What should the PV produce on a cloudy day?

[Northspoon]

I have only had the system a few months but I am disappointed with the PV output on a cloudy day. Should I expect it to be better?

I have 12 Aiko panels (445 W each) with Tigo optimisers on two strings going to a Foxess Hi-5.0-E.G2 inverter and batteries. These PV panels are on a south facing garage roof at a pitch of 36 degrees. The roof area is not shaded after 9am.

Today is cloudy and the time is 1pm but the output is only 224W (4.6%). Any advice appreciated.

[Dave Foster]

This is my total PV today, it's been a mix of cloudy, sunny and very cloudy.

My system has 16 * 400 W panels but face a mix of directions East, South & West and quite a few moments today they were doing ~310 watts

224W is low but a lot depends on the suns elevation and how dense the cloud cover was - My lowest output for an *entire* winters day was 0.43kWh

It's best to look at your trace for the day to see how it is performing across the whole day, can you post that.

[Northspoon]

Silly question.....but how do you get that graph? Is it through the Fox ESS Cloud app? My app only seems to show a different graph.

[Dave Foster]

I was using home assistant, but you can get a similar graph on the Fox cloud website by scrolling to the bottom of the inverter details page you posted and in the drop down menu in the empty graph, choose PV Power and press search

[Northspoon]

Thank you Dave, I didn't know that existed it was so greyed out. Here is todays graph. It looks a bit better than I first thought.

[Dave Foster]

Thank you Dave, I didn't know that existed it was so greyed out. Here is todays graph. It looks a bit better than I first thought.

How does that compare with yesterday ? (i’m assuming it was as sunny where you are located as it was in the North West)

Update, it’s gone so cloudy now i’m down to 122 watts

[Northspoon]

I am in the South East where it has been overcast for several days.

I really don't know what to expect from a potential 5kW array on a dull day this time of year. I am on an Economy 7 tariff and so far, since the installation in May this year, I have only used the grid on the cheaper rate, using the battery and solar during the day rate period.

[reef]

We did 7.6kWh today with 9.42kW of panels.

Trust me it gets worse. We did 0.08kW on 2nd January this year (admittedly with only 4.8kW of panels back then, but still!). We had a peak of about 50 watts that day!

I've managed 55.2kWh on a good day in May but only 88kWh all month last December.

The dark months can be dire!

[Northspoon]

Thank you, I guess I was expecting too much of our PV system. On a good sunny day in July we were getting close to 5kWh at mid-day.

[calum]

Thick low cloud will really hurt solar output; overcast-yet-bright days can be surprisingly good. Over time you get a feel for it, weirdly.