The ability to charge an EV using your solar-generated electricity is a big appeal for those with rooftop solar. While charging with your solar-generated electricity can eliminate the EV’s ‘fuel’ costs in theory, it is not always easy. 

The article discusses the different options for Home Solar EV charging, analyzes solar charging options, determines how long it takes to charge an EV using solar, and addresses some of the problems associated with using rooftop solar and batteries to charge them. The article below describes how Vehicle-to-Load (V2L) technology can be used for backup power and off-grid power for those interested.

How to charge an EV at home using solar

It is relatively easy to charge an electric vehicle with your rooftop solar panels, but it depends on a number of factors, the most obvious of which is how big your solar panel is, the time of day, and the weather. The best way to charge your EV quickly using solar power alone is with a large solar system and a smart charger, which we will cover in greater detail below.

How easily an EV can be charged using solar depends on the following:

• Type of charger used – The speed of the charger can range between 2kW and 22kW, depending on the type of charger used
• The size of your solar system – Typical rooftop solar systems are between 5kW and 15kW
• EV battery level – What is the battery level of your EV, and how many kWh does it need to be charged?
• Distance travelled – Do you drive frequently, and what is the distance travelled?

Based on your driving distance and type of charger, we have built a free solar and EV charging calculator that helps you determine how much solar you require to charge an EV.

Solar home charging can be easy if you don’t drive much because you can use a portable plug-in charger (level 1) and solar system with a relatively small 5kW capacity. Even with a larger solar system, solar EV charging with a more powerful 7kW (level 2) charger can be challenging. A level 2 charger cannot be fully charged during cloudy or bad weather because solar panels will not generate enough power. There are several solar charging options available, including smart EV chargers, explained in the following section.

How many solar panels do you need to charge an EV

A solar array is required to charge electric vehicles in a much greater number than a typical household because of the high power consumption of EV chargers. This is a common question, and the answer varies for everyone depending on how far they drive and how often they charge. In order to supply daily power requirements throughout the year, an average household usually needs 6 to 8kW of solar power, or 14 to 18 solar panels.

As a result, an average household that charges electric vehicles regularly will need 10 to 12kW of solar power. A typical solar panel is around 50% smaller than the average solar panel.

The charging rate of an electric vehicle can be easily achieved with a small solar system (6 to 8kW) if it is a low-power 10 to 15A portable charger. It depends on how much energy is consumed daily and what the charge rate is.

EV battery capacity and driving range

It is important to understand EV battery capacity and range before we get into too much detail about chargers and charging rates. The size of the battery is measured in kilowatt-hours (kWh), and electric vehicles are available with a wide range of battery sizes, ranging from 24 kWh up to 100 kWh. There are generally 65kWh batteries on most common electric vehicles, which give them a driving range of around 350 km, depending on the conditions and how efficiently you drive. 

EVs with a capacity of about 5 to 8 kWh will have a driving range of approximately 5 to 8 km. According to real-world comparisons, lighter, more efficient EVs consume 12 kWh per 100 km (1 kWh = 8.2 km), while larger, more powerful EVs require up to 20 kWh per 100 km (1 kWh = 5 km). A typical electric vehicle consumes approximately:

• 16kWh of energy per 100 kilometers (1.0kWh = 5.8 km), or
• 26kWh of energy per 100 Miles (1.0kWh = 3.8 Miles)

Due to increased aerodynamic drag, driving at higher speeds reduces EV range. However, most of the cars have regenerative braking, which recovers much of the energy typically lost when braking to slow down. In city start-stop driving, regenerative braking is particularly beneficial, as it increases efficiency and reduces air pollution and brake dust.

Home EV Chargers

The most common EV charger in homes is either a level 1 portable charger or a level 2 wall-mounted charger. Due to the enormous power demands and cost of DC fast chargers, households are unable to install them. However, large commercial buildings can install DC fast chargers as they have the required power. Below are the three main types of home electric vehicle chargers:

• Portable plug-in (granny) chargers – 1.4kW to 3.6kW
• Single-phase home EV chargers – 3.3kW to 7.4kW
• Three-phase home EV chargers – 7.0kW to 22.0kW

1. Plug-in (socket) EV charger

Nissan Leaf plug-in electric vehicle charger with 10A capacity

There are several different types of electric vehicles on the market today, but the majority of them include a basic portable charger that can plug into anything with a 10A power outlet. These small, granny chargers can recharge an EV from fully charged in 12 to 36 hours, depending on the battery size and state of charge of the battery initially. It is estimated that most portable chargers draw around 2.2kW.

