The problem with charging an EV from the grid
An electric vehicle charger is an unusual electrical load. It is not like lighting or air conditioning, which draw a fairly steady amount of power for hours. A charger sits idle, then suddenly pulls a large block of power for twenty minutes, then goes quiet again. And the faster the charger, the sharper that block.
That shape is what makes EV charging expensive to run, and it is why solar and storage fit the problem so well. There are really two costs to attack: the price per unit of the electricity, and the demand charge you pay for the peak power your site draws. Solar attacks the first. A battery attacks both.
Demand charges: the bill line people forget
Most commercial and industrial connections in India are billed on two components. You pay for energy (every kWh you consume) and you pay a demand charge based on the highest power your site drew during the billing period, measured in kW or kVA. We explain the mechanics in detail in demand charges explained.
For a normal factory, the demand charge tracks the machinery. For a site with a fast charger, something more awkward happens: a single 60 kW DC charger, switched on while the rest of the site is already running, can push the recorded peak well above anything the business itself needs. That new peak then sets the demand charge for the entire month — even though the charger ran for a few minutes.
Worse, if the spike exceeds your sanctioned load (the capacity your DISCOM has contracted to supply), you are looking at penalties and, eventually, a connection upgrade — a slow, expensive process involving new transformers and cabling.
That 0.7-versus-1.3 spread is the single most useful fact for anyone designing a charging site. The regulation deliberately makes daytime energy cheap and evening energy dear. But the vehicles do not care about regulation — commuters plug in when they get home or when the shift ends, which is precisely when power costs the most. A battery is what reconciles the two.
How solar plus storage changes the economics
The logic runs in three steps:
- Solar cuts the energy price. A rooftop array at a charging site generates during exactly the hours the guidelines already price cheaply. Every unit you self-generate is a unit you neither buy nor pay network charges on.
- The battery moves that energy to when it is needed. Daytime solar is stored and discharged into the evening charging rush, so vehicles are effectively fuelled by midday sun rather than 1.3x-tariff grid power. This is the same Time-of-Day arbitrage that drives most commercial storage projects, just with cars at the end of it.
- The battery hides the spike. When a fast charger fires, the battery supplies the surge and the grid connection barely notices. This is peak shaving, and for a charging site it is often the larger saving of the two — it protects the demand charge and lets a modest sanctioned load support a charger that would otherwise demand an upgrade.
That last point deserves emphasis. Buffering a fast charger with storage is frequently the difference between installing it this quarter and waiting a year for a transformer. A 250 kWh cabinet sited next to the chargers can absorb the bursts that a small connection could never deliver directly.
Sizing it for a real site
The right combination depends on when your vehicles actually charge, and this is where sites get it wrong. Broadly:
| Site type | Charging pattern | What usually fits |
|---|---|---|
| Office or factory car park | Vehicles plug in through the working day | Solar-heavy; a small battery to buffer fast-charger bursts |
| Highway or urban fast-charge hub | Unpredictable arrivals, peaks in evening | Storage-heavy; battery buffers every session and cuts sanctioned load |
| Bus or fleet depot | Vehicles return and charge overnight | Storage-heavy; solar banked all day, discharged after dark |
| Retail or mall charging | Evening and weekend concentration | Balanced solar plus storage for the evening peak |
A fleet depot is the clearest case. The buses leave at dawn and return at dusk, so the rooftop generates all day into an empty yard. Without storage that solar is exported for a modest tariff and the depot then buys costly night power to recharge. With storage, the same energy fuels the fleet. A solar-plus-storage configuration is doing nothing more exotic than matching supply to demand.
What the policy support looks like
Public charging infrastructure has real central funding behind it. PM E-DRIVE, the Ministry of Heavy Industries scheme notified in 2024 with a total outlay of ₹10,900 crore, earmarks ₹2,000 crore specifically for public charging infrastructure — supporting roughly 72,000 charging points, including fast chargers for cars, buses and two- and three-wheelers, along national highway corridors and at high-traffic locations. In 2025 the government extended the scheme for charging infrastructure and commercial segments such as e-buses and e-trucks to 31 March 2028, though subsidies for smaller vehicle categories run on a shorter clock.
Eligibility is aimed largely at government ministries, central public sector enterprises, states and their agencies rather than private site owners directly, so a private operator’s route is usually through a state nodal agency or a state EV policy. State-level capital subsidies for chargers exist separately and vary widely.
What this means for you
If you are adding EV charging to a commercial site, resist the instinct to size everything around the charger’s nameplate rating. Start with two questions: when do the vehicles actually arrive, and what is my sanctioned load. If arrivals cluster in the evening, or if the charger would push you past your contracted capacity, a battery will usually pay for itself faster than extra solar — through avoided demand charges and an avoided connection upgrade, not just cheaper units. If vehicles charge through the working day, lead with solar and add a smaller battery purely to buffer the bursts.
The regulated 0.7x/1.3x tariff spread means the arbitrage is written into the rules, and it is unusually predictable as these things go. To see what the numbers look like for your charging profile and DISCOM tariff, run your site through our savings calculator or send us your load and charger specification and we will size it properly.
Policy and tariff snapshot as of August 2026. EV charging guidelines, service-charge caps, solar-hour windows, PM E-DRIVE eligibility and state subsidies are set by central and state notification and change frequently — verify the current terms with your DISCOM and state nodal agency before financial decisions.