium–air battery model	244.8 V	60 °C	4680 kJ/kg	130.3 W/kg (142 A)
LG Chemical/CPI E2 6Ah LiMn2O4 Lithium-ion polymer battery	3.8 V	25 °C	530.1 kJ/kg C/2 to 3.0 V	71.25 W/kg
			513 kJ/kg 1C to 3.0 V	142.5 W/kg
Saft 45E Fe Super-Phosphate Lithium iron phosphate battery	3.3 V	25 °C	581 kJ/kg C to 2.5 V	161 W/kg
			560 kJ/kg 1.14 C to 2.0 V	183 W/kg
			0.73 kJ/kg 2.27 C to 1.5 V	367 W/kg
Energizer CH35 C 1.8Ah Nickel–cadmium battery	1.2 V	21 °C	152 kJ/kg C/10 to 1 V	4 W/kg C/10
			147.1 kJ/kg 5C to 1 V	200 W/kg 5 C
Firefly Energy Oasis FF12D1-G31 6-cell 105Ah VRLA battery	12 V	25 °C	142 kJ/kg C/10 to 7.2 V	4 W/kg C/10
		-1 8 °C	7 kJ/kg CCA to 7.2V	234 W/kg CCA (625A)
		0 °C	9 kJ/kg CA to 7.2 V	300 W/kg CA (800 A)
Panasonic CGA103450A 1.95Ah LiCoO2 Lithium-ion battery	3.7 V	20 °C	666 kJ/kg C/5.3 to 2.75 V	35 W/kg C/5.3
		0 °C	633 kJ/kg C/1 to 2.75 V	176 W/kg C/1
		20 °C	655 kJ/kg C/1 to 2.75 V	182 W/kg C/1
		20 °C	641 kJ/kg 2C to 2.75 V	356 W/kg 2C
Electric Fuel Battery Corp. UUV 120Ah Zinc–air fuel cell			630 kJ/kg	500 W/kg C/1
Sion Power 2.5Ah Li–S Lithium-ion battery	2.15 V	25 °C	1260 kJ/kg	70 W/kg C/5
			1209 kJ/kg	672 W/kg 2C
Maxell / Yuasa / AIST Nickel–metal hydride lab prototype		45 °C		980 W/kg
Toshiba SCiB cell 4.2Ah Li2TiO3 Lithium-ion battery	2.4 V	25 °C	242 kJ/kg	67.2 W/kg C/1
			218 kJ/kg	4000 W/kg 12C
Ionix Power Systems LiMn2O4 Lithium-ion battery lab model		lab	270 kJ/kg	1700 W/kg
		lab	29 kJ/kg	4900 W/kg
A123 Systems 26650 Cell 2.3Ah LiFePO4 Lithium ion battery	3.3 V	-20 °C	347 kJ/kg C/1 to 2V	108 W/kg C/1
		0 °C	371 kJ/kg C/1 to 2 V	108 W/kg C/1
		25 °C	390 kJ/kg C/1 to 2 V	108 W/kg C/1
		25 °C	390 kJ/kg 27C to 2 V	3300 W/kg 27C
		25 °C	57 kJ/kg 32C to 2 V	5657 W/kg 32C
Saft VL 6Ah Lithium-ion battery	3.65 V	-20 °C	154 kJ/kg 30C to 2.5 V	41.4 W/kg 30C (180 A)
			182 kJ/kg 1C to 2.5 V	67.4 W/kg 1C
		25 °C	232 kJ/kg 1C to 2.5 V	64.4 W/kg 1C
			233 kJ/kg 58.3C to 2.5 V	3757 W/kg 58.3C (350A)
			34 kJ/kg 267C to 2.5 V	17176 W/kg 267C (1.6kA)
			4.29 kJ/kg 333C to 2.5 V	21370 W/kg 333C (2kA)

Electrostatic, electrolytic and electrochemical capacitors

Capacitors store electric charge onto two electrodes separated by an electric field semi-insulating (dielectric) medium. Electrostatic capacitors feature planar electrodes onto which electric charge accumulates. Electrolytic capacitors use a liquid electrolyte as one of the electrodes and the electric double layer effect upon the surface of the dielectric-electrolyte boundary to increase the amount of charge stored per unit volume. Electric double-layer capacitors extend both electrodes with a nanopourous material such as activated carbon to significantly increase the surface area upon which electric charge can accumulate, reducing the dielectric medium to nanopores and a very thin high permittivity separator.

