Plug-in Hybrid Economy Calculator
EcologyCalculate fuel savings and CO₂ reduction from a plug-in hybrid vehicle vs a conventional car. Find annual savings and percentage of distance driven on electricity.
Annual Fuel Savings ($)
What is a PHEV Economy?
The Plug-in Hybrid Economy Calculator quantifies the annual fuel savings and CO₂ reduction you can expect by switching from a conventional petrol car to a plug-in hybrid electric vehicle (PHEV) on Indian roads. Enter your driving pattern, local electricity tariff, fuel price, and PHEV specifications, and the calculator tells you how much money you save each year, how many kilograms of CO₂ you avoid, and what percentage of your annual driving runs on electricity.
PHEVs occupy a practical middle ground in India's evolving vehicle market: they eliminate range anxiety while still delivering meaningful emission and cost reductions for drivers who charge regularly. This calculator makes that trade-off concrete and specific to your situation.
How to use this PHEV Economy calculator
Set your Annual Distance Driven (km) using the slider. This is your total vehicle use across the year — commuting, errands, intercity trips, and all other driving. If unsure, check your odometer readings from the past year or use 15,000 km as a starting point for typical Indian urban use.
Enter the Electric-only Range (km) of your PHEV. This figure is published in the vehicle's specification sheet — for example, 50 km for many mid-range PHEVs. It determines how much of each average trip runs on electricity.
Set the Electricity Cost per kWh (₹) to your applicable domestic tariff. Find this on your electricity bill under the applicable slab for your consumption level. Most urban residential consumers in India pay between ₹6 and ₹10/kWh in 2026.
Enter the Fuel Cost per Litre (₹) for petrol at your usual filling station. The default of ₹105 reflects mid-2026 metro prices; adjust for your city and grade of fuel.
Set the Conventional Car Fuel Economy (km/L) — the mileage of the petrol car you are comparing against or replacing. The default of 12 km/L suits a mid-size sedan. For a compact hatchback, use 15–18; for a large SUV, 8–10.
Enter the PHEV Electric Efficiency (km/kWh) from the vehicle's specifications. This is the distance the vehicle travels per kWh in electric mode — typically 5–7 km/kWh for Indian-market PHEVs. Check the manufacturer's ARAI or WLTP rating.
Read the results. Annual Fuel Savings is shown highlighted at the top. Below it, Annual CO₂ Saved and Percentage of Distance on Electric give you the environmental and operational breakdown. Adjust any input to model different scenarios in real time.
Formula & Methodology
The calculator uses an average trip distance of 20 km as the basis for determining the electric fraction of driving.
Electric fraction of driving
$$f_e = \min!\left(\frac{R_e}{20}, 1\right)$$
Where Rₑ is the electric-only range in km. If the electric range equals or exceeds the average trip, the electric fraction is capped at 1 (100%).
Annual electricity consumption (kWh)
$$E_{kWh} = \frac{f_e \times D}{\eta_e}$$
Where D is annual distance in km and ηₑ is PHEV electric efficiency in km/kWh.
Annual petrol consumption (litres)
$$P_L = \frac{(1 - f_e) \times D}{\text{kmpl}{\text{conv}}}$$
Where kmpl_conv is the conventional car fuel economy.
Annual petrol consumption for pure petrol car (litres)
$$P{L,\text{conv}} = \frac{D}{\text{kmpl}{\text{conv}}}$$
Annual fuel savings (₹)
$$S = \left(P{L,\text{conv}} \times C_f\right) - \left(E_{kWh} \times C_e + P_L \times C_f\right)$$
Where Cₑ = electricity cost per kWh (₹) and Cₓ = fuel cost per litre (₹).
Annual CO₂ saved (kg)
$$\Delta\text{CO}2 = \left(\frac{D}{\text{kmpl}{\text{conv}}} \times 2.31\right) - \left(E_{kWh} \times 0.82 + P_L \times 2.31\right)$$
Where 2.31 kg CO₂/litre is the emission factor for petrol combustion and 0.82 kg CO₂/kWh is the 2026 Indian grid emission factor.
Worked example: 15,000 km/year, 50 km electric range, ₹8/kWh electricity, ₹105/litre petrol, 12 km/L conventional car, 6 km/kWh PHEV efficiency.
- Electric fraction: min(50/20, 1) = 1.0 (all average trips covered electrically)
- Annual electricity: 1.0 × 15,000 / 6 = 2,500 kWh
- Annual petrol (PHEV): 0 × 15,000 / 12 = 0 litres
- Conventional car petrol: 15,000 / 12 = 1,250 litres
- Savings: (1,250 × 105) − (2,500 × 8 + 0) = ₹1,31,250 − ₹20,000 = ₹1,11,250/year
- CO₂ saved: (1,250 × 2.31) − (2,500 × 0.82 + 0) = 2,887.5 − 2,050 = 837.5 kg/year
India context: FAME-II incentives reduce the upfront purchase cost of eligible PHEVs, and several states offer additional road tax exemptions. Combined with the fuel savings modelled above, the total cost-of-ownership advantage over a five-year period can exceed ₹5 lakh for high-mileage city drivers.Frequently Asked Questions