7kW EV charger: Why is it the mainstream choice for home charging?

Among the various power levels of AC chargers, 7 kW EV chargers have become the first choice for many home users and private charging sites because of their excellent balance between charging speed, installation convenience, cost-effectiveness, and vehicle compatibility. If you are considering buying a home electric vehicle charger, or are curious about 7 kW EV chargers, this article will provide you with all the information you need to help you decide whether it is the best choice for you.

What is a 7kW EV Charger?

To understand the 7 kW charger, you first need to understand the charging levels of electric vehicles. Currently, the mainstream electric vehicle charging methods are divided into three categories:

1. Level 1 Charging: Use the charging cable that comes with the vehicle to connect directly to a standard household 120 volt (V) (North America) or 220-240V (other regions) wall socket. The power is usually between 1 kW and 2.4 kW, and the charging speed is very slow, which is suitable for replenishing a small amount of power or for emergency use.
2. Level 2 Charging: Use dedicated charging equipment (charging pile or wall-mounted charging box) to connect to a higher voltage line, usually 208V, 240V (single phase) or 380V, 400V (three phase). The power range of Level 2 charging is wide, ranging from 3.5 kW to 22 kW. 7 kW is a very common and representative power level in Level 2 charging.
3. Level 3 Charging/DC Fast Charging: Uses dedicated DC charging piles to directly provide DC power to the vehicle battery. The power is very high, usually ranging from 50 kW to more than 350 kW. Mainly deployed in public charging stations for fast energy replenishment, not suitable for home installation.

Therefore, the 7kW electric vehicle charger is an AC Level 2 charging device . It needs to be installed on an independent circuit with a higher voltage (usually 220-240V single-phase). The charger itself transmits AC power from the grid to the vehicle, and the "onboard charger" inside the vehicle is responsible for converting AC power to DC and charging the battery.

How is 7 kW EV charging achieved?

A 7 kW AC charger is typically powered by connecting to a standard 220-240 volt (V) single-phase power source.

The calculation formula of AC power (P) is: P=V×I×PF (V is voltage, I is current, PF is power factor, usually close to 1)

To achieve 7 kW (7000W):

• At 220V voltage: 7000W=220V×I, calculated I≈31.82A.
• At 240V voltage: 7000W=240V×I, calculated I≈29.17A.

Therefore, a 7kW charger will typically require about 30-32 amps when operating from a 220-240V single-phase supply. According to electrical safety codes, continuous loads (such as EV charging) should generally not exceed 80% of the circuit breaker rating. Therefore, installing a 7kW charger will typically require connection to a dedicated 40-amp circuit breaker for safety reasons.

How fast does a 7kW EV charger charge?

The 7 kW charging power means that in theory 7 kWh of electricity can be replenished for an electric vehicle battery every hour. This speed is much faster than Level 1 charging and is sufficient to meet the daily charging needs of most electric vehicle users.

We convert the 7 kW power into a more intuitive increase in driving range per hour. Assuming that the average energy consumption of an electric car is 15 kWh per 100 km (that is, each kWh can travel about 6.67 km). Then when charging with a 7 kW charger, the theoretical increase in driving range per hour is approximately:

7 kW * 6.67 km/kWh ≈ 46.7 km/hour

If we calculate based on 0.3 kWh per mile (i.e. about 3.33 miles per kWh):

7 kW * 3.33 miles/kWh ≈ 23.3 miles/hour

This speed means that if you commute 50 kilometers (about 30 miles) every day, and connect your vehicle to a 7kW charger when you get home, it will take only about 1 to 2 hours to fully replenish the power consumed that day. Even if your battery capacity is larger or you drive a lot that day, a 7kW charger can usually charge the battery from a lower level (such as 20%) to a higher level (such as 80% or full) during the 8-10 hours of non-use period at night.

The speed provided by a 7kW charger is a very practical balance for the vast majority of home users. It is much faster than Level 1 charging, can replenish a large amount of power in the vehicle overnight or during working hours, and has lower installation requirements and costs than 11kW or 22kW, and is more compatible.

Why are 7kW chargers so popular?