While capacitors tend not to be as temperature sensitive as batteries, they are significantly capacity constrained and without the strength of chemical bonds suffer from self-discharge. Power-to-weight ratio of capacitors is usually higher than batteries because charge transport units within the cell are smaller (electrons rather than ions), however energy-to-weight ratio is conversely usually lower.

Capacitor type	Capacity	Volts	Temp.	Energy-to-weight ratio	Power-to-weight ratio
ACT Premlis Lithium ion capacitor	2000 F	4.0 V	25 °C	54 kJ/kg to 2.0 V	44.4 W/kg @ 5 A
				31 kJ/kg to 2.0 V	850 W/kg @ 10 A
Nesccap Electric double-layer capacitor	5000 F	2.7 V	25 °C	19.58 kJ/kg to 1.35 V	5.44 W/kg C/1 (1.875 A)
				5.2 kJ/kg to 1.35 V	5,200 W/kg @ 2,547A
EEStor EESU barium titanate supercapacitor	30.693 F	3500 V	85 °C	1471.98 kJ/kg	80.35 W/kg C/5
				1471.98 kJ/kg	8,035 W∕kg 20 C
General Atomics 3330CMX2205 High Voltage Capacitor	20.5 mF	3300 V	? °C	2.3 kJ/kg	6.8 MW/kg @ 100 kA

Fuel cell stacks and flow cell batteries

Fuel cells and flow cells, although perhaps using similar chemistry to batteries, have the distinction of not containing the energy storage medium or fuel. With a continuous flow of fuel and oxidant, available fuel cells and flow cells continue to convert the energy storage medium into electric energy and waste products. Fuel cells distinctly contain a fixed electrolyte whereas flow cells also require a continuous flow of electrolyte. Flow cells typically have the fuel dissolved in the electrolyte.

Fuel cell type	Dry weight	Power-to-weight ratio	Example Use
Redflow Power+BOS ZB600 10kWh ZBB	900 kg	5.6 W/kg (9.3 W/kg peak)	Rural Grid support
Ceramic Fuel Cells BlueGen MG 2.0 CHP SOFC	200 kg	10 W/kg
		15 W/kg CHP
MTU Friedrichshafen 240 kW MCFC HotModule 2006	20 t	12 W/kg
Smart Fuel Cell Jenny 600S 25W DMFC	1.7 kg	14.7 W/kg	Portable military electronics
UTC Power PureCell 400 kW PAFC	27,216 kg	14.7 W/kg
GEFC 50V50A-VRB Vanadium redox battery	80 kg	31.3 W/kg (125 W/kg peak)
Ballard Power Systems Xcellsis HY-205 205 kW PEMFC	2,170 kg	94.5 W/kg	Mercedes-Benz Citaro O530BZTemplate:Cref2
UTC Power/NASA 12 kW AFC	122 kg	98 W/kg	Space Shuttle orbiterTemplate:Cref2
Ballard Power Systems FCgen-1030 1.2 kW CHP PEMFC	12 kg	100 W/kg	Residential cogeneration
Ballard Power Systems FCvelocity-HD6 150 kW PEMFC	400 kg	375 W/kg	Bus and heavy duty
Honda 2003 43 kW FC Stack PEMFCTemplate:Cref2	43 kg	1000 W/kg	Honda FCX ClarityTemplate:Cref2
Lynntech, Inc. PEMFC lab prototype	347 g	1,500 W/kg

