Wait… Why Am I Still Importing Power?

3 min read.

Why Am I Still Seeing Grid Imports After Installing a Battery?

Congratulations on installing a home battery. Many new battery owners assume that once a battery is on site, especially a large one, the electricity bill should drop to zero.

So it can come as a surprise when the next bill arrives and there are still small grid imports showing up.

This is actually completely normal. Even a perfectly good working solar and battery system will still import a small amount of energy from the grid. Here are main reasons why this occurs and why it is normal.

Response Time (The Biggest Factor)

Appliances demand power instantly. Batteries do not move quite as fast.

When you switch on an appliance such as a kettle, the home suddenly needs around 2000 watts of power. At that moment the home pulls that energy from the grid. The solar and battery system notices the load and starts to respond, but it takes a few seconds to safely ramp up and take over.

Lithium batteries cannot instantly jump from charging to discharging or even from one discharge level to another. They need to transition smoothly for safety, battery life and reliability. Inverters also follow ramp rate rules, which limit how fast they are allowed to change output. These rules support grid stability and prevent sudden power spikes.

During those few seconds of adjustment the electricity billing meter records a small amount of import. Each event is tiny, but during a day or a billing cycle they naturally accumulate.

The same thing happens when the appliance turns off. The load drops instantly, but the battery needs a short moment to ramp down. While it adjusts any extra power briefly exports to the grid. Measurement accuracy and how “zero” works in the real world

Your solar and battery system relies on an internal energy meter to decide when to charge, discharge or export. This is the meter your monitoring apps and dashboards use. It is accurate enough for control purposes, but it is not the same as the electricity company’s revenue meter.

The revenue meter is used for billing and is built to a stricter level of precision. It also costs significantly more across its lifetime, which makes sense because it is used for financial settlement. As a result, it measures energy flows differently.

This is Where Expectations Can Drift! Even when a system is working well, there is no such thing as a perfect mathematical zero at the grid connection point. Your solar and battery system is effectively chasing its own version of zero, while the revenue meter is chasing a stricter version of zero. The two will never match perfectly.

The industry considers anything within roughly 200 watts of the revenue meter to be accurate for residential systems. That number is written into the testing and compliance standards that all systems must pass before being allowed to connect to the grid. To put that into context, 200 watts is an error of about 1.5% for a standard household service. For consumer electronics, that level of accuracy is very high.

This is why it is normal for your monitoring to show zero import while the electricity bill still shows a small amount of energy consumed. Both devices are working correctly. They are simply designed for different jobs. What this means for your electricity bill?

Small amounts of grid import are normal and expected. Even a large battery will not eliminate every watt of import. The idea of zero import sounds simple, but in practice it is not realistic because of response time, ramp rate rules, battery chemistry limits and the difference between control and revenue metering.

If you converted the 200 watt tolerance into energy over a full day, it equals around 4.8 kilowatt hours. That number represents a worst case scenario where the system sits at the edge of its allowed accuracy for an entire day. Most homes do not operate anywhere near this level. Once the system settles in, the real numbers are usually much lower. Does this mean something is wrong

Usually not. Small imports do not mean the battery is faulty, undersized or incorrectly installed. They also do not mean the system is not achieving its goals. Batteries are designed to reduce your electricity bill and increase your solar self consumption. They are not designed to completely disconnect you from the grid for billing purposes. If your imports are significantly higher than expected and your battery is large enough to cover your household loads, then it may be worth having the system reviewed.

The bottom line

Batteries reduce bills and reduce reliance on the grid. They also make homes more resilient and flexible. However, they do not eliminate grid imports entirely. A small amount of import is simply how batteries work when they operate safely within the rules of the energy system. The good news is that most systems perform well below the worst case numbers and the savings accumulate over time.