In the process of preparing for the construction of a commercial ev charging stations, the first and core question that many friends encounter is: “How big of a transformer should I have?” This question is crucial because box transformers are like the “heart” of the entire charging pile, converting high-voltage electricity into low-voltage electricity available to electric car charging piles, and its selection is directly related to the operational efficiency, initial cost and future scalability of the ev charging station.
1. Basic principle: power matching is the core
The first step in selecting a transformer is to perform an accurate power match. The basic logic is very simple:
Calculate the total electric vehicle charging station power: Add up the power of all the charging stations you plan to install.
Matching transformer capacity: The capacity of the transformer (unit: kVA) should be slightly greater than the total power of the ev charging station (unit: kW) to leave a certain margin and buffer space for the system.
2. Practical cases: calculation methods that can be understood at a glance
Let’s use two typical cases to calculate for you:
Case 1: Build 5 120kW DC fast charging piles
Total power calculation: 5 units × 120kW/unit = 600kW
Transformer selection: At this time, choosing a 630kVA box transformer is the most suitable and common choice. It can perfectly carry a total load of 600kW while leaving a reasonable margin to ensure stable and efficient operation of the equipment.
Case 2: Build 10 120kW DC fast charging piles
Total power calculation: 10 units × 120kW/unit = 1200kW
Transformer Selection: For a total power of 1200kW, your best choice is a 1250kVA box transformer. This specification is tailored for this power level, ensuring sufficient and reliable power supply.
Through the above examples, you will find that the selection of transformers is not just imagined, but has a clear mathematical logic to follow.
3. Advanced thinking: reserve space for future development
Having forward-looking planning at the beginning of the project is a sign of business acumen. If you foresee the possibility of future expansion of the electric car charging station, you should consider giving it a stronger “power” when choosing the “heart” in the first step.
Advanced strategy: Upgrade transformer capacity by one notch as budget allows.
For the case of 5 piles, if you are not satisfied with 630kVA, you can consider upgrading to an 800kVA transformer.
For a 10-pile case, a more powerful 1600kVA transformer can be considered.
The benefits of this are obvious: when you need to increase the number of electric car charging piles in the future, there is no need to replace the transformer, which is the core and expensive equipment, and only relatively simple line expansion is required, which greatly saves the cost and time of secondary investment, allowing your ev car charging station to have strong growth.
In conclusion, choosing the right transformer for a ev charger is a decision-making process that balances “current needs” with “future development”. Accurate capacity calculations are fundamental to ensuring the stability of current operations, while moderate forward-looking planning is a critical insurance for continued ROI growth.
If you are planning a charging station project and still have questions about transformer selection, please feel free to contact us. We are willing to use our professional technical experience to provide you with free customized solution consultation to help you build an efficient charging station with growth potential!
EV charging station customized manufacturer, CHINA BEIHAI POWER CO.,LTD.
Post time: Nov-05-2025