Photovoltaics

Photovoltaic Panel type	Power-to-weight ratio
Thyssen Solartec 128W Nanocrystalline Si Triplejunction PV module	6 W/kg
Suntech/UNSW HiPerforma PLUTO220-Udm 220W Ga-F22 Polycrystalline Si PV module	13.1 W/kg STP
	9.64 W/kg nominal
Global Solar PN16015A 62W CIGS polycrystalline thin film PV module	40 W/kg
Able (AEC) PUMA 6 kW GaInP2/GaAs/Ge-on-Ge Triplejunction PV array	65 W/kg
Current spacecraft grade	~77 W/kg
ITO/InP on Kapton foil	2000 W/kg

Vehicles

Power-to-weight ratios for vehicles are usually calculated using Curb weight (for cars) or wet weight (for motorcycles) – in other words, excluding weight of the driver and any cargo. This could be slightly misleading, especially with regard to motorcycles, where the driver might weigh 1/3 to 1/2 as much as the vehicle itself. In the sport of competitive cycling athlete's performance is increasingly being expressed in VAMs and thus as a power-to-weight ratio in W/kg. This can be measured through the use of a bicycle powermeter or calculated from measuring incline of a road climb and the rider's time to ascend it.

Utility and practical vehicles

Most vehicles are designed to meet passenger comfort and cargo carrying requirements. Different designs trade off power-to-weight ratio to increase comfort, cargo space, fuel economy, emissions control, energy security and endurance. Reduced drag and lower rolling resistance in a vehicle design can facilitate increased cargo space without increase in the (zero cargo) power-to-weight ratio. This increases the role flexibility of the vehicle. Energy security considerations can trade off power (typically decreased) and weight (typically increased), and therefore power-to-weight ratio, for fuel flexibility or drive-train hybridisation. Some utility and practical vehicle variants such as hot hatches and sports-utility vehicles reconfigure power (typically increased) and weight to provide the perception of sports car like performance or for other psychological benefit. Rail locomotives require high mass to maintain adhesive traction on the rails, therefore improving the power-to-weight ratio by reducing mass is not necessarily beneficial. However choice of rail locomotive traction system (i.e. AC VFD over DC) can support improved power-to-weight ratio by reducing mass for the same adhesion.

Notable low ratio, (listed as weight to power)