However, losses often limit their charging rate to 1.7kW to 2.0kW, increasing range by roughly 10km to 14km per hour. You can also purchase portable chargers with 15A power, which are cheaper and much faster to use, but require a dedicated 15A outlet to be installed in your house or garage.

• Power rating: 2.0kW (10A), or 3.2kW (15A)
• Charge rate: 12 km (7.5 miles) of range per hour
• Portable charger price range: $250 to $600

Charging from solar: An average residential solar system of 6kW produces two to three kW, allowing charging of electric vehicles using 10A plug-in portable chargers even when partly cloudy.

2. Single-phase Home EV chargers

EV charger (level 2) mounted on a wall in a standard home

A single phase Level 2 electric vehicle charger is available in a variety of options and designs and can be mounted on walls or posts. Most are rated at 32 Amp, equivalent to 7.4kW of power, and can provide a vehicle with a range of 40 to 50km per hour at the maximum charge rate.

As most chargers allow you to adjust the charging rate between 8A and 32A through a mobile app, in theory, you can only recharge your car for about an hour or two a day given that the average person drives less than 50km a day. Using a single-phase 7kW Wallbox charger set to maximum charging speed, an average EV can be fully charged in 8 to 11 hours (overnight).

• Power rating: adjustable from 2.0 to 7.2kW (32A)
• Charge rate: up to 45 km (28 miles) of range per hour
• Single-phase charger price range: $500 to $2400

Charging from solar:

An EV charger with a single-phase power supply (7kW) can be charged at full speed with a solar system rated at 10kW+ during good weather. If the charger is set to a lower charging rate of around 4kW, solar charging can be accomplished with a smaller 6kW system. However, a smart charger will dynamically adjust charging rate to match your solar output, so it’s the best option.

3. Three-phase Home EV chargers

In general, Level 2 home electric vehicle chargers come in the same shape as single-phase wall-mounted devices and are typically rated 32 Amps (per phase). However, due to having three supply phases, they can provide three times as much power as the single-phase version, which is roughly equivalent to 22kW of charging power. If the maximum charging rate is used, a vehicle will be capable of traveling 120-150 kilometers per hour. 

If you use a 3-phase Wallbox charger, you can fully recharge an average electric vehicle within 3 hours. However, it is important to mention that not all electric vehicles are compatible with 3-phase AC charging. AC charging speeds up to 22kW are not achievable with all EVs, which has a maximum capability of 7kW to 11kW single-phase.

• Power rating: adjustable from 3.6 to 22.0kW (32A 3-phase)
• Charge rate: up to 130 km (80 miles) of range per hour – compatible EV required
• Three-phase charger price range: $600 to $2500

Charging from solar: 

Even with a much larger 15kW+ solar system, charging an electric vehicle using only solar power (up to 22kW) can be challenging, especially during cloudy conditions. There are a few solutions, such as setting up a three-phase EV charger to charge at a lower rate (such as 12kW). However, a smart EV charger is a better option, since it is capable of automatically adapting the charge rate to match the solar output.

Fast Home DC Chargers – Direct Solar Charging

Most roadside charging stations use rapid DC chargers with level-3 capability, but smaller level-2 chargers are either unavailable or prohibitively expensive at home. It is about to change, however, with several inverter companies working on hybrid inverters that can charge solar DC systems quickly at home at a speed of up to 22 kW. Although this seems quite innovative, it is actually not a new technology technically. 

High-voltage batteries used in electric vehicles, such as those used in hybrid inverters, have been charged directly from solar power for many years with hybrid inverters. In addition to increasing efficiency and charging speed, direct DC charging bypasses the limitations of the car’s onboard charger and the home’s AC infrastructure. Sigenergy and SolarEdge both offer affordable Home DC chargers in the final stages of development.

• A SolarEdge DC charger can deliver up to 24 kW of DC fast charging, utilizing solar, batteries, or grid power simultaneously. With the charger, both 400 V and 800 V EV systems will be supported via a standard CCS connector, and, most importantly, it will be bidirectional, allowing the EV battery to be utilized as a backup energy storage solution whenever outages occur.
• SIGenergy SigenStor hybrid EV charging systems range in capacity from 5kW to 25kW and can be installed in single-phase or three-phase configurations. A maximum capacity of 48kWh is achieved by stacking five and eight-kWh modules up to six units high, providing a scalable battery capacity. In addition to being V2H ready to support bidirectional EV charging, the Sigenstor supports DC EV fast charging at capacities of 12.5kW or 25kW with an optional EV charging unit.

