With the popularity of electric vehicles, home charging piles have become an essential infrastructure for car owners. However, faced with the two mainstream charging power options of 7kW and 22kW on the market, consumers often fall into a dilemma of choice - whether to pursue a low-cost, easy-to-install 7kW charger, or invest in a higher-power 22kW device? This article will conduct a comprehensive analysis from the dimensions of technical parameters, economic costs, and applicable scenarios to help you make a wise decision.
I. Analysis of Basic Concepts
1. Power Definition
A 7kW charger can charge 7 kWh per hour, which is equivalent to the standard charging speed under a single-phase power supply (220-240V). It is suitable for daily home use and can usually complete vehicle energy replenishment at night. A 22kW charger charges 22 kWh per hour and requires support from a three-phase power supply (380-415V). Its charging speed is more than three times that of a 7kW charger, but it requires dual support from the power grid and the vehicle.
2. Differences in power types
Single-phase power (7kW): Standard configuration for most households around the world, it can be installed directly using existing circuits without additional modification. Three-phase power (22kW): Commonly found in industrial or commercial buildings, home users need to apply to the power company for upgrading the power grid if they need to install it, which is costly and time-consuming. Methods for determining power type: Single-phase power: There is only one main fuse or circuit breaker in the power box. Three-phase power: There are three independent main circuit breakers in the power box, usually marked as "L1/L2/L3".
II. Technical parameter comparison
1. Charging speed
Although the theoretical speed of 22kW is three times that of 7kW, the actual charging efficiency is limited by three factors:
Vehicle charging limit: The on-board charger (OBC) of most models only supports 11kW or lower power.
Battery management system (BMS): The vehicle will dynamically adjust the charging power according to the battery temperature and remaining power, especially significantly reducing the speed after the power exceeds 80%.
Comparison of charging time for typical models ( 0-100% )
| Model | 7kW charging time | 22kW charging time |
| Tesla Model Y | 10 hours | 6 hours 43 minutes * |
| Nissan Leaf ( 40kWh ) | 7 hours | 7 hours |
| Porsche Taycan | 9 hours and 30 minutes | 4 hours |
Note: The vehicle must support three-phase 11kW charging, otherwise the speed is the same as 7kW .
Output power of charging piles: The output power of all charging piles is specified. If you choose a charging pile with an output lower than 22kw, you will not be able to achieve a 22kw power output.
2. Installation requirements
The output power of the 7kW charger is small, and the requirements for the circuit are low, so the installation cost is also lower. The 7kW charger only needs to use a circuit compatible with a single-phase household power supply. The installation cost is about 300-800 pounds (including labor), and some areas can also apply for government subsidies. The 22kW charger has high requirements for the circuit, and the household power grid needs to be upgraded to a three-phase power supply, which may cost more than 2,000 pounds. The charger cable must also use a 3-core 6mm² or above Type 2 cable.
III. Applicable scenario analysis
1. Home users
Recommended 7kW scenario:
- Daily mileage is less than 100 kilometers (such as commuting, short trips).
- Mainly charging at night, no need for fast energy replenishment.
- The budget is limited or the power grid cannot be upgraded to three-phase electricity.
Consider the special situation of 22kW:
- The family has multiple electric vehicles and needs to shorten the queuing time for charging.
- The vehicle supports high-power charging (such as Porsche Taycan, Audi e-tron GT).
- Three-phase electricity has been pre-installed or is planned for long-term use (such as future high-performance models).
2. Commercial/public places
The core advantages of 22kW:
- Improve user stay experience: shopping malls, office areas and other places can attract customers with fast charging.
- High turnover rate: shorten the charging time of each vehicle and maximize equipment utilization.
- Parking lots can be equipped with 7kW (low-cost coverage) and 22kW (high-end demand) equipment. For example: 80% of parking spaces are equipped with 7kW, and 20% of parking spaces are equipped with 22kW, balancing efficiency and cost.
IV. Economic considerations
1. Initial cost
Equipment price:
- 7kW: entry-level model is about 359 pounds (such as Zappi V2), and high-end model (including solar optimization) is about 859 pounds.
- 22kW: The price is usually 30%-50% higher, about 1000-1500 pounds.
Circuit transformation:
The cost of upgrading a household to three-phase electricity varies from place to place. The average cost in the UK is £1,500-2,500, and additional approval from the grid company is required (2-8 weeks).
2. Long-term returns
Household scenario:
The average annual electricity bill of 7kW is about £200-400 (compared to public fast charging), and the payback period is about 3-5 years. 22kW is only meaningful for a few households, such as two long-range electric vehicles that need to be fully charged every day.
Commercial scenario:
Assuming an hourly charge of £0.5, the 22kW charging pile is used for an average of 6 hours a day, with an annual income of about £1,095 and a payback period of about 5-7 years.
V. Compatibility and limitations
1. Vehicle adaptability
Check the specifications of the on-board charger: Some models (such as Mitsubishi Outlander PHEV) only support 3.7kW charging. The 22kW charger only runs at 7kW in a single-phase circuit and cannot reach full speed.
2. Cable versatility
Advantages of 22kW cable: supports three-phase current and can be adapted to higher-power public charging piles in the future. Reverse compatibility risk: 7kW cable used for 22kW equipment may cause overheating or damage.
VI. Key decision factors
1. Necessity assessment
Daily mileage: 7kW for 100 kilometers; 22kW for 150 kilometers and the vehicle supports high power. Grid conditions: Three-phase electricity is a hard threshold, and it is necessary to contact the power company first to confirm the feasibility.
2. Future scalability
Choose a charger that supports dynamic load management (such as myenergi Zappi), which can integrate solar energy or energy storage systems. Reserve upgrade space: Ensure that the capacity of the power box can support future capacity expansion needs.
VII. Frequently Asked Questions
Q1: Can a 22kW charger be installed in a single-phase home?
A: It can be installed, but the charging power is limited to 7kW unless it is upgraded to three-phase electricity.
Q2: Will 22kW charging damage the battery?
A: No. The vehicle BMS system will actively limit the current to ensure battery safety.
Q3: What is the government subsidy policy?
A: The UK OLEV subsidy is 75% of the installation fee (upper limit of £350), which only applies to 7kW devices.
VIII. Conclusion and Recommendations
- Home users prefer 7kW: taking into account cost and efficiency, and adapting to the existing power grid.
- Commercial/multi-car households choose 22kW: long-term demand and feasibility of power grid transformation need to be strictly evaluated.
- Ultimate principle: Based on vehicle performance, electricity usage habits and infrastructure decisions, professional electricians should be consulted for on-site evaluation.
From the above analysis, it can be seen that the choice of 7kW and 22kW chargers is not simply "the higher the power, the better", but requires comprehensive consideration of multiple factors such as technology, economy, and usage scenarios. In today's rapid iteration of electric vehicle technology, rational investment can maximize the long-term value of charging equipment.