Vehicle	Power	Weight	Weight to Power ratio
Benz Patent Motorwagen 954 cc 1886	560 W / 0.75 bhp	265 kg / 584 lb	2.1 W/kg / 779 lb/hp
Stephenson's Rocket 0-2-2 steam locomotive with tender 1829	15 kW / 20 bhp	4,320 kg / 9524 lb	3.5 W/kg / 476 lb/hp
CBQ Zephyr streamliner diesel locomotive with railcars 1934	492 kW / 660 bhp	94 t / 208,000 lb	5.21 W/kg / 315 lb/hp
Alberto Contador's Verbier climb 2009 Tour de France on Specialized bike	420 W / 0.56 bhp	62 kg / 137 lb	6.7 W/kg / 245 lb/hp
Force Motors Minidor Diesel 499 cc auto rickshaw	6.6 kW / 8.8 bhp	700 kg / 1543 lb	9 W/kg / 175 lb/hp
PRR Q2 4-4-6-4 steam locomotive with tender 1944	5,956 kW / 7,987 bhp	475.9 t / 1,049,100 lb	12.5 W/kg / 131 lb/hp
Mercedes-Benz Citaro O530BZ H2 fuel cell bus 2002	205 kW / 275 bhp	14,500 kg / 32,000 lb	14.1 W/kg / 116 lb/hp
TGV BR Class 373 high-speed Eurostar Trainset 1993	12,240 kW / 16,414 bhp	816 t / 1,798,972 lb	15 W/kg / 110 lb/hp
General Dynamics M1 Abrams Main battle tank 1980	1,119 kW / 1500 bhp	55.7 t / 122,800 lb	20.1 W/kg / 81.9 lb/hp
BR Class 43 high-speed diesel electric locomotive 1975	1,678 kW / 2,250 bhp	70.25 t / 154,875 lb	23.9 W/kg / 69 lb/hp
GE AC6000CW diesel electric locomotive 1996	4,660 kW / 6,250 bhp	192 t / 423,000 lb	24.3 W/kg / 68 lb/hp
BR Class 55 Napier Deltic diesel electric locomotive 1961	2,460 kW / 3,300 bhp	101 t / 222,667 lb	24.4 W/kg / 68 lb/hp
International CXT 2004	164 kW / 220 bhp	6,577 kg / 14500 lb	25 W/kg / 66 lb/hp
Ford Model T 2.9 L flex-fuel 1908	15 kW / 20 bhp	540 kg / 1,200 lb	28 W/kg / 60 lb/hp
TH!NK City 2008	30 kW / 40 bhp	1038 kg / 2,288 lb	28.9 W/kg / 56.9 lb/hp
Messerschmitt KR200 Kabinenroller 191 cc 1955	6 kW / 8.2 bhp	230 kg / 506 lb	30 W/kg / 50 lb/hp
Wright Flyer 1903	9 kW / 12 bhp	274 kg / 605 lb	33 W/kg / 50 lb/hp
Tata Nano 624 cc 2008	26 kW / 35 bhp	635 kg / 1,400 lb	41.0 W/kg / 40 lb/hp
Bombardier JetTrain high-speed gas turbine-electric locomotive 2000	3,750 kW / 5,029 bhp	90,750 kg / 200,000 lb	41.2 W/kg / 39.8 lb/hp
Suzuki MightyBoy 543 cc 1988	23 kW / 31 bhp	550 kg / 1,213 lb	42 W/kg / 39 lb/hp
Mitsubishi i MiEV 2009	47 kW / 63 bhp	1,080 kg / 2,381 lb	43.5 W/kg / 37.8 lb/hp
Holden FJ 2,160 cc 1953	44.7 kW / 60 bhp	1,021 kg / 2,250 lb	43.8 W/kg / 37.5 lb/hp
Chevrolet Kodiak/GMC Topkick LYE 6.6 L 2005	246 kW / 330 bhp	5126 kg / 11,300 lb	48 W/kg / 34.2 lb/hp
DOE/NASA/0032-28 Chevrolet Celebrity 502 cc ASE Mod II 1985	62.3 kW / 83.5 bhp	1,297 kg / 2,860 lb	48.0 W/kg / 34.3 lb/hp
Suzuki Alto 796 cc 2000	35 kW / 46 bhp	720 kg / 1,587 lb	49 W/kg / 35 lb/hp
Land Rover Defender 2.4 L 1990	90 kW / 121 bhp	1,837 kg / 4,050 lb	49 W/kg / 33 lb/hp

Common power, (Listed as weight to power)

