Advantages of electric vehicles
Electric vehicle (EV) became popular in California. Recently I can find more than one Tesla car during my daily commute. There are a couple of advantages of EV compared with gas powered vehicles; (1) higher cost efficiency (higher MPGe1), (2) lower maintainance cost, and (3) tax incentives and rebate (read an article in energysage.com, one in a utility company, and a site from U.S. Department of Energy).
Long-range EV and increasing number of charging points are good for daily driving?
EV.data %>% filter(type=="EV") %>% ggplot(aes(x=`battery capacity (kW)`,y=range,color=make)) + geom_point() + scale_y_continuous(limits=c(0,350)) + scale_x_continuous(limits=c(0,100)) + theme(legend.position="bottom") + labs(x="Battery capacity (kW)", y="Driving range (mile)", title="Fig. 1")
Average of daily commute distance in US is 13.6 miles in 2009 National Household travel Survey (NHTS) and 95% of commute is less than 40 miles. Due to increasing Lithium battery capacity, recent EV models (such as Tesla, Nissan Leaf plus, Chevy Bolt, Hyndai Kona, etc) can drive more than 200 miles with one fully charged battery (see Fig. 1 redrawn from a comparison Table in insideEVs.com), which is sufficient for most of car commuters. However, we need to drive beween our kid school and a pool (for synchronized swimming practice) in addition to commute to work place, resulting 130 miles per day. Furthermore, there are increased density of public available charging stations found in ChargePoint netwowrk, for example. So it seems a recent progress of EV world is perfect for us.
Needs more cargo space!
I noticed that an important aspect of car specification is missing in almost all articles on EV; cargo space. I assume that for most of daily commuters do not need large cargo space. However our car needs relatively large cargo space to carry bags for works and school as well as many stuffs for synchronized swimming practices, such as a yoga mat, two square water carrier jug/container, snacs, water bottle, and another bag for swimming. Our current compact car has 17 cubit feet, which is not sufficient. Adding cargo volume data to the table, I found that there are only few EVs has cargo space larger than 20 cubic feet. Furthermore, there seems no correlation between price and cargo volume (Fig. 2), meaning that cargo volume is not important factor to determine price (MSRP)2. Moreover, there are no high correlation between any of other parameters. Please make SUVs with larger cargo space at low price!
GGally package is used to draw Fig. 2.
EV.data %>% filter(type=="EV") %>% ggpairs(columns=c("range","mpge","cargo_volume_cu_ft","battery capacity (kW)","MSRP"), columnLabels =c("range (miles)","mpge","cargo vol (cu ft)","bettery capacity (kW)","price ($)"),lower=list(mappings=aes(color=make,label=model),legend=c(5,2))) + theme(strip.text.y=element_text(angle=0)) + labs(title="Fig. 2") 
MPGe: (Miles per gallon equivallent) “For most vehicles, the label shows City, Highway, and Combined MPG (miles per gallon) values. The Combined MPG value is the most prominent for the purpose of quick and easy comparison across vehicles. Some form of the miles per gallon metric has been on vehicle labels since 1977. Combined fuel economy is a weighted average of City and Highway MPG values that is calculated by weighting the City value by 55% and the Highway value by 45%. For those vehicles that do not use liquid fuels—such as electric vehicles, plug-in hybrid electric vehicles operating on electricity, and compressed natural gas vehicles—the labels display miles per gallon of gasoline-equivalent (MPGe). Think of this as being similar to MPG, but instead of presenting miles per gallon of the vehicle’s fuel type, it represents the number of miles the vehicle can go using a quantity of fuel with the same energy content as a gallon of gasoline. This allows a reasonable comparison between vehicles using different fuels. For example, you can use MPGe to compare a compressed natural gas (CNG) vehicle with a gasoline vehicle; even though CNG is not dispensed or burned in gallons.” (cited from fueleconomy.gov web site).↩
MSRP: “manufacturer’s suggested retail price, is quite simply the price that the manufacturer suggests that the dealer should ask for a car. This is also referred to as the retail price, or the dollar amount that a retailer should be asking for the car according to the automaker. Think of it as the car-dealer version of the price tag you see on a television at an electronics store.” (cited from www.autotrader.com).↩