Understanding Import Limit Feature
The Import Limit feature allows you to specify the maximum power which your battery can charge from the grid. This is your primary tool for capping the charging load and helping to prevent high-demand charges.
Why Is an Import Limit Important?
An import limit serves two main purposes.
1. Protecting Your Electrical System
- Every electrical system has physical limits defined by its wiring and fuses. Exceeding those limits can trip fuses, cause outages, or damage components.
- By setting an import limit, you ensure that total grid consumption stays within safe boundaries, reducing the risk of failures and electrical hazards.
2. Avoiding High Energy Costs
- In some countries (for example, Sweden), electricity pricing is partly based on monthly peak power usage, not just total energy consumed.
- If you charge your EV while also charging your home battery, your grid demand can spike sharply. Even a few short peaks within a month can push you into a higher pricing tier, increasing your electricity bill unnecessarily. An import limit helps smooth these peaks and keeps costs under control.
How Import Limit Works
When an import limit is set, the system ensures that total power drawn from the grid never exceeds that value.
Examples (with a 7000W limit):
- Zero home consumption: Battery charges at the full 7000W power.
- Home consumption (e.g., oven) is 1500W: Battery charge is automatically reduced to 5500W (7000W - 1500W).
- High home consumption (e.g., 8500W): Battery charge is reduced to 0W, so consumption will be fully covered from the grid
Setting the Right Import Limit
When choosing an import limit, you should consider both your grid contract and your main electrical fuse. In practice, the safest limit is usually below the theoretical maximum.
1. Grid Contract Limit
Your grid contract may specify a maximum allowed import and export power (for example, 15 kW).
Even if the contract allows 15 kW, it is recommended to set the import limit slightly lower, typically around 13–14 kW.
Why?
Because household loads can change very rapidly. In some situations, the inverter or energy storage system may not react instantly, causing short power spikes that temporarily exceed the limit. A small safety margin helps avoid contract violations and unnecessary issues.
2. Main Fuse Limit
The second constraint is your main electrical fuse.
For example, with a three-phase 25 A main fuse, the theoretical maximum power is based on nominal grid voltage. However, this assumes perfectly stable voltage, which is rarely the case in real-world conditions.
The acceptable voltage range is typically ± 5%, meaning voltage can vary roughly between:
- 220 V and 240 V for residential sites
- 380 V and 420 V for C&I sites
Instead of a fixed 230 or 400 V.
As a result, it is generally best to use the lower end of the range as a conservative and reliable setting.
Single-phase systems
For single-phase connections, voltage is often closer to 220 V rather than 230 V. With a 25 A fuse, this means the recommended maximum import limit is around 5.5 kW.
Larger (C&I) systems
In commercial and industrial setups, the same principle applies.
For example, with a three-phase 250 A connection, voltage variation between 380–420 V results in a practical power range of roughly 164–181 kW.
In real deployments, limits are often set conservatively (for example 165–170 kW) based on observed voltage behavior under load, charging, discharging, and solar production.
Practical recommendation
If you are unsure about your exact grid behavior:
- Start with a conservative (lower) limit
- Observe system behavior
- Adjust if needed
In some cases, a simple trial-and-adjust approach is used. If protection devices trip or issues occur, the limit should be reduced.
Where to Set Import Limit
Import Limit can be set in the Settings tab under the Import Limit section.
If you do not see it available under the Settings tab, it is not yet supported for your inverter vendor.
When Import Limit Applies
Import limits mainly apply when the system actively controls battery charging or other flexible loads.
If essential household consumption alone exceeds the configured import limit, the system will still allow the required power from the grid. Home safety and continuity are always prioritized over optional loads such as battery charging.