New Solar Panels installed and confused on usage from Grid

pad406

Hi all

I recently (last week) had a new system installed. 17 panels, 7.2kWp, 2 batteries 10.2kWh, solis inverter and an EDDI for the hot water. After a bit of tweaking I now have my battery charging at night on the cheap rate, and only starting to discharge at 8:00am when the normal day rate kicks in.

Typically the house uses about 14kWh per day on average, based on nearly a years smart meter data, so happy enough that it is an accurate figure, but I have this issue in getting my figures to add up.

For example, last Sunday was a lovely sunny day. I can see from my usage that the battery was fully charged between 2am and 5am that morning. From 8am till 8pm I used 1.6kWh from the grid according to the smart meter. Between 8pm and 2am on Monday, a further 2.3kWh from grid.

According to the Solis cloud site, the panels generated 24kWh and exported 3.78, so a nett 20kWh must have been used in the house?

But at 2Am the next day I can clearly see the battery having to be fully charged again.

To me, that means the house used 20 (solar) + 8ish (from battery) + 4 (grid), so 32 in total. The Eddi reports 3.5kWh used that day.

Where's all my electricity gone? I would have expected the battery to have been fully charged (at least), yet it wasn't.

I must be missing something I guess.

graememk

If your battery is full in the morning, and it's a good day, it doesn't really get to be discharged until evening/nighttime.

So it goes to the eddi or exported.

The eddi is seen as house usage by the inverter.

pad406

https://www.boards.ie/discussion/comment/121289701#Comment_121289701

That's what I expected, yet the battery, based on the charging the following night, must have been almost completely discharged. so the nett 20 from the solar, 4 imported less 3.5 from the eddi would still leave me with 20ish kWh used even without the battery. With the batter needing to be charged I reckon at least 8 of that was used, so 28 used in total for the day. That's nearly double my normal daily usage. We barely used that on Christmas Day when the ovens, hob were on constantly for 6/7 hours.

graememk

Time to see some of the graphs.

your 10kwh battery is likely only 8 useable, and what was it actually at when it was 2am?

What is your background load?

Gonna keep round numbers for easy counting?

Solar, 24kwh, eddi 4, export 4 = 16kwh used directly or put into the battery.

Battery id say started at 8am but possibly sat fullish until the evening hit. Some import in the 12-2am slot, some import in the 5-8am slot.

Also the solis does tend to run on a slight import when on batteries, That would likely show up on the smart meter in the evening time.

Are you signed up for the ESB Networks login for the smart meter data?

slave1

Just so you know, that battery is likely ~16kWh usable as most batteries won't discharge above 80% use

pad406

Above is the usage as downloaded from the smart meter data in my Electricireland account.

On 22/10 you can see that the battery is charging from 2AM - 5AM, 10kW less normal usage at night of about 1.6, would say about 8.4kW went into the battery. To stop it discharging until 8AM, the charge schedule is 2AM-8AM. 8AM-8PM very little usage from the grid, 1.6 in total. From 9PM to 2am on 23/10 back to normal typical pre-solar usage from the grid, which implies to me that the battery was not being used.

2AM-5AM on the 23rd, clearly battery is being charged. 10kWh again less the normal 1.6ish, therefore 8.4 into battery?

So if from 8AM to 8PM I imported 1.6, generated a nett 20 (24 - 3.78 exported) and the battery was somehow drained of 8kW that means (I think) that almost 30kWH used in the house.

Based on our historical usage that's double what it would normally be.

This would be the last Sun-Wed pre panel installation

graememk

https://www.boards.ie/discussion/comment/121290435#Comment_121290435

What does solis cloud say your use is?

bullit_dodger

Couple of thoughts.

If you are on Day/Night tariff, be aware that in summer the night rate is from 00:00 to 09:00 and in winter it's from 23:00 -> 08:00. It's 9hrs in duration all year round, but it's based off a fixed UTC timezone, hence why it changes in summer as Ireland adopts IST (Irish Summer time). I bring this up as you mentioned......"and only starting to discharge at 8:00am when the normal day rate kicks in." So you were effectively discharging the battery when you could be taking it at night rate from the grid. Roundtripping via the battery will lose 10-15% or thereabouts. Course this weekend as we move to Winter time, your fine as of Sunday discharging at 8am.

Can you post your battery SOC (State of charge) over a few days where you have the problem? E,g here is mine from yesterday

It's a good way in knowing (for us) when and how the battery usage during the day is.

graememk

https://www.boards.ie/discussion/comment/121290779#Comment_121290779

Smart meter tariff, is always 11pm-8am, observing DST (also, IST, Is ireland Standard time, and we actually go -1 for wintertime!, Jonathan told me about that recently!)

https://www.boards.ie/discussion/comment/121290435#Comment_121290435

Also to add, the SM data is pretty meaningless now to see your consumption, as its generally covered by battery, Possibly split it up into Day/Night/EV rates?

(id also recommend signing up for the ESB Networks, and have direct data for the smart meter, Also gives separate readings for export and import)

pad406

So 98% at 16:37, 25% at 20:57. 8kWh used in a little over 4hrs!!!!

Looking at the Eddi it was getting fed between 16:30 and 20:00, so that's where some of my battery went.

But, if the entire day was 3.5kWh, that must only account for 1sh.

And consumption from Solis cloud

And now, FINALLY, it dawns on me.

Darn leaf vacuum/shredder. 3kWh !!!! Spent the nice sunny afternoon vacuuming/shredding leaves, at least it was solar powered :)

Problem solved!

Need to dig around that Solis cloud more, lot of useful info there.

pad406

https://www.boards.ie/discussion/comment/121290800#Comment_121290800

I have signed up to ESB networks, but the figures I've got from that don't match anything else I'm seeing.

Scoobydoobydoo101

Try dividing the read value by 2. They report in 30min intervals

graememk

https://www.boards.ie/discussion/comment/121291129#Comment_121291129

The HDF values are in kW, but over 30 minutes

Divide by 2 to get the kWh.

Also the 5am slot is from 4.31am-5:00am

kevin101

Currently on the Flogas bwg deal. Have the new Rm108 meter fitted so

now being paid for export. What times are current night rates. Smart meter not activated. Thanks

graememk

Night rate hasn't changed from traditional DN it should be 23:00-08:00 now that we are in winter