Energy is imported from the grid when there is enough generation (battery never got below 70% yet)

eldaniel · May 23, 2022

I have on grid system with 2 strings going to dual MPPT inverter and 6kW battery. It usually happens when there is no generation but as seen on the photos below it does happen on occasions when solar production is sufficient to cover the load. Sometimes this trickle of import will add up to 1kW a day which is over £100 a year of energy imported unnecessarily. I would really appreciate if someone could explain why is this happening and is there a way to prevent this please?

[ElectriciansForums.net] Energy is imported from the grid when there is enough generation (battery never got below 70% yet)

littlespark · May 24, 2022

What does your supplier say about it?

Is there a time during the day that consumption is over generation? Even for just a few minutes… Electric shower for example?

eldaniel · May 24, 2022

littlespark said:
What does your supplier say about it?

Is there a time during the day that consumption is over generation? Even for just a few minutes… Electric shower for example?

Only once I noticed that I used 4.8kW when the sun was down but then it took correctly 3kW from battery and 1.8kW from the grid as battery maximum output is 3kW. During the day if consumption is high like solar + battery cover it nicely. As you can see this trickle import happens very often when load consumption is very little. I have not spoken with my installer about that yet as I am in a process of sorting about the other problem. Panels were not correctly installed (hooks sit on a slate etc) so I did not ask them yet as I thought I will explore with them one problem at a time.

r8sso80 · Jun 14, 2022

eldaniel said:
I have on grid system with 2 strings going to dual MPPT inverter and 6kW battery. It usually happens when there is no generation but as seen on the photos below it does happen on occasions when solar production is sufficient to cover the load. Sometimes this trickle of import will add up to 1kW a day which is over £100 a year of energy imported unnecessarily. I would really appreciate if someone could explain why is this happening and is there a way to prevent this please?

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Did you find out why this was happening? I have a similar situation where grid energy is being used when really I wouldn't expect it to.
It's not just your example, there are times where I'm producing PV and there's enough to meet consumption but the app shows me charging the battery, covering most of the consumption but still drawing from the grid... quite frustrating as like you say, these trickle feeds add up over time and cost money.

eldaniel · Jun 14, 2022

r8sso80 said:
Did you find out why this was happening? I have a similar situation where grid energy is being used when really I wouldn't expect it to.
It's not just your example, there are times where I'm producing PV and there's enough to meet consumption but the app shows me charging the battery, covering most of the consumption but still drawing from the grid... quite frustrating as like you say, these trickle feeds add up over time and cost money.

eldaniel · Jun 14, 2022

Unfortunately I could not find the definitive answer. Some people say it will always be like that because inverter will never switch perfectly between import and battery. I have checked over many days and mostly occuring when when solars not generating and the biggest draw is usually as the sun is rising and solars about to start producing and the same at the end of the day. I will have the company rep to do some remedy action on the install soon so I will ask him that question and let you know if I will get anywhere. However it is frustrating because you are paying for something you don't have to...