Charging an Electric Vehicle (EV) at Home with Solar Panels: How Long Does It Take?

Much like the joke posing the question: 'If your car was plugged in the night of Jesus’ birth, it wouldn't be fully charged until today,' EV charging with solar panels isn't as straightforward as it might seem. Understanding the interplay between sun and solar panels can help you optimize your EV charging routine.

Understanding Solar Charging

Solar panels generate electricity from sunlight, which means they’re inactive during nighttime. Therefore, attempting to charge an EV solely during the night with solar panels is, to put it mildly, inefficient. It’s like trying to fill a car’s gas tank with a pump that isn't turned on.

Solar Charging During the Day

However, if you charge your EV when the sun is shining, you’re making the most of the solar power generated by the panels. For instance, a single 400W solar panel can generate 1 kWh in about 2.5 hours of full sunshine. Assuming the EV's battery has a capacity of 60 kWh, it would take approximately 150 hours to fully charge the battery using one solar panel.

Real-World Scenario

In a more realistic setting, a 4-mile-per-kWh EV, with a 11kW solar installation, can charge more effectively during daylight hours. If the solar panels receive their maximum power output (11kW) and the EV's charging system can absorb up to 7kW, the difference covers household consumption (up to 4kW) and some utility power. This means that the solar energy provides part of the charging, and the utility grid covers the rest.

Factors Influencing Charging Time

Several factors come into play, determining how long it takes to charge your EV at night with solar panels. These include:

The size of the solar panels The efficiency of the vehicle's charging system The amount of battery capacity in need of charging Weather conditions (cloud cover, snow, or lack of sunshine)

Charging with Sunlight or Cloud Cover?

Solar panels generate the least amount of electricity on cloudy days or during the night. If you need to charge your EV during these periods, your battery will still be partially topped up with the electricity stored by the panels during sunny times. However, relying on cloud-covered or night charging is not an ideal strategy for most users.

Utility Grid Backup

In case solar panels aren't generating enough power, you can rely on the utility grid. This combination of solar and grid power allows for more consistent charging. For example, if the car needs 7kW and the air conditioning system uses 10kW, the excess power will be sourced from the utility grid. Whether or not this mix counts as solar power depends on your metering system and local policies.

Financial Benefits of Solar Charging

Installing solar panels can reduce your electricity bills and carbon footprint. In many cases, excess solar power can be sold back to the grid for credits, which can be used later. In my case, I cover most of my household needs and even pay lower utility bills with my solar panels.

Conclusion

Understanding the limitations and benefits of solar-powered EV charging is crucial for maximizing efficiency and cost savings. By combining solar power with the utility grid, many homeowners can enjoy a more sustainable and cost-effective way to charge their electric vehicles.

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