Already have solar installed?

Solar systems come with an energy (CT) meter, and solar apps that provide information on solar generation and household consumption if you already have one.

It makes sense to use the same solar inverter charger as your electric vehicle charger if this is the case and allows you to easily set up a smart charger for your electric vehicle. In the same way, hybrids (battery storage) already come with energy meters, so they can also be charged using smart EV chargers. It’s important to note that they require you to use the same EV charger brand as your solar inverter, for example Fimer, SolarEdge, Enphase, Fronius, or Sungrow.

Smart EV Chargers

There are a variety of smart EV charger modes that optimize when and how your electric vehicle is charged. There are a number of charging options, including scheduled charging, boost charging and solar-only charging, which allows you to charge during off-peak times.

A smart EV charger can be used to maximize the use of solar on your rooftop if you have it installed. By monitoring your solar generation and diverting it to your EV charger instead of exporting it to the grid, these smart charge controllers can help you save money. By charging your EV this way, you won’t have to use power from the grid during bad weather or intermittent power outages.

How do smart EV chargers work

In most cases, a standard home electric vehicle charger draws between 3.5kW and 7.4kW, depending on the charger and its settings. When charging via rooftop solar, the amount of energy generated may be much lower, especially during bad weather.

To overcome this problem, smart EV chargers use an energy metering device called a CT clamp which monitors energy flow to and from the grid near the main electrical supply. When it detects excess solar energy flowing into the grid from your solar, it will charge your EV accordingly.

This can, however, fluctuate constantly due to changes in power consumption and solar generation, so smart electric vehicle chargers continuously adjust

How long does it take to charge an EV using solar?

Generally, it takes a long sunny day for a standard rooftop solar system to charge an average EV from 30 to 80% using a standard 6.5kW solar system. This question is open-ended due to the battery capacity and size of the solar system.

In colder, less sunny locations, having more solar power at home is obviously a good thing when charging an electric vehicle. Solar power can be an extremely effective way to charge an electric vehicle as long as you are home during the day, as long as you do not drive more than 80 kilometers per day.

If you are home during the day, solar can be a relatively straightforward way to charge an electric vehicle.

Using solar systems of the following sizes, the average daily charge time is as follows:

• 6.5kW solar system = 8 hours to charge from 20 to 80% (Hyundai Kona 64kWh)
• 10kW solar system = 5 hours to charge from 20 to 80% (Hyundai Kona 64kWh)

A battery’s actual charge time can vary significantly depending on its condition, the type of EV charger, and the weather. An EV can be charged up to 80% in seven to nine hours with a larger 10kW rooftop solar array and a 7kW Type 2 charger on a sunny day, while a 15kW solar array and a more powerful 3-phase charger can be charged in five hours.

It is often assumed that the household load will be low and the weather will be sunny during these charging times, but things aren’t always the same. EV smart chargers can help you avoid paying for grid power to charge your EV at home if you want to avoid paying for grid power.

Here are the average daily charge rates for solar systems of the following sizes

• 6.5kW solar system = 4.0kWh per hour = 22 km (14 miles) of range per hour *
• 10kW solar system = 7.5kWh per hour = 36 km or (22 miles) of range per hour *

This information is based on a measurement made in Sydney, Australia, which is comparable to Spain or Southern California.

EV Charging Efficiency

Charge efficiency of a typical electric vehicle when using a household charger depends on several factors, such as the charge speed, ambient temperature, battery temperature, charging cable length, and the efficiency of the vehicle’s power converter (AC to DC charger).

There are several reasons why temperature can affect charging efficiency. A vehicle’s battery cooling system may need to operate while charging at a high ambient temperature, whereas a battery heating system may need to operate at a low temperature below 5oC. As EVs charge at sub-zero temperatures, the rate may be drastically reduced until the cells have warmed, even without heating. The electrical resistance of any charger will increase slightly in high temperatures, resulting in slightly less efficiency.

EV Charging Test Results

Cleaning Energy Reviews tested the charging efficiency of a small portable 10A charger and a 7kW wallbox charger at various charging rates on a BYD Atto 3 electric vehicle. Based on the results shown in the chart below, a portable 10A charger charges at a rate almost 10% lower than a dedicated EV charger due to the lower charging rate and the loss of energy in the charging cable, which results in almost 10% lower charging efficiency. When portable chargers are connected to long extension leads, charge losses are also amplified.

