Assessing the transport parity of battery electric vehicles 2017

Plug-in electric vehicles have dramatically increased in presence at the private vehicle market in recent years, even though EV (electric vehicle) sales still constitute less than 1.0% of total US vehicle sales volume, split between hybrid PHEVs (plug-in hybrid electric vehicles) and fully-electric BEVs (battery electric vehicles). This report is aiming to analyze several performance parameters of BEVs in comparison to internal combustion cars in order to evaluate their future competitiveness and the rate of penetration into the private vehicle market.  In summary, as of 2016, mainstream BEVs were rapidly advancing on ICE cars in terms of travel range due to larger and better battery packs, while also offering superiority in terms of energy efficiency.

The extended commercial report can be purchased at LNRG Technology digital store (below).

Plug-in electric vehicles have dramatically increased in presence at the private vehicle market in recent years, even though EV sales still constitute less than 1.0% of total US vehicle sales volume, split between hybrid PHEVs and fully-electric BEVs. Due to greater BEVs growth rate compared with PHEVs, some already predict BEV domination of the private transportation market within several years. Nevertheless, the transition to electric transportation may still encounter various obstacles, including technology, infrastructures, battery supply and of course regulation. Furthermore, it is also very much possible that the current mainstream scheme of private vehicle ownership could shift to smart mobility models, such as car-sharing, car-pooling, public transport on demand, autonomous drive, etc. This report is aiming to analyze several performance parameters of BEVs in comparison to internal combustion cars in order to evaluate their future competitiveness and the rate of penetration into the private vehicle market.

This analysis has been performed utilizing the 2016 annual US sales figures of plug-in electric vehicles published by Cleantechnica and technical details of relevant 2016 EV models as rated by manufacturers. The specs of top 7 fully-electric BEV models in terms of US sales were utilized for the estimate of weighted average of vehicle's battery energy capacity, vehicle's net weight and vehicle's travel range. PHEVs were disregarded in this study due to the complication of comparing vehicles with two propulsion systems. As for 2016, top BEV models in terms of US sales included Tesla S, Tesla X, Nissan Leaf, BMW i3, Volkswagen e-Golf, Chevy Spark EV and Kia Soul EV. A single internal combustion engine (ICE) vehicle was utilized for comparison - the gasoline-powered 2016 model Toyota Corolla. The weighted average and standard deviation of EV performance parameters is depicted at the following charts in comparison to parallel figures of an ICE vehicle, with energy content of gasoline rated in watt-hours for proper comparison.

Figure 1. Energy-per-weight (Wh/kg) is equivalent to battery energy capacity per BEV weight in comparison to fuel tank energy capacity per ICE vehicle weight. Energy-per-weight can serve as a tool to measure vehicle's normalized energy capacity.

Energy-per-weight is addressing vehicle's normalized energy capacity, putting differently sized vehicles on the same scale. We can see that from 2014 to 2016 there had been a notable improvement in weighted energy-per-weight of BEVs, whereas this characteristic for an ICE vehicle has been pretty stable. Notably, the highest 2016 figures of energy-per-weight for BEVs was obtained by Tesla X with 38 Wh/kg, whereas the lowest figure was obtained by Chevy Spark EV with 15 Wh/kg; in comparison ICE vehicles typically show a much higher ratio of almost 350 Wh/kg. It should be mentioned that some EV manufacturers specify the full capacity of their Li-ion battery, whereas others specify only the usable capacity; for the matter of this study the full capacity was utilized (if available).

Figure 2. Range-per-weight (km/kg) is equivalent to vehicle's maximum range per BEV weight in comparison to full-tank travel range per ICE vehicle weight. Range-per-weight can serve as a measure for normalized vehicle's travel range.

Range-per-weight is a normalized parameter to compare BEV and ICE vehicles in terms of range, while neutralizing the size factor. The most impressive BEV range-per-weight figure in 2016 was obtained by Tesla Model-S with 0.18 km/kg, whereas the least range-per-weight was obtained by Volkswagen e-Golf with 0.09 km/kg. BEV weighted range-per-weight ratio rose from 2015 to 2016, indicating stronger dominance of BEVs with higher-capacity batteries and thus longer vehicle range, such as Tesla Model-S. ICE vehicles typically show significantly higher values of range-per-weight, with values of about 0.50 km/kg, mostly due to a much higher energy content of gasoline fuel tank. The gap between BEV and ICE vehicles in terms of range-per-weight is still significant, but the gap seems to be rapidly narrowing.

Energy-per-range is addressing vehicle's normalized energy efficiency - how much kWh of energy does a vehicle require to travel one kilometer, which is somewhat equivalent to mpg (miles-per-gallon) rating. Notably, the best 2016 figures of energy-per-range for BEVs were obtained by Chevy Spark EV with 144 Wh/km, whereas the worst performance was obtained by Tesla X with 224 Wh/km; the weighted average of energy-per-range for 7 top-sold EVs in US was 187 Wh/km - somewhat worse than 169 Wh/km and 173 Wh/km in 2015 and 2014, which indicates a larger share of large EVs with appropriately large batteries. In comparison, ICE vehicles have a much worse performance of above 600 Wh/km, which has shown some improvement over the past decade.

While assessing the "transport parity" of battery electric vehicles (BEVs), hand we notice a much more efficient propulsion system of EVs in comparison to ICE cars on one hand, while on the other hand the energy content of ICE vehicles is still far more superior than the battery energy content of BEVs. Recently, we can witness a growing energy capacity of BEVs with increasingly better and apparently larger batteries, which had boosted the EPA range of EVs to 296km weighted average as of 2016 (compared with 212km in 2014 and 232km in 2015), thus rapidly closing the gap with ICE vehicles, which can typically travel 450-700km per full gasoline tank. The obvious increase in EV range is mostly a result of larger battery packs and thus also heavier vehicles, but also a notable increase in terms of range-per-weight. In summary, as of 2016, mainstream BEVs were rapidly advancing on ICE cars in terms of travel range due to larger and better battery packs, while also offering superiority in terms of energy efficiency.