Getting an electric vehicle (EV) like the Tata Nexon EV or Mahindra BE 6 is an exciting step towards sustainable mobility. However, charging your vehicle at home can significantly increase your electricity consumption and KSEB bill.

If you are planning to install solar panels to power your EV, you may be wondering whether a 3kW solar system is sufficient or a 5kW system is a better investment.

At TCM Solar, our team specializes in residential and commercial solar installations in Kerala. With our stated MNRE and ANERT certifications and KSEB empanelment, we manage the process from system design to installation and documentation through our in-house engineering and installation team.

In this guide, we compare 3kW and 5kW solar systems to help you choose the right capacity for your home, EV charging requirements, and long-term electricity savings.

1. How Much Electricity Do Your Home and EV Actually Consume?

Before choosing a solar system, it is important to estimate your total monthly electricity consumption. Your existing KSEB bill alone may not reflect your future requirements once you start charging an EV at home.

Household electricity consumption

A typical three-bedroom house with appliances such as a refrigerator, washing machine, lights, fans, and an air conditioner may consume approximately 150–200 units of electricity per month. Actual consumption depends on the number of appliances, usage patterns, and air-conditioning requirements.

Electric vehicle charging consumption

An EV’s electricity consumption depends on its battery efficiency, driving conditions, and charging losses. For a practical estimate, consider a vehicle that consumes approximately 1 unit of electricity for every 7 kilometres driven.

If you drive around 30–40 km per day, your monthly driving distance would be approximately 900–1,200 km.

At an average of 7 km per unit, this translates to roughly 130–170 units of electricity per month, excluding any additional charging losses.

Your combined monthly electricity requirement

Electricity usage	Estimated monthly consumption
Household appliances	150–200 units
EV charging	130–170 units
Total requirement	280–370 units

For planning purposes, a household with an EV may require approximately 350 units of electricity per month. Your actual requirement could be higher if you drive long distances or operate multiple air conditioners.

2. 3kW vs 5kW Solar System: Which Performs Better in Kerala?

Kerala receives useful solar irradiation throughout the year, but electricity generation varies with the season, rainfall, roof orientation, shading, and installation quality.

Let’s compare the two system sizes.

Option 1: 3kW Solar System – A Practical Choice for Lower Consumption

A properly installed 3kW rooftop solar system may generate approximately 300–400 units per month under favourable conditions, although output can be considerably lower during prolonged cloudy or rainy periods.

Advantages of a 3kW system:

• Lower initial installation cost compared with a 5kW system.
• Suitable for households with moderate electricity consumption.
• Can support EV charging when combined with efficient household energy use.
• May qualify for the maximum applicable central residential solar subsidy, subject to scheme eligibility.

What should you consider?

If your household consumes 180 units and your EV requires another 150 units, your combined demand is already around 330 units per month. A 3kW system may cover much of this demand, but there may be little surplus during periods of reduced solar generation.

A 3kW system is worth considering if your daily driving distance is limited, your household consumption is low, or your roof has space constraints.

Option 2: 5kW Solar System – More Capacity for EV Owners

A 5kW rooftop solar system may generate approximately 500–650 units per month under suitable conditions. Actual output depends on local weather, the system design, and site conditions.

For households that regularly charge an EV, this additional generation capacity provides more flexibility.

Advantages of a 5kW system:

• Greater electricity generation for household appliances and EV charging.
• More capacity to accommodate future electricity consumption.
• Better potential to offset higher consumption during periods of regular EV use.
• More flexibility when running air conditioners and other energy-intensive appliances.
• Potentially greater long-term savings when the additional generation is used effectively.

Why consider 5kW?

If your combined monthly consumption is around 350 units, a 5kW system may generate more electricity than you use over a typical month. This additional generation can help offset periods of lower production, subject to seasonal variation and applicable grid-settlement rules.

For households planning to add another EV, increase air-conditioning use, or accommodate other high-load appliances, a 5kW system may also offer useful additional capacity.

3kW vs 5kW: Quick Comparison

Feature	3kW Solar System	5kW Solar System
Indicative monthly generation	300–400 units	500–650 units
Best suited for	Moderate electricity consumption	Higher consumption with regular EV charging
Initial investment	Lower	Higher
Future expansion flexibility	More limited	Greater
Central residential subsidy	Up to the applicable eligible amount	Same maximum central subsidy as 3kW, subject to eligibility
Recommended for	Lower household and EV demand	Households seeking additional generation capacity

Note: These figures are indicative estimates, not guaranteed generation levels. A site assessment is necessary to estimate actual output.

3. How Does KSEB Net Metering Work for EV Charging?

One of the biggest advantages of a grid-connected rooftop solar system is the ability to exchange electricity with the grid under an approved net-metering arrangement.

Here is how the process generally works:

1. During the day: Your solar panels generate electricity. Your home consumes the electricity it needs, while eligible surplus energy can be exported to the grid.
2. During the night: Your solar panels stop generating electricity. Your home and EV draw electricity from the grid.
3. Energy accounting: Your meter records the relevant import and export figures, and the applicable settlement rules determine how those units are accounted for.

