Why doesn’t my solar or battery app match my meter readings?
This is normal. We expect there to be a difference between the two. However It shouldn’t be too large - a 5-10% difference is pretty common.
The meter records every kWh that is imported from the grid to the property or exported to the grid. Your app shows you what is happening on the house side of the meter and is usually measured at several different points.
So, what about where there’s a huge difference?
Firstly, your electricity meter is almost certainly correct. It is a “revenue grade” tool that is extremely accurate at measuring the energy that flows through its import and export channels. Meters are certified and thoroughly tested so it’s a very rare occurrence that we see one that is recording incorrectly.
We have occasionally seen the channels set up in reverse - so the export thinks it’s import or vice versa, or the meter just stops sending data. However these issues are obvious and easy for us to spot.
Your solar app will generally take data from the inverter and from CT (current transformer) clamps that are clipped around the cable to measure current. If the clamp(s) are in the wrong place, that will lead to wrong data. They also come in varying qualities (and costs) and generally speaking a lesser quality CT clamp will have a larger margin of error.
A lot of solar apps also do a few calculations, rather than presenting straight import/export/usage data - sometimes these values are labeled with names that are easy to misinterpret. Sometimes the numbers the app presents don’t seem to add up logically either so it becomes even harder to align this with what the meter is saying.
If you have a multi-phase supply, that has a few more complexities. We’ve seen situations where people have found themselves importing from the grid on one phase while simultaneously exporting on another. Multi-phase solar should ideally have a load-balancing inverter to manage this. If you have a multi-phase supply, make sure you discuss the implications of this with your solar installer.
What should I do if there is a big difference?
We advise you to talk to your solar installer in the first instance. They understand how your system works and how the measurement devices are set up.
Your installer will also be very familiar with your app and what it means. Get them to explain the measurements your app displays to make sure you are comparing apples with apples.
Download your half-hour data from the Octopus Energy website for the time period you are concerned about. Share the data with your solar installer so they can look into the differences between the inverter and the meter data. Following their analysis either they will make some changes or you can come back to us to investigate it further.
If your solar installer cannot shed any light on the difference, the last resort would be a meter accuracy test. We say to do this last because, if the meter is found to be accurate, the fee is $260, and as we mentioned earlier, they are almost always accurate.