Vehicle	Power	Weight	Weight-to-Power ratio
Toyota Prius 1.8 L 2010 (petrol only)	73 kW / 98 bhp	1,380 kg / 3,042 lb	53 W/kg / 31 lb/hp
Bajaj Platina Naked 100 cc 2006	6 kW / 8 bhp	113 kg / 249 lb	53 W/kg / 31 lb/hp
Subaru R2 type S 2003	47 kW / 63 bhp	830 kg / 1,830 lb	57 W/kg / 29 lb/hp
Ford Fiesta ECOnetic 1.6 L TDCi 5dr 2009	66 kW / 89 bhp	1,155 kg / 2,546 lb	57 W/kg / 29 lb/hp
Volvo C30 1.6D DRIVe S/S 3dr Hatch 2010	80 kW / 108 bhp	1,347 kg / 2,970 lb	59.4 W/kg / 27.5 lb/hp
Ford Focus ECOnetic 1.6 L TDCi 5dr Hatch 2009	81 kW / 108 bhp	1,357 kg / 2,992 lb	59.7 W/kg / 27 lb/hp
Ford Focus 1.8 L Zetec S TDCi 5dr Hatch 2009	84 kW / 113 bhp	1,370 kg / 3,020 lb	61 W/kg / 27 lb/hp
Honda FCX Clarity 4 kg Hydrogen 2008	100 kW / 134 bhp	1,600 kg / 3,528 lb	63 W/kg / 26 lb/hp
Hummer H1 6.6 L V8 2006	224 kW / 300 bhp	3,559 kg / 7,847 lb	63 W/kg / 26 lb/hp
Audi A2 1.4 L TDI 90 type S 2003	66 kW / 89 bhp	1,030 kg / 2,270 lb	64 W/kg / 25 lb/hp
Opel/Vauxhall/Holden/Chevrolet Astra 1.7 L CTDi 125 2010	92 kW / 123 bhp	1,393 kg / 3,071 lb	66 W∕kg / 24.9 lb∕hp
Mini (new) Cooper 1.6D 2007	81 kW / 108 bhp	1,185 kg / 2,612 lb	68 W/kg / 24 lb/hp
Toyota Prius 1.8 L 2010 (electric boost)	100 kW / 134 bhp	1,380 kg / 3,042 lb	72 W/kg / 23 lb/hp
Ford Focus 2.0 L Zetec S TDCi 5dr Hatch 2009	100 kW / 134 bhp	1,370 kg / 3,020 lb	73 W/kg / 23 lb/hp
General Motors EV1 electric car Gen II 1998	102.2 kW / 137 bhp	1,400 kg / 3,086 lb	73 W/kg / 23 lb/hp
Toyota Venza I4 2.7 L FWD 2009	136 kW / 182 bhp	1,706 kg / 3,760 lb	80 W/kg / 20.7 lb/hp
Ford Focus 2.0 L Zetec S 5dr Hatch 2009	107 kW / 143 bhp	1,327 kg / 2,926 lb	81 W/kg / 20 lb/hp
Fiat Grande Punto 1.6 L Multijet 120 2005	88 kW / 118 bhp	1,075 kg / 2,370 lb	82 W/kg / 20 lb/hp
Mini (classic) 1275GT 1969	57 kW / 76 bhp	686 kg / 1,512 lb	83 W/kg / 20 lb/hp
Opel/Vauxhall/Holden/Chevrolet Astra 2.0 L CTDi 160 2010	118 kW / 158 bhp	1,393 kg / 3,071 lb	85 W∕kg / 19.4 lb∕hp
Ford Focus 2.0 auto 2007	104.4 kW / 140 bhp	1,198 kg / 2,641 lb	87.1 W/kg / 19 lb/hp
Subaru Legacy/Liberty 2.0R 2005	121 kW / 162 bhp	1,370 kg / 3,020 lb	88 W/kg / 19 lb/hp
Subaru Outback 2.5i 2008	130.5 kW / 175 bhp	1,430 kg / 3,153 lb	91 W/kg / 18 lb/hp
Smart Fortwo 1.0 L Brabus 2009	72 kW / 97 bhp	780 kg / 1,720 lb	92 W/kg / 18 lb/hp
Toyota Venza V6 3.5 L AWD 2009	200 kW / 268 bhp	1,835 kg / 4,045 lb	109 W/kg / 15 lb/hp
Toyota Venza I4 2.7 L FWD 2009 with Lotus mass reduction	136 kW / 182 bhp	1,210 kg / 2,667 lb	112.2 W/kg / 14.7 lb/hp
Toyota Hilux V6 DOHC 4 L 4×2 Single Cab Pickup ute 2009	175 kW / 235 bhp	1,555 kg / 3,428 lb	112.5 W/kg / 14.6 lb/hp
Toyota Venza V6 3.5 L FWD 2009	200 kW / 268 bhp	1,755 kg / 3,870 lb	114 W/kg / 14.4 lb/hp

Performance luxury, roadsters and mild sports, (Listed as weight to power)

Increased engine performance is a consideration, but also other features associated with luxury vehicles. Longitudinal engines are common. Bodies vary from hot hatches, sedans (saloons), coupés, convertibles and roadsters. Mid-range dual-sport and cruiser motorcycles tend to have similar power-to-weight ratios.