This arrangement can help you use daytime solar generation to offset electricity consumption at other times.

However, net metering should not be treated as a physical battery. Exported electricity is accounted for according to the applicable regulations, tariffs, settlement period, and connection approval. Your final KSEB bill may still include fixed charges, minimum charges, or other applicable components.

Important: A grid-tied solar inverter normally shuts down during a grid outage unless the system has specifically designed backup functionality. Standard grid-tied solar installations also do not automatically provide power during a power cut.

4. PM Surya Ghar Subsidy: What Should Kerala Homeowners Know?

The PM Surya Ghar: Muft Bijli Yojana offers central financial assistance for eligible residential rooftop solar installations.

Under the standard central subsidy structure applicable to residential consumers in Kerala, assistance is calculated based on eligible installed capacity and applicable scheme conditions.

For general residential consumers, the commonly applicable central subsidy structure is:

Eligible system capacity	Indicative central subsidy
1kW	₹30,000
2kW	₹60,000
3kW and above	₹78,000 maximum

A 5kW installation does not automatically qualify for a higher central subsidy than a 3kW installation under this standard structure. Eligibility, approved capacity, vendor requirements, and scheme rules must be verified before installation.

The final cost of your system will depend on the equipment selected, roof structure, installation complexity, and any additional electrical work.

Is a 5kW system financially worthwhile?

Even though the central subsidy generally caps at 3kW, a 5kW system may still be a sensible investment for an EV-owning household.

The key is to compare:

• The additional upfront cost of the 5kW system.
• The extra electricity it is expected to generate.
• The proportion of that electricity you can use or receive credit for.
• Your current electricity tariff and future consumption.
• Maintenance costs and the applicable grid-settlement rules.

Rather than choosing a larger system solely because it produces more electricity, calculate whether the additional capacity delivers enough financial benefit for your particular household.

5. A Real-World Example: A 5kW Solar Installation in Ernakulam

Consider a household in Ernakulam preparing for regular EV charging.

Illustrative project scenario

• System capacity: 5kW grid-tied rooftop solar system.
• Existing electricity bill: Approximately ₹3,000 every two months.
• EV usage: Around 40 km per day.
• Estimated solar generation: Approximately 580 units per month under suitable conditions.

With a 5kW system generating around 580 units in a particular month, the household may have enough solar generation to offset a substantial portion of its combined electricity consumption.

The actual savings depend on household demand, EV efficiency, seasonal generation, self-consumption, and the applicable KSEB billing arrangements.

A zero electricity bill should not be assumed in every case, since fixed charges and other billing components may remain payable.

Before publishing this section as a completed customer project, confirm the installation details, actual generation records, and bill savings with the project team. If these details are illustrative rather than documented, label the example accordingly.

6. Calculate Your Solar Requirements and Payback Period

Choosing between 3kW and 5kW becomes easier when you estimate your monthly electricity usage and compare the cost of each system.

Your calculation should consider:

• Average monthly KSEB electricity consumption.
• Daily EV driving distance.
• Estimated EV charging efficiency.
• Expected monthly solar generation.
• Total installation cost after eligible subsidy.
• Expected annual savings under the applicable billing arrangement.

A solar ROI calculator can help estimate the likely system size and payback period. However, the result should be based on actual installation quotations, local generation estimates, and applicable tariffs rather than a fixed payback promise.

7. Frequently Asked Questions

Which solar system is best for EV charging in Kerala?

A 5kW solar system is worth considering for households with regular EV charging and moderate-to-high household electricity consumption. A 3kW system may be sufficient for homes with lower consumption and limited daily driving. The best capacity depends on your total electricity requirement and available roof space.

Can a 3kW solar system run my house and charge my EV?

Yes, it can offset a significant portion of both household and EV charging consumption. However, a 3kW system may not generate enough electricity to cover all your requirements every month, particularly during periods of heavy rainfall or increased consumption.

Can I charge my EV at night using solar electricity?

Yes, you can draw grid electricity at night and use eligible daytime solar exports to offset consumption through an approved grid-settlement arrangement. The accounting and financial benefit depend on the applicable KSEB rules. Alternatively, a compatible battery system can store solar energy for later use.

Does a 5kW solar system receive a higher PM Surya Ghar subsidy than a 3kW system?

Under the standard central residential subsidy structure, the subsidy generally reaches its maximum of ₹78,000 at 3kW. A 5kW system does not automatically qualify for a higher central subsidy. Verify the latest scheme requirements before proceeding.

How many solar panels are required for a 5kW system?

The number depends on the wattage of the selected panels. For example, 10 panels rated at 500W each provide a total installed capacity of 5kW. The final panel count and layout depend on the equipment selected and available roof area.

Is battery storage necessary for EV charging with solar panels?

Not necessarily. A grid-connected system with an approved metering arrangement may be sufficient for many households. Battery storage is useful when backup power or greater energy independence is a priority, but it adds to the upfront cost.