The energy efficiency in transport is the useful travelled distance, of passengers, goods or any type of load; divided by the total energy put into the transport propulsion means. The energy input might be rendered in several different types depending on the type of propulsion, and normally such energy is presented in liquid fuels, electrical energy or food energy. The inverse of the energy efficiency in transport is the energy consumption in transport.
Energy consumption in transport is often described in terms of fuel consumption, fuel consumption being the reciprocal of fuel economy. and linked with a means of propulsion which uses chemical energy, whilst energy efficiency in general is applicable to any sort of propulsion. In order to compare the energy efficiency in any type of vehicle, it helps to use the International System of Units including joules for energy and metres for distance. The more efficient the vehicle, the more metres it covers with one joule (more efficiency), or the fewer joules it uses to travel over one metre (less consumption). The efficient use of energy in transport largely varies by means of transport. Different types of transport consume from some dozen kilojoules per kilometre (kJ/km) for a bicycle to several thousand for a car. Several distinctions are often not clear: The energy content of liquid fuels is well known, but not always exactly which fuel is used or whether its value was converted or not. The energy content of food varies greatly so that for walking and vehicles using human power its value of metabolic energy is used. If the food for the basal metabolic rate, i.e. the energy needed for living, is included, as it most often is, the efficiency is much lower than if it is excluded, as for the drivers of motor vehicles. The energy content of electricity itself is an exact definition, but it undergoes many conversions e.g. from a power station to the vehicle, so that comparisons require defining where the electricity is measured and/or how it is produced.
Via type of fuel used and rate of fuel consumption, energy efficiency is also often related to operating cost ($/km) and environmental emissions (e.g. COe/km). The same considerations are beginning to be used also for type of food.
Units of measurement In the International System of Units, the energy efficiency in transport is measured in terms of metre per joule, or m/J. Nonetheless, several conversions are applicable, depending on the unit of distance and on the unit of energy. For liquid fuels, normally the quantity of energy input is measured in terms of the liquid's volume, such as litres or gallons. For propulsion which runs on electricity, normally kWh is used, while for any type of human-propelled vehicle, the energy input is measured in terms of Calories. It is typical to convert between different types of energy and units.
For passenger transport, the energy efficiency is normally measured in terms of passengers times distance per unit of energy, in the SI, passengers metres per joule (pax.m/J); while for cargo transport the energy efficiency is normally measured in terms of the mass of transported cargo times distance per unit of energy, in the SI, kilograms metres per joule (kg.m/J). Volumetric efficiency with respect to vehicle capacity may also be reported, such as passenger-mile per gallon (PMPG), obtained by multiplying the miles per gallon of fuel by either the passenger capacity or the average occupancy. The occupancy of personal vehicles is typically lower than capacity by a considerable degree and thus the values computed based on capacity and on occupancy will often be quite different.
Typical conversions into SI unit Jouleslitre of diesel 0.358 × 108litre of petrol0.3 × 108US gallon of petrol (gasoline)1.3 × 108Imp. gallon of petrol (gasoline)1.6 × 108kilocalorie4.2 × 103kWh3.6 × 106BTU1.1 × 103
Liquid fuels Energy efficiency is expressed in terms of fuel economy: distance per vehicle per unit fuel volume; e.g., km/L or miles per gallon (US or imperial). distance per vehicle per unit fuel mass; e.g., km/kg.Aeroplane Efficiency, Fédération Aéronautique Internationale, "FAI – The World Air Sports Federation" distance per vehicle per unit energy; e.g., miles per gallon equivalent (mpg-e).
Energy consumption (reciprocal efficiency) is expressed terms of fuel consumption: volume of fuel (or total energy) consumed per unit distance per vehicle; e.g. l/100 km or MJ/100 km. volume of fuel (or total energy) consumed per unit distance per passenger; e.g., l/(100 passenger·km). volume of fuel (or total energy) consumed per unit distance per unit mass of cargo transported; e.g., l/100 kg·km or MJ/t·km.
Electricity Electricity consumption: electrical energy used per vehicle per unit distance; e.g., kWh/100 km. Producing electricity from fuel requires much more primary energy than the amount of electricity produced.
Food energy Energy consumption: Calories processed by the body's metabolism per kilometre; e.g., Cal/km or kcal/km. Calories processed by the body's metabolism per mile; e.g., Cal/miles.
Land Passenger Transport
Table Overview In the following table the energy efficiency and energy consumption for different types of passenger land vehicles and modes of transport, as well as standard occupancy rates, are presented, with the sources for these figures in references.
For the conversion amongst units of energy, 1 litre of petrol amounts to 34.2 MJ, 1 kWh to 3.6 MJ and 1 kilocalorie to 4184 J. For the car occupation ratio, the value of 1.2 passengers per automobile is considered. In Europe this value slightly increases to 1.4.
