Enjoy this one as it gets technical and "stuff". Wayne Gerdes – CleanMPG – Feb. 24, 2017 2017 Hyundai Ioniq PHEV-27 - Pricing and availability TBA later this year. An estimated 27 miles of all-electric range is part of the bargain. MPG and MPGe results will be made available later this year as well. The 2017 Hyundai Ioniq Plug-in Hybrid incorporates a direct-injected, 104 hp and 109 lb-ft of torque, 1.6L Atkinson-cycle I4 with a thermodynamic efficiency of 40 percent. Along with a clutched 60 hp permanent magnet synchronous electric motor powered by a 8.9 kWh Li-Ion battery allowing an estimated 27 miles all-electric range (AER), the package is mated to a very quick-shifting six-speed dual clutch transmission. The Ioniq PHEV design selected the dual-clutch transmission not only for its superior energy transfer from input to output shaft but also to make it feel vastly different from the Continuously Variable Transmissions used in all other PHEVs. The Battery - Electric power storage for the PHEV is courtesy of a non-polymer lithium-ion battery that is 20 percent lighter than standard prismatic cell format Li-Ion batteries. This chemistry is said to provide lower memory sensitivity, excellent charge and discharge efficiency, outstanding maximum output, and better longevity. To go along with this intro, I received an interesting question regarding an upcoming event and I thought many here would be interested in the reply. I scrubbed some of the details as it is under an NDA but this may provide novices with more information about what a Plug-in Hybrid (PHEV) is and is not with regards to how its efficiency can and is calculated. 2018 Hyundai Ioniq PHEV-27 How is the fuel efficiency different in a plug in hybrid car compared to a regular hybrid car? Good question and a tough one at that. A Hybrid is relatively simple as you know. A driver covers a given distance on a given amount of gasoline or diesel providing the mpgUS, mpgIMP, L/100 km, or km/L end result. PHEV efficiency is not as clear cut. The Plug-In Hybrid (PHEV) is a very likely candidate to make up a very large percentage of our mobility future. The shorter range every day commute can be completed on renewable electric power while the long distance personal enjoyment or errand drive is covered with 5-minute refuels and very efficiently on gasoline. To your point directly, the PHEV is a mix of efficiencies and can be infinitely complicated. For example, some drivers try to drive their PHEV almost exclusively as an electric car with the car forcing almost a tank of fuel to be consumed once per year. Those drivers have an MPG rating in the hundreds or thousands of miles per gallon (mpg) not including the electricity consumption in that result. These type of people should have purchased a Battery electric instead. 2017 Chevrolet Volt PHEV-53 EPA rated at 43/42/42 mpgUS city/highway/combined and 53 miles on the plug. Others rarely plug-in their PHEV cars and instead rely on the convenience of filling up at the gasoline pump while receiving the financial benefits of the PHEV purchase and efficiency benefits of a pure Hybrid car. Most PHEV owners however actually use a mix of the two efficient driving scenarios – gasoline hybrid and pure electric driving – with a single daily charge at home covering more than half of the daily commute estimated at 43 miles. Commuting accounts for ~ 10,500 miles/year of the approximately 13,500 miles/year that the typical American drives. PHEV Drivers Consumption and Efficiency Case Study I am going to use the 2017 Toyota Prius Prime because it has the easiest to calculate electric efficiency with a 25 kWh/100 rating while on the plug. Under the above scenario, a typical American’s mobility needs while driving a 2017 Toyota Prius Prime PHEV-25 could include a 43-mile avg. daily commute for 5-days a week and 49 weeks per year plus 60 miles of errand/vacation travel on average traveled after work and each weekend. 