Why is my Solis solar inverter drawing energy from the grid?

Hi @fabiodifa , the meter readings from your provider (smart meter?) will be more accurate. The clamp monitor is a general guide but not as accurate. These type of systems also tends to give an update every few minutes so can give false readings every so often. 
There are a couple of things to consider. 
The settings on your inverter which might look at a charge state overnight and

Switching routines which at low input levels from the solar and battery system can cause grid demand as they don’t switch as fast as the demand changes 

First of all, thanks for your reply. It seems like an "offset" related to low power consumption, so I think I can't solve it!

You may be correct @fabiodifa. Your monitoring system and inverter will be taking its feed from the clamp so anything you can do to correct that would help overall. I know that several providers have updated their systems over the last few months so just ensure that you have the latest version (I’m sure you do) and the position of the clamp might be significant as well

I have similar situation with my Sunsynk system the grid seems to supply up to about 20% of my power use rather than draw from full batteries, whatever the load requirement is, But not all the time! Usually runs at about .05 Wfrom grid. 
I also notice that the energy supplied by solar panels , battery or grid seems to add up to about 20% more than the power required! Is this normal? 

Hi @Coypu , most systems do have a need to still draw from the grid. Sometimes it depends on how the system has been set up. There will also be times when the solar production will drop due to clouds or suchlike and it can take a while for the battery to switch in. 
Inverters have their own system monitoring to detect and measure power flow but they are not as accurate and so can give differences in value. 
You might be able to adjust a few things if you thought it useful .. but it needs care when changing settings

Dear colleagues,

our SOLIS hybrid inverter draws a small amount of energy (30W) from the grid when it is charging the battery (at say 1.5 kW) and the house consumes say 500W. This small amount of grid energy is registered by our utility meter, so we have to pay for it, even though there is 1500W going into the battery at the same time :-( We would be happier, it would charge 30W less and draw zero from grid.

As long as we had no battery, we could set “maximum exported energy” (600W) and did consume no energy from the grid. Now we still draw a small amount, even though there is enough coming from the panels.

Any ideas?

It’s all about the inverter settings @marsalek. There’s two considerations:

1. The switch between enough solar to charge and supply the house is often slower than you might think and because it’s all designed to give you what power you need when you need it, there can be instances when you draw from the grid as well (even with a charged battery).
2. The inverter monitors what is being drawn by the house (either via a CT or an internal monitor). This can be slightly off calculation and so not be measuring accurately. 

If via CT, there can be a programmed offset put into the calculations to better match need. 
If just switching time is slow, there’s not a lot you can do. 

You are right, the speed of regulation makes it impossible to accurately track sub-second load and PV-supply variations. I’d try to tweak the settings so that we supply a negligible amount into the grid. Where do I find the offset-settings for the CT meter? I am using Eastron SDM630mct. Thank you!

The offset is normally applied via the inverter settings. I don’t have a Solis so not sure if/where they sit. 
Mine (a LuxPower) has a field on the maintenance page 

I found this article on the Solis support site ..

Although yours is a different type, the page might be of use