+Energy Efficiency and Consumption of Land Passenger Transport meansMode of transportEnergy EfficiencyEnergy consumptionAverage number of passengers per vehicleEnergy EfficiencyEnergy consumptionmpg(US) of petrolmpg(imp) of petrolkm/L of petrolkm/MJm/JL(petrol)/ 100 kmkWh/100 kmkcal/kmMJ/100 kmJ/m(m·pax)/JJ/(m·pax)Human propelledWalking68 kg person at 4 km/h, including basal metabolic rate4.550.004556.152.522.02201.00.00455220Walking68 kg person at 4.5 km/h, excluding basal metabolic rate, data from Von Kármán–Gabrielli diagram24.20.02421.1489.884.1341.31.00.024241.3Velomobile with enclosed recumbent12.350.012352.25 (0.50)19.358.1811.00.0123581Bicycle Measured mean of 18 healthy, untrained men and women at mean 20 km/h including basal metabolic rate.8.850.008853.142711.31131.00.00885113Bicycle Calculated values using a sports bicycle at 20 km/h, assuming a muscular energy efficiency of 24%, excluding basal metabolic rate.200.0201.4125.0501.00.02050Motor assistElectric bicycle23.210.023211.2 Measured mean value at battery output with no pedalling at 25 km/h.10.334.3431.00.0232143Electric kick scooter24.870.024871.129.614.00401.00.0248740AutomobileSolar Car14.930.014931.8616.016.70671.00.0149367GEM NER2.650.0026510.5090.3437.803781.20.00317315General Motors EV11.210.0012123.00197.9082.808281.20.00145690Chevrolet Volt99.31119.2742.221.230.001232.3722.50193.5981.008101.20.00148675Daihatsu Charade83.80100.6335.631.040.001042.8126.67229.4596.009601.20.00125800Volkswagen Polo61.8874.3126.310.770.000773.8038326.97136.813681.20.000871140SEAT Ibiza 1.4 TDI Ecomotion61.8874.3126.310.770.000773.8038326.97136.813681.20.000871140Renault Clio33.6040.3213.910.420.00042766.5572.18239.423941.20.000491995Volkswagen Passat26.7632.1111.370.330.000338.7983.51718.53300.6330061.20.000392505Cadillac CTS-V13.8216.605.880.170.0001717.02161.671391.01582.0058201.20.000214850Bugatti Veyron9.7911.754.160.120.0001224.04228.331964.63822.0082201.20.000156850Nissan Leaf1.490.0014918.64160.3767.106711.20.00179559Toyota Prius56.0667.3223.830.700.000704.2039.86342.97143.5014351.20.000841196Tesla Model S1.610.0016117.25148.4262.106211.20.00193517Tesla Model 31.760.0017615129.06545401.20.00222450Aptera 2 Series423507.99179.825.280.005280.53543181801.20.00666150Aptera solar EV4.50.00456.252.56222201.20.00545183BusesMCI 102DL36.037.242.560.070.0000739.04370.833190.731335.001335011.00.000821214Proterra Catalyst 40' E20.23The range used is the midpoint of the effective operating range.0.00023121.541044.20437.60437611.00.00319313TrainsUrban rail0.00231432CR400AF (cn)~65%0.00475210 at 350 km/hJR East (jp)~0.0109192CP-Lisbon (pt)27.7%Relatório & Contas da CP; página 16; 20120.01304Basel (ch)~50.0%0.00215465
Land transport means Walking
A person walking at requires approximately of food energy per hour, which is equivalent to 4.55 km/MJ. of petrol contains about of energy, so this is approximately equivalent to .
Velomobile
Velomobiles are mostly tricycles, sometimes bicycles or quadracycles, with fully enclosed fairings. Because of the extra weight, the efficiency is slightly reduced uphill and at low speeds, where rolling resistance dominates. At higher speeds they become more efficient than any other vehicles because of their small frontal area and aerodynamic shape.
At a speeds of over , a velomobile at the same speed needs less than half the power of an unfaired racing bicycle.
Input energy from food used by humans is over 4 times higher. (using 24% muscular efficiency) If this is considered, velomobiles with electric motors are the most efficient vehicles in spite of the extra weight of their batteries, as long as they do not become too heavy and continue to use low-resistance tires.
With human power, there is a tradeoff between low aerodynamic drag and cooling of the body, influencing both power capability and comfort, and therefore also of speed and efficiency.
Bicycle
A standard lightweight, moderate-speed bicycle is one of the most energy-efficient forms of transport if food production is not counted or is optimal. Compared with walking, a cyclist riding at requires about half the food energy per unit distance: 27 kcal/km, per 100 km, or 43 kcal/mi. This converts to about . This means that a bicycle will use between 10 and 25 times less energy per distance travelled than a personal car, depending on fuel source and size of the car. This figure does depend on the speed and mass of the rider: greater speeds give higher air drag and heavier riders consume more energy per unit distance. In addition, because bicycles are very lightweight (usually between 7–15 kg) this means they consume very low amounts of materials and energy to manufacture. In comparison to an automobile weighing 1500 kg or more, a bicycle typically requires 100–200 times less energy to produce than an automobile.
Motorised cycles
There is no clear distinction of construction between motorised bicycles or tricycles and low-powered motorcycles or motorscooters but the fuel consumption is influenced by mandated speed ranges and number of riders.
Petrol (gasoline) Engines using petrol are heat engines limited in efficiency, so that only a fraction of the energy is available for propulsion.