The 7kW charger has become the mainstream choice in the market because it strikes a good balance between several key factors:

1. Sufficient and practical speed: For most users whose daily mileage is less than 100 kilometers, a 7-kW charger can fully charge the car within a few hours after returning home or overnight, fully meeting the needs of daily commuting and weekend travel, and effectively solving the "range anxiety".
2. Relatively low installation requirements: Unlike 11kW or 22kW chargers, which usually require higher amperage circuit breakers (60A or higher) or even three-phase power, 7kW chargers typically only require a dedicated 40-amp single-phase circuit. This is relatively easy to achieve in the electrical systems of most modern homes without requiring large-scale electrical box upgrades or the introduction of new power lines.
3. Better overall cost: The 7kW charger equipment itself is usually less expensive than higher-powered chargers. What’s more, due to its relatively low electrical infrastructure requirements, installation costs are also usually cheaper than installing an 11kW or 22kW charger.
4. Wide range of vehicle compatibility: The maximum power of the onboard AC charger of many electric vehicles is 7 kW or close to 7 kW (such as 6.6 kW). Even if the onboard charger power of the vehicle is less than 7 kW, the 7 kW charger can be used to charge at the maximum power allowed by the onboard charger. This means that the 7 kW charger can adapt to the vast majority of electric vehicles on the market, and there will be no performance waste of "a big horse pulling a small cart" (relative to the vehicle's onboard charger).
5. Meet the time-of-use electricity price charging: 7 kilowatts of power can quickly replenish a large amount of electricity during the low electricity price period at night. Combined with the intelligent charging function, it can maximize the use of low electricity price periods for charging and save electricity bills.

It is these factors that make the 7kW charger a cost-effective and widely applicable home charging solution.

How to calculate charging time using a 7kW charger?

To calculate how long it takes to fully charge an electric vehicle battery using a 7 kW charger, you can use this basic formula:

Charging time (hours) = required amount of electricity (kWh) / actual charging power (kW)

The "Amount of electricity to be charged" is the amount of electricity you want to charge from the current level to the target level. The "Actual charging power" is the lower value of 7 kW and the maximum power of the vehicle's onboard charger. Assume that your vehicle's onboard charger supports at least 7 kW.

Example calculation:

Assume that your electric car battery has a total capacity of 50 kWh and the onboard charger supports 7 kW AC charging. You plan to charge from the remaining 10% (5 kWh) to 90% (45 kWh). The amount of power you need to charge is 45−5=40 kWh.

Charging time using a 7kW charger:

Charging time = 40 kWh / 7 kW ≈ 5.7 hours

If the battery capacity is 80 kWh, to charge from 20% to 80%, 0.6×80=48 kWh of electricity is required.

Charging time = 48 kWh / 7 kW ≈ 6.86 hours

These calculations show that for common battery sizes, a 7 kW charger could replenish the majority of the charge in a few hours (typically during overnight rest time), ensuring the vehicle has ample range for the next day.

The actual charging time may vary slightly due to factors such as the battery management system's charging strategy (such as reducing the charging speed when nearly full), battery temperature, ambient temperature, grid voltage fluctuations, etc.

Is a 7kW EV charger suitable for me?

Through the above analysis, you can determine whether a 7 kW charger is the ideal choice for you based on your specific situation. Please consider the following questions:

• What is the maximum power of your EV's onboard AC charger? If it supports at least 7 kW, then a 7 kW charger will work at its maximum speed. If it is less than 7 kW, you can consider a charger that better matches the vehicle's power, or still choose 7 kW to prepare for future vehicle upgrades (if your battery box and budget allow).
• How much mileage do you drive each day? If you drive less than 100-150 km per day most of the time and usually have plenty of overnight parking time (8-10 hours), then the speed provided by a 7kW charger is usually completely sufficient.
• What is your home's electrical infrastructure like? Most modern homes can relatively easily install a dedicated 240V circuit at 40A to support a 7kW charger. If your electrical box is older or underpowered, you may want to consult an electrician to assess the feasibility and cost of upgrading.
• What's your budget? A 7kW charger is usually more affordable than an 11kW or 22kW charger in terms of equipment and installation costs.
• How fast do you need charging? If you have extremely high charging speed requirements, or your vehicle supports higher AC charging power (such as 11kW or 22kW), and you are willing to bear the higher equipment and installation costs, then a higher power charger may be a better choice.

