Home EV Charging and Rooftop Solar: Planning Ahead

Why EVs and rooftop solar go together

Electric two-wheelers, three-wheelers and cars are becoming a more common sight in the towns of eastern Uttar Pradesh. For an owner, the attraction is a low running cost per kilometre, compared with petrol or diesel. When the vehicle is charged from your own rooftop solar, the cost per kilometre can fall further, because the energy comes from a system you have already paid for, with very low running cost.

The two also fit together in practice. A vehicle is a battery on wheels, and a home with solar often has surplus power in the middle of the day. If the vehicle is at home during those hours, charging it uses that surplus directly. Even if it is parked at night, the arrangement still works through the grid and net metering, with some care about settlement rules.

This guide is general information for households planning an electric vehicle, whether they already have solar or are installing it. Vehicle specifications differ, and we do not recommend any brand. Check the maker's figures and speak to a qualified electrician about the charging circuit.

Step 1: Estimate the extra units per day

The key number is how much energy your vehicle uses per kilometre. Makers publish a figure, and real-world use is often somewhat higher than the claim, especially in hot weather, with air conditioning and with heavy loads. Multiply the energy per kilometre by the distance you drive per day, and add a margin of about 10 percent for charging losses, since not all the energy from the socket reaches the battery.

The table below shows illustrative values only. They are assumed numbers to show the method. Replace them with your vehicle's figures.

Step 2: Convert it into solar capacity

As a rough guide, a kilowatt of rooftop solar in Uttar Pradesh produces around 4 to 5 units per day on average across the year. If the small car in the example needs about 5 units a day, that is roughly one extra kilowatt of solar to cover it on an average day. The scooter needs a small fraction of a kilowatt. A larger car doing longer trips needs correspondingly more.

Add this to the capacity you need for your home. If your house already uses 10 units a day and you add a car that uses 5, your total is 15 units, and a system of roughly 3.5 kW would cover it on an average day, depending on shade and season. Our article on how much solar you need explains how to start from your bills. Remember that your roof space may limit the size, and our roof assessment checklist helps you check it.

Generation is lower in the monsoon and winter. If you want most of your charging covered by solar all year round, size with a margin, or accept that in some months grid power will fill the gap.

Daytime charging and night charging

If your vehicle is parked at home during the day, for example because you work from home, run a business there or have a second vehicle, you can set the charger to run in the midday hours. The car then uses solar power directly, which is the cheapest and most efficient route. Some chargers and apps let you set a timer, and some smart chargers can adjust to follow solar surplus.

Most people commute, so their vehicle charges overnight. In that case, the energy comes from the grid, and net metering balances it against the surplus you exported during the day. Over a billing period, the net units matter, though settlement rules, any time-of-day tariffs and the treatment of unused credit are set by the regulator and can change. Check the current terms with your DISCOM and read our articles on net metering and on how credits appear on your bill.

Without a battery, you cannot store midday solar in your house for night charging. The vehicle's own battery is the cheapest store, so charge in the day when you can. Some households with a hybrid battery system also use it to offset evening loads, but a battery large enough to charge a car is costly and rarely worth it for this purpose alone.

Charger type, wiring and protection

A charger is a heavy electrical load that may run for hours at a time, so wiring quality matters. Slow charging from a normal socket is possible for scooters and some small cars, but a household socket and old wiring were not designed for hours of continuous high current. Poor connections and undersized wires can overheat and cause fires.

A dedicated circuit, with a properly rated cable, a suitable breaker, earthing and, where needed, a residual current device, is the safe approach. Wall-mounted AC chargers for homes commonly deliver a few kilowatts, and the rating you choose should match your vehicle's onboard charger and your electrical supply. Ask a qualified electrician to design and install it, and use equipment that meets Indian safety standards.

Place the charger where it is protected from rain, direct sun and mechanical damage, and where the cable can reach the vehicle without being a trip hazard. Keep it away from flammable materials. Our guide on earthing and safety explains why proper earthing matters for any heavy load.

• Use a dedicated circuit with a correctly rated cable and breaker.
• Make sure earthing is good and protective devices are fitted.
• Match the charger rating to your vehicle and your supply.
• Do not use extension cords or worn sockets for long charging sessions.
• Have the work done and checked by a qualified electrician.

Sanctioned load and approvals

A home charger adds to your peak load. A 3 kW charger running along with an air conditioner and a geyser can push your demand above your sanctioned load, which may lead to a higher bill or a notice from the DISCOM. Check your sanctioned load against your highest expected total use, and apply for a load increase if needed. It is a separate request with its own fee and timeline, so plan for it.

Also check the rules in your housing society or building. Charging points in shared buildings may need permission from the association, and wiring through common areas needs approval. If you rent, you need the owner's written consent before installing a charger or changing the wiring.

Check whether special EV tariffs or schemes exist in your area at present. Rules on EV charging tariffs and incentives are decided by the regulator and governments and change over time, so confirm on official sources before you plan around them.

Do not oversize blindly

A common temptation is to install a very large solar system just in case you buy an electric car later. This can lock up money for years, and net metering rules mean that large unused exports may not be worth as much as the units you buy. A more careful approach is to size for your present use plus the vehicle you actually plan to buy within the next year or so.

You can plan for a later vehicle without paying for capacity you may not use soon. Ask the installer to leave roof space for extra panels, choose an inverter and wiring that can take a later expansion, and check that the sanctioned load and meter arrangement allow it. This costs little now and avoids rework later.

Questions to ask your installer and electrician

If you plan an electric vehicle, say so at the first conversation. A good installer will ask about the vehicle, the daily distance, when it will be at home and where the charger will go. Our article on air conditioners and heavy appliances describes other loads that affect system size.

For a site visit and a written estimate that includes your future vehicle, use the quotation form on our home page and we will call you back.

• What extra units per day have you assumed for the vehicle, and how did you calculate them?
• Will the inverter, wiring and roof space allow a later expansion?
• Is my sanctioned load enough, and what is the process to raise it?
• Who will install and certify the charging circuit?
• How will charging time affect net metering for my home?