EV Charging losses explained

As the electrical current travels through the extension cable, cable losses result from resistance and voltage drop. Three main factors determine the amount of voltage drop:

• Charging current – As charging speeds (currents) increase, voltage drops also increase.
• Cable length – Longer cables are more likely to drop voltage and lose power.
• Cable size – When the cable size (copper core size) is larger, cable losses are less likely to occur.

Portable EV chargers with long leads

The resistance of cables increases with higher temperatures, resulting in a voltage drop and a reduction in power, and the length of cables and higher currents result in higher power losses. According to the real-world test results shown below utilizing a BYD electric vehicle, there can be significant losses associated with cables, particularly long extension leads used with portable chargers. High temperatures can also amplify the losses, particularly if the charging cable and extension leads are exposed to the sun (on concrete).

If you are using a portable electric vehicle charger, you should use a shorter extension lead to increase charging efficiency. If you need a longer cable, you should use a larger size cable. Generally, 10A extension leads use 1.0mm2 copper cores, while 15A extension leads use 1.5mm2 copper cores. When you use a portable granny charger and need a long extension lead, it is better to choose an outlet with a higher current 15A and a larger 1.5mm cable.

BYD Atto 3 Electric Vehicle Charging Efficiency Test Results – Testing the charging efficiency of a portable 10A charger with different length extension leads and a wall-mounted EV charger at different charging rates.

Low charge rates = Lower efficiency

Electric vehicles operate more efficiently when they work close to their rated power output, and inverters and chargers are no exception. The built-in charger of an electric vehicle converts AC power from the grid to high-voltage DC power. Power conversion (via transistors) is necessary for this process, as well as the powering of auxiliary controls such as battery cell balancing and temperature control.

A wallbox charger rated at 7kW will suffer significant losses if it is charged at only 2kW. Charging at 50% or higher of the charger’s rating will result in higher efficiency. As explained previously, higher charging rates can also result in higher cable losses when using portable chargers with extension leads, so it is important to maintain a balance between the cable length and charge rate when using portable chargers with extension leads.

Off-grid solar EV charging & challenges

There are several reasons why charging an electric vehicle with a typical home off-grid solar system may prove challenging, the most obvious being the limited amount of energy available during the day, particularly during bad weather. In addition to the limited charging window for electric vehicles, solar power is the best way to charge them. 

In most cases, overnight charging involves running a backup generator, or reducing the charging time or rate to only use a portion of the battery off-grid. EV batteries have a very large capacity compared to residential off-grid systems, so if left charging overnight, it would drain the battery. In contrast, an average electric vehicle has a 65kWh battery, while a typical off-grid home may have only a 30kWh battery. 

Assuming that a 7kW home EV charger is not monitored or controlled properly, the high current consumption rate could drain an off-grid battery in 5 hours, leaving the system shutdown or needing to run the backup generator for an extended period of time.

Off-grid charging with battery management and control features is now available with the Victron EV Charger.

Off-grid EV Chargers and Solutions

Due to the lack of grid export, most smart EV chargers cannot be used in an off-grid system while charging using solar. This is especially true when using AC-coupled off-grid systems, as this can be extremely challenging to set up. 

The good news is that there are some simple solutions; most regular electric vehicle chargers can be used in an off-grid system as long as you reduce the charging rate to a lower level (between 3 and 4 kW) and manage consumption to avoid overcharging.

A modern off-grid system can be programmed to activate relays (control circuits) to keep batteries fully charged as well as reduce the risk of battery drain. Simple timers can be used to achieve this as well as smart timing systems for preventing battery drain.

The Victron Energy company currently offers just one dedicated off-grid electric vehicle charger. As a leading provider of off-grid power equipment, Victron has developed a smart EV charger with off-grid capabilities that prevents the household battery from being discharged below a predetermined level. The charger is, however, only compatible with Victron off-grid systems containing Victron GX devices (smart control hubs). 

Charge HQ – Smart charging using OPCC

An intelligent app-based control system that integrates with existing solar panels to charge electric vehicles is a recent technology. Inverters like Fronius, SolarEdge, Tesla, Sungrow, and Tesla, as well as energy monitoring platforms like Solar Analytics, can be used with the software developed by Charge HQ, which is compatible with a variety of popular energy storage systems and inverters.

If you have an electric vehicle or a home charger that is capable of charging your electric vehicle remotely, Charge HQ will be able to function.

Depending on your choice, it can either talk directly to your vehicle or your home charger. It is important, however, that the EV charger is compatible with the Open Charge Point Protocol (OCPP) and supports external power control.