Vehicle	Power	Weight	Weight-to-power ratio
Honda Accord sedan V6 2011	202 kW / 271 bhp	1630 kg / 3593 lb	124 W/kg / 13.26 lb/hp
Mini (new) Cooper 1.6T S JCW 2008	155 kW / 208 bhp	1205 kg / 2657 lb	129 W/kg / 13 lb/hp
Mazda RX-8 1.3 L Wankel 2003	173 kW / 232 bhp	1309 kg / 2888 lb	141 W/kg / 12 lb/hp
Holden Statesman/Caprice / Buick Park Avenue / Daewoo Veritas 6 L V8 2007	270 kW / 362 bhp	1891 kg / 4170 lb	143 W/kg / 12 lb/hp
Kawasaki KLR650 Gasoline DualSport 650 cc	26 kW / 35 bhp	182 kg / 401 lb	143 W/kg / 11 lb/hp
NATO HTC M1030M1 Diesel/Jet fuel DualSport 670 cc	26 kW / 35 bhp	182 kg / 401 lb	143 W/kg / 11 lb/hp
Harley-Davidson FLSTF Softail Fat Boy Cruiser 1,584 cc 2009	47 kW / 63 bhp	324 kg / 714 lb	145 W/kg / 11.3 lb/hp
BMW 7 Series 760Li 6 L V12 2006	327 kW / 439 bhp	2250 kg / 4960 lb	145 W/kg / 11 lb/hp
Subaru Impreza WRX STi 2.0 L 2008	227 kW / 304 bhp	1530 kg / 3373 lb	148 W/kg / 11 lb/hp
Honda S2000 roadster 1999Potter or Ceramic Artist Truman Bedell from Rexton, has interests which include ceramics, best property developers in singapore developers in singapore and scrabble. Was especially enthused after visiting Alejandro de Humboldt National Park.	183.88 kW / 240 bhp	1250 kg / 2723 lb	150 W/kg / 11 lb/hp
GMH HSV Clubsport / GMV VXR8 / GMC CSV CR8 / Pontiac G8 6 L V8 2006	317 kW / 425 bhp	1831 kg / 4037 lb	173 W/kg / 9.5 lb/hp
Tesla Roadster 2011	215 kW / 288 bhp	1235 kg / 2723 lb	174 W/kg / 9.5 lb/hp

Sports vehicles and aircraft, (Listed as weight to power)

Power-to-weight ratio is an important vehicle characteristic that affects the acceleration and handling - and therefore the driving enjoyment - of any sports vehicle. Aircraft also depend on high power-to-weight ratio to achieve sufficient lift.

