*3.1. Scenario 1: Gasoline versus Electrical Vehicle Charged via Solar*

Scenario 1 evaluated the default values for a gasoline vehicle (termed the "baseline" simulation) against a BEV priced at the same value that receives a 30% tax credit and is completely charged by solar panels (termed the "comparison" simulation). An additional \$1000 is also charged for a home-charging station.

The break-even is on month 13, after the 30% tax credit is assigned (Figure 3), despite the assigned PVS acquisition costs in month 1. The simulation demonstrates the slower growth of total expenditures, but an initial increase in expenses associated with solar panel acquisition required to charge the BEV. Figure 4 provides cost breakouts for maintenance, energy, and insurance. While lifetime insurance costs are more expensive for the BEV, lifetime maintenance costs are less expensive and energy costs are nominal, as the BEV recharges through a PVS in this simulation.

The environmental analysis (also depicted in Figure 4) shows the value of the BEV most clearly. The BEV CO2 emission is largely in the production process and less than 1/6 of the ICEV emissions over its lifecycle. CO, PM, and NOx/NMOG emissions are negligible for the BEV option, whereas they continuously increase over the lifecycle of the ICEV. There is a clear advantage to the BEV in terms of the environment.

**Figure 3.** Break-even for Scenario 1 (curved line is a smoothed error curve estimate). Cost and environmental metrics for Scenario 1.

**Figure 4.** Cost and environmental metrics for Scenario 1.

## *3.2. Scenario 2: Gasoline vs. PHEV*

In Scenario 2, the baseline simulation is again the traditional, gasoline-based vehicle priced at \$30,000 with all default simulation values. The comparison option is an equally-priced PHEV (no tax credit) recharged through the electrical grid and obtaining 110 mpg (both electric and gas) with a battery offsetting 30% of vehicle power consumption. Again, a home charging station cost of \$1000 is included.

The break-even analysis (Figure 5) demonstrates that the PHEV and ICEV are approximately equal at month 16. Since the up-front cost differences was the home charging station, the analysis suggests about \$1000 savings every year for the adoption of a PHEV (not including residual analysis). The residual is smaller for the PHEV option. However, the TCO is lower (although not strikingly). Once again, insurance costs are clearly higher over the vehicle life cycle, maintenance and energy costs are lower (see Figure 6).

Figure 6 also depicts, the PHEV CO2 emissions are much lower than gasoline vehicles. Comparing Figure 6 to Figure 4 demonstrates that BHEV is superior in this category, as well as in all other emissions categories. PM is tied for PHEV and ICEV but zero post-production for BEVs.

**Figure 6.** Cost and environmental metrics from Scenario 2.

### **4. Discussion**

### *4.1. Findings and Relationships to Previous Studies*

This study provides a comparative simulation for various vehicle options, based on real-world data. The results of the two scenarios provided demonstrate that BEV and PHEV options may be both green for the pocketbook and the environment. BEVs have a much lower GHG emission profile, as found in previous studies [57]. BEVs rely on tax credits for an earlier break-even point as in Scenario 1, and these tax credits are likely to incentivize purchases [58] and allow for lower TCO [48]. Any initial up-front costs may be offset by savings depending on geographic considerations and other factors.

In Scenario 1, the results show an initial upfront cost increase for the BEV due to the purchase of requisite solar panels capable of powering the vehicle and the purchase of a home charging station. BEV lifecycle costs of maintenance are about half of that experienced by ICEV (\$3.5 K versus \$6.5 K), while energy costs are near zero after solar panel acquisition versus \$10 K for the ICEV. Insurance costs are higher for the BEV (\$14 K versus \$12.5 K ICEV), which is congruent with simulation input and previous research [48]. By eliminating grid use, the upfront cost reduces GHG emissions as in [12]. The production phase produces the majority of the lifecycle waste for BEVs.

In Scenario 2, the unincentivized purchase of a PHEV resulted in a 16-month break-even point congruent with previous research [28]. The higher initial cost due to the home installation of a charger was offset quickly due to lower maintenance costs similar to the BEV (arising from reduced wear on the gasoline engine) and lower energy costs (\$10 K versus \$3.5 K ICEV), although insurance costs were higher. The GHG emissions are higher than the solar-charged BEV option in Scenario 1, as the scenario involves use of an electrical grid. This finding is also congruent with previous research [59]. Both scenarios reinforce previous research showing that EVs can reduce GHGs [60] and have a lower TCO [7].

A significant concern of the consumer might be the residual value of the vehicle upon resell. Both scenarios illustrate that residual values are lower for BEV and PHEV. ICEV appear to retain their value much better. High-end BEVs have seen some improvement in this area with Tesla Model S holding its value better than any vehicle regardless of type [61].

Utility market changes are also consideration for purchasing of a vehicle, as they effect fuel-cost savings and thus the TCO [3]. By including forecasting models for various energy options, the simulation models these effects for inclusion in the analysis.