2017 Toyota Prius Prime PHEV-25 EPA rated at 55/53/54 mpgUS city/highway/combined and 25 miles on the plug. The 2017 Toyota Prius Prime PHEV is rated for 25 miles of electric range from a full charge and has an 11.3 gallon fuel tank capacity. On the typical 43-mile RT commute, 25 miles would be covered by the electric drivetrain and 18 miles would be covered from the gasoline drivetrain as a hybrid car for the daily commute. An additional 60 miles per week to meet the 13,750 mile yearly driver miles total would cover after work and weekend errands plus longer distance vacation travel. I would estimate a single 25 mile electric charge on the weekend and the other 35 miles on gasoline covering these after work errands, weekend errands, and vacation travel. Together, this typical American driver would drive and consume the following in his 2017 Toyota Prius Prime PHEV-25: 150 miles on electricity at its EPA rated 25 kWh/100 miles or 37.5 kW 125 miles on gasoline at its EPA rated 54 mpgUS or 2.31 gallons MPG - If efficiency was solely based on the gasoline consumed over the distance traveled, the Prius Prime PHEV-25 would have achieved 275 miles on 2.31 gallons or 119.0 mpgUS. This is a very unrealistic way to calculate the cumulative mpg. There is a problem with this direct calculation not apparent in the discussion. A gallon of gasoline can be equated to 120 MJ of energy but it takes approximately 60 additional MJ of energy to extract, pump, and refine the raw oil to gasoline and transport it to the fuel station. I used the fact that 19.6 lbs of CO2 is emitted when consuming a gallon of gasoline through an internal combustion engine (downstream) vs. the upstream emissions of approximately 10 lbs off CO2 emitted to get create a gallon of gasoline and move it to the pump when calculating the well to wheel efficiency. MPG and kWh/mi - If the gasoline and electric driving efficiency were separated, the efficiency would be based on their respective fuels. In this case the efficiency would be 54 mpgUS on gasoline AND 25 kWh/100 miles. I believe this is the best way to calculate efficiency because it keeps the two vastly different fuel sources and their vastly different efficiency (upstream to downstream) measurements separate. MPGe - If efficiency was instead based on a combination of both “fuel sources” as an MPGe result, 120 MJ or 33.7 kWh of electricity = 1 gallon of gasoline. In the case of the Prius Prime driving 275 miles/week, 150 miles on electricity and 125 miles on gasoline similar to what the average American would/could/should drive, we would have the following: 37.5 kW * (1 gallon/33.7 kWh) = 1.11 “gallons of gasoline energy” consumed allowing 150 miles of driving in the case above. 2.31 gallons of gasoline was consumed allowing 125 miles of driving in the case above. Cumulatively, the Prius Prime traveled 275 miles/(1.11 gallons equivalent + 2.31 gallons) equating to 80.41 MPGe. The problem with the MPGe calculation imho is this. A gallon of non-ethanol laced gasoline contains just over 120 MJ or 33.3 kWh of energy within. However, to generate a kWh of energy via a coal, NG, or Nuclear plant, the input heat source to kWh output is only 30 to 40 percent efficient. Meaning the energy content calculation is even further off than that of gasolines energy consumed to produce a gallon of gasoline discussed above. In the creation of a kW of energy, a majority amount of low quality waste heat is generated and discarded. Between 60 and 70 percent actually. This is why I believe the separation of the two "fuel" sources is the most accurate way to calculate the efficiency of a given PHEV. The upstream to downstream inefficiencies of each "fuel" are contained within their respective efficiency calculations. 2017 Ford Fusion Energi PHEV-22 EPA rated at 43/41/42 mpgUS city/highway/combined and 22 miles on the plug. There are additional variables in the above calculations that in this single case, look at the average of the average. For one, most Hybrid and Plug-In Hybrid drivers have much longer commutes than the average American. Well over 15,000 miles per year on average. In this case, gasoline consumption would increase significantly while electric consumption would drop in concert. A 70 mile daily RT commute would be covered by 25 miles on electric and 45 miles on electric. I could describe an infinite number of scenarios but hopefully this write-up provides some insight as to the typical American PHEV owner.