Vehicle	Power	Weight	Weight-to-power ratio
Lotus Elise SC 2008	163 kW / 218 bhp	910 kg / 2006 lb	179 W/kg / 9 lb/hp
Ferrari Testarossa 1984	291 kW / 390 bhp	1506 kg / 3320 lb	193 W/kg / 9 lb/hp
Artega GT	220 kW / 300 bhp	1100 kg / 2425 lb	200 W/kg / 8 lb/hp
Lotus Exige GT3 2006	202.1 kW / 271 bhp	980 kg / 2160 lb	206 W/kg / 8 lb/hp
Chevrolet Corvette C6	321 kW / 430 bhp	1441 kg / 3177 lb	223 W/kg / 7 lb/hp
Suzuki V-Strom 650 V-twin DualSport 650 cc	50 kW / 67 bhp	194 kg / 427 lb	258 W/kg / 6.4 lb/hp
Chevrolet Corvette C6 Z06	376 kW / 505 bhp	1421 kg / 3133 lb	265 W/kg / 6.2 lb/hp
Porsche 911 GT2 2007	390 kW / 523 bhp	1440 kg / 3200 lb	271 W/kg / 6.1 lb/hp
Lamborghini Murciélago LP 670-4 SV 2009	493 kW / 661 bhp	1550 kg / 3417 lb	318 W/kg / 5.1 lb/hp
McLaren F1 GT 1997	467.6 kW / 627 bhp	1220 kg / 2690 lb	403 W/kg / 4.3 lb/hp
Bombardier Dash 8 Q400 turboprop airliner	7,562 kW / 10,142 bhp	17,185 kg / 37,888 lb	440 W/kg / 3.7 lb/hp
Supermarine Spitfire Fighter aircraft 1936	1,096 kW / 1,470 bhp	2,309 kg / 5,090 lb	475 W/kg / 3.46 lb/hp
Messerschmitt Bf 109 Fighter aircraft 1935	1,085 kW / 1,455 bhp	2,247 kg / 4,954 lb	483 W/kg / 3.40 lb/hp
Thunderbolt Land speed record car	3504 kW / 4700 bhp	7 t / 15432 lb	500 W/kg / 3.28 lb/hp
Ferrari FXX 2005	597 kW / 801 bhp	1155 kg / 2546 lb	517 W/kg / 3.2 lb/hp
Polaris Industries Assault Snowmobile 2009	115 kW / 154 bhp	221 kg / 487 lb	523 W/kg / 3.16 lb/hp
Ultima GTR 720 2006	536.9 kW / 720 bhp	920 kg / 2183 lb	583 W/kg / 3 lb/hp
Honda CBR1000RR 2009	133 kW / 178 bhp	199 kg / 439 lb	668 W/kg / 2.5 lb/hp
Ariel Atom 500 V8 2011	372 kW / 500 bhp	550 kg / 1212 lb	676.3 W/kg / 2.45 lb/hp
Peugeot 208 T16 Pikes Peak 2013	652 kW / 875 bhp	875 kg / 1930 lb	745 W/kg / 2.2 lb/hp
KillaCycle Drag racing electric motorcycle	260 kW / 350 bhp	281 kg / 619 lb	925 W/kg / 1.77 lb/hp
MTT Turbine Superbike 2008	213.3 kW / 286 bhp	227 kg / 500 lb	940 W/kg / 1.75 lb/hp
Vyrus 987 C3 4V V supercharged motorcycle 2010	157.3 kW / 211 bhp	158 kg / 348.3 lb	996 W/kg / 1.65 lb/hp
BMW Williams FW27 Formula One 2005	690 kW / 925 bhp	600 kg / 1323 lb	1150 W/kg / 1.43 lb/hp
Honda RC211V MotoGP 2004-6	176.73 kW / 237 bhp	148 kg / 326 lb	1194 W/kg / 1.37 lb/hp
Boeing 747-300 at Mach 0.84 cruise, 35,000 ft altitudeTemplate:Disputed-inline	245 MW / 328,656 bhp	178.1 t / 392,800 lb	1376 W/kg / 1.20 lb/hp
John Force Racing Funny Car NHRA Drag Racing 2008	5,963.60 kW / 8,000 bhp	1043 kg / 2,300 lb	5717 W/kg / 0.30 lb/hp

See also

• Thrust-to-weight ratio
• Vehicle metrics
• Energy density
• Propulsive efficiency

References

43 year old Petroleum Engineer Harry from Deep River, usually spends time with hobbies and interests like renting movies, property developers in singapore new condominium and vehicle racing. Constantly enjoys going to destinations like Camino Real de Tierra Adentro.

External links

• Measurespeed.com - Power to Weight Ratio Calculator