For the vast majority of electric vehicle owners, especially those who charge their vehicles at home, have a moderate daily commute, and want to strike a balance between speed, cost, and installation convenience, a 7kW electric vehicle charger is a very wise and practical choice. It provides a speed far exceeding Level 1 charging, enough to fully charge the vehicle during non-use hours, while being relatively friendly to the requirements of the home electrical system and having a more cost-effective approach.

Tips for Buying a 7kW Electric Vehicle Charger

When choosing a 7kW electric vehicle charger, in addition to the core power and compatibility, you can also pay attention to the following practical features:

1. Smart charging function: Many 7kW chargers have Wi-Fi or Bluetooth connectivity and a mobile app. Through the app, you can remotely monitor the charging status, set a scheduled charge (to take advantage of off-peak electricity prices), view charging history, and even perform simple fault diagnosis. Smart functions greatly improve the convenience and cost management of charging.
2. Safety certification: Make sure the charger complies with relevant safety standards and certifications (such as UL, CE, CCC, etc.). These certifications are the basic guarantee of product quality and safety.
3. Durability and protection level: If the charger is installed outdoors, you need to choose a product with a high IP rating (such as IP55 or IP65) to resist rain and dust. The casing material should also be strong and durable.
4. Cable management: Consider whether the charging cable is long enough and whether the charger offers a convenient cable hook or storage design.
5. User interface: An indicator light or small screen on the charger clearly displays the charging status for easy viewing by the user.
6. Brand and after-sales service: Choose a brand with a good reputation to obtain more reliable product quality and more complete after-sales service.

How do I install a 7kW EV charger?

Unlike installing an 11kW or 22kW charger, which may require three-phase power and extensive electrical box modifications, installing a 7kW charger is a relatively simple electrical upgrade for many modern homes. However, it is still an electrical project that requires expertise and must be installed by a qualified professional electrician.

Installation steps and considerations:

1. Check the capacity of your electrical box: First assess the total capacity of your home's electrical box and the current electrical load. Installing a 7kW charger (which requires a 40A breaker) will add a large continuous load. Make sure the electrical box has enough total capacity and at least one available double-pole breaker slot to install a 40A breaker.
2. Install a dedicated circuit breaker: Install a new, double-pole circuit breaker rated at 40A in the electrical box, dedicated to the electric vehicle charger.
3. Run a dedicated circuit: Run a new dedicated cable from the 40A breaker at the electrical box to the charger installation location. The cable must be of a gauge (wire diameter) that can safely carry 30-32 continuous amps and comply with local electrical codes. Typically, 10 AWG (or 6mm²) or larger copper cable is required, depending on the distance and local codes.
4. Choose an installation location: Choose a location that is close to a parking space, convenient for connecting to the vehicle, and easy for wiring. If installed outdoors, make sure the charger has adequate water and dust resistance (IP rating, IP55 or higher is recommended).
5. Physical Installation and Electrical Connections: Securely mount the charger device on a wall or pole and have an electrician make standard electrical connections, including connections to a dedicated circuit and grounding.
6. Comply with regulations and apply for permits: All installation work must strictly comply with local electrical installation regulations. Depending on the region, electrical construction permits may be required and inspections may be required upon completion.

Although the 7 kW installation requirements are lower than for higher power chargers, it is still a high power continuous load device and incorrect installation can cause serious safety issues. Therefore, never install it yourself and always hire a professional electrician.

in conclusion

In summary, the 7kW electric vehicle charger is a very popular and highly recommended home AC charging solution on the market. It works on a standard 220-240V single-phase power supply and usually requires a 40-amp dedicated circuit. For the vast majority of electric vehicle users who want an efficient, reliable, economical and compatible home charging solution, the 7kW charger is undoubtedly the most mainstream and practical choice on the market.