Start with daily driving energy
A rated range is measured under a specified test cycle. It is not a promise of daily range on your road. Temperature, speed, climate control, terrain and driving style change energy demand. For repeat planning, use measured battery consumption per kilometre where available.
Take a synthetic car driving 60 km/day at 0.16 kWh/km measured at the battery. Driving consumes 9.6 kWh. At an illustrative 90% AC charging efficiency, wall energy is 9.6 ÷ 0.90 = 10.667 kWh/day.
If your consumption figure already comes from an AC wall meter, it already includes charging losses. Do not divide it by charging efficiency again. The planner’s vehicle presets label their range cycle, market and capacity basis; a real-world adjustment remains a scenario input.
Use the smallest applicable power limit
A 7.4 kW wallbox connected to a car that accepts 3.3 kW AC cannot charge that car at 7.4 kW. With at least 3.3 kW available at the site, the example needs 10.667 ÷ 3.3 = 3.23 hours at constant power.
| Effective AC power | Idealised charging time | Fits a 4-hour connection? |
|---|---|---|
| 2.0 kW | 5.33 h | No: about 2.667 kWh wall-energy shortfall |
| 3.3 kW | 3.23 h | Yes, under the stated assumptions |
| 7.4 kW | 1.44 h | Only if car and site both support 7.4 kW |
These are energy/power calculations. Charging taper, auxiliary consumption, interruptions and departure uncertainty can require additional time. AC wallbox ratings also depend on supply and phase configuration.
Count connected hours, not the whole night
If the car arrives at 22:00 and leaves at 06:00, the connection window is eight hours across midnight. But a cheap tariff from 01:00 to 03:00 provides only two cheap hours. At 3.3 kW, those hours supply 6.6 kWh, leaving 4.067 kWh to buy in another available period.
A lowest-cost schedule must still deliver the target energy before departure. If all charging is forced into the cheap window, the example misses its target. Inspect unmet-energy outputs before comparing costs.
Shared chargers add another constraint
Two cars requiring 10.667 kWh each need 21.333 kWh from the wall. Across four hours, the average aggregate requirement is 5.333 kW. A 4 kW site limit can deliver at most 16 kWh in that window, so the group is short by 5.333 kWh even with enough sockets.
This aggregate test is necessary but not sufficient. Each car also needs enough connection time, an available charger and its own acceptance limit. An average-power calculation cannot prove that a fleet schedule is feasible when arrivals and departures differ.
Keep the cost boundary visible
At an illustrative flat energy rate of ₹8/kWh, the single-car example costs 10.667 × 8 = ₹85.33/day, or ₹2,560 for 30 identical days. This excludes fixed charges, demand charges, subscriptions, taxes and charger ownership costs.
Run a slower-charging and higher-consumption case alongside the base case. Use the planning notebook for a quick energy/window check, then the EV planner for half-hour scheduling and tariff comparisons. Confirm vehicle specifications and tariffs against current primary sources before committing to equipment.
Sources and scope
- U.S. DOE Alternative Fuels Data Center: Charging at home ↗
General charging and home-supply considerations; U.S. installation rules are not Indian requirements. Vehicle, tariff and distance values above are synthetic, not product recommendations.
Reference links provide technical context; the worked examples and interpretation are specific to this guide. No external source certifies these tools.