A Vidyutpath Charging 50 kW charger costs Rs 15 lakh, buys power at Rs 9 a unit and sells at Rs 18, pays a 10% site fee and Rs 1 lakh a year of maintenance. What daily utilisation gives a five-year simple payback?

About 152 kWh a day, roughly 3.0 hours at full 50 kW, a utilisation of about 13%. Each kWh earns Rs 7.20 after power and the site fee. A five-year payback needs Rs 3 lakh a year plus Rs 1 lakh of maintenance, so Rs 4 lakh of margin, about 55,556 kWh a year. Payback is very sensitive below this: at two hours a day it stretches to 9.2 years.

Start with the margin per kWh, because everything scales from it. The driver pays Rs 18, the site owner takes 10%, Rs 1.80, and the power costs Rs 9, so each kWh leaves Rs 7.20. A tea stall works the same way: the price of a cup less milk, tea and the rent share is what is left to pay off the stove. Fixed costs come next: Rs 1 lakh of maintenance a year must be covered before a rupee goes toward the Rs 15 lakh charger.

A five-year simple paybackThe time it takes for the cash an investment generates to add up to what it cost, ignoring the time value of money. on Rs 15 lakh needs Rs 3 lakh of cash a year. Add Rs 1 lakh of maintenance and the charger must earn Rs 4 lakh of margin a year. Rs 4 lakh divided by Rs 7.20 is about 55,556 kWh a year, or 152 kWh a day: 3.04 hours at the full 50 kW, about 12.7% of the day.

Very, because the fixed maintenance cost is paid whatever the usage. Each hour a day of full-power use earns about Rs 1.31 lakh a year. At two hours a day payback is 9.2 years; at four hours it is 3.5 years; at one hour it is about 48 years, longer than the charger will last. The curve is steep on the left: the difference between a good site and a poor one is not a few months of payback but whether the charger ever earns back its cost.

Size the site before spending the capex: count the cars that stop for 30 minutes or more, not the cars that pass. 152 kWh a day is about five to six cars each taking 25 to 30 kWh, which a highway stop with long dwell times can deliver and a mall car park with one-hour visits and home-charging owners may not. Three caveats belong in the answer. A 50 kW charger rarely delivers 50 kW for a whole session, because many cars draw less as the battery fills, so the real hours needed are higher than 3.0. Utilisation usually starts low and rises as more electric cars arrive, so the first years are the weakest. And a simple payback ignores the time value of money, which a discounted payback or NPV would add.