The system can start charging when there is enough solar and stop charging when the solar power is below the set charge rate if it does not support power control. As part of the Internet of Things (IoT), EV chargers that are compatible with OPCC can also be integrated.

Bidirectional chargers – V2G & V2H

It is expected that vehicle-to-grid or V2G will become more popular in the future, using what is called a bidirectional charger. EV chargers normally send energy in one direction during charging, but bidirectional chargers allow energy to flow both ways from your electric vehicle. It is possible, on the other hand, to use a bidirectional charger to power your home or contribute to the electric grid balance during times of high demand, if required.

It is also an emerging technology which is called vehicle-to-home (V2H). Using solar energy, this technology can also be used to power a home nearby allowing the EV to function as a large household battery.

Bidirectional chargers can be used to provide backup power from an EV using Vehicle to Grid technology.

A few EVs, including the latest Nissan Leaf, are V2G compatible, and only a few are capable of accepting two-way charging. We can tell you more about bidirectional chargers in our detailed article on bidirectional chargers that this technology will be a game-changer in the next few years and can offer a range of services, from powering your home to storing extra solar power.

Vehicle-to-Load – V2L

The vehicle-to-load technology in EVs allows electric appliances to be powered directly by the vehicle’s standard (10A) power outlets and is simpler than the bidirectional chargers found in most EVs. A backup power supply is provided by EVs equipped with V2L technology in case of a blackout or emergency if they can provide AC power.

A fully charged EV could, theoretically, supply a typical household for several days without any interruptions, given that the average EV has a 60kWh battery. In addition to being useful for topping-up other electric vehicles with flat batteries, V2L can also be used to recharge other electric vehicles.

EV charging using a home battery.

A home battery system can provide 80km of driving range if you can use the total capacity of the battery for charging your EV if you are away most of the day. Generally, 10kWh home battery systems can provide up to 80km of driving range, if the total battery capacity is used for charging. Due to household consumption requirements, only half of the battery may be available, resulting in a driving range of 30 to 40 km.

The majority of the population (who live in cities) drives short distances on average, so this might be a suitable option. SolarEdge inverter EV charger is an excellent solution for drivers who travel long distances and have larger batteries or off-peak charging requirements. It helps manage and optimize your EV charging process by utilizing solar and battery storage.

Single-Phase Vs 3-Phase grid supply

Typical residential grid connections come in two varieties, single-phase and 3-phase. Single-phase connections offer a maximum power output of 20kW or 80A, whereas 3-phase connections can provide a maximum power output of 45kW (3 x 63A).

Home electricity is typically supplied to homes by the electricity grid from 12kW to 20kW. The maximum electricity supplied to a home by the electricity grid is typically 50A to 80A. A full grid capacity cannot be utilized when charging an EV, or you won’t be able to use any other appliances simultaneously. You would trip the grid supply switch if you used a toaster or microwave every time. Due to this, single-phase electric car chargers are usually limited to 32A or 7kW.

This isn’t an issue unless you’re looking for a fast charger. In order to enable higher charging rates, an electric vehicle charger with a load-balancing function can monitor household consumption and adjust charging rates accordingly.

It is also advisable to use smart load-balancing EV chargers if you are planning to install multiple level-2 electric vehicle chargers, as this could overload the commercial grid supply.

Frequently Asked Questions

Can I charge EV directly from solar panels?

I believe that solar power can absolutely be used to charge the batteries of electric cars. Solar panels already provide power to your phones, devices, and appliances, so take this into consideration: You already harness the sun’s power to charge your phone, laptop, and television.

How many solar panels do I need to charge an EV?

Consequently, you will need 12 solar panels of standard efficiency to charge your electric vehicle. If, on the other hand, you drive fewer than 39 miles per day and own more efficient solar panels, you will need fewer than 12 panels to charge your electric vehicle. The long-term benefits of investing in solar panels that are of high quality and efficiency are numerous.

How much does it cost to charge an electric car at home with solar panels?

A solar system installation in California costs on average $20,498. You’ll need about eight additional solar panels, costing about $1,480, if you plan to charge an electric vehicle with your solar system, bringing the total cost of installation to about $21,978 if you plan to do so.

How long would it take to charge an EV with solar?

If an EV is driven by an average EV driver each day, about 10% of its full charge will be used. In a country that receives 6.02 hours of peak sunshine per day, it would therefore take about 2.81 hours of solar EV charging to replenish this charge using an average solar array.