Solar panels, are yours making you greener?

g600dey

I ask this question because my energy supplier keeps asking me to increase my monthly direct debit, even though I've had panels and a battery fitted. I've looked at my energy use and, to me, my use is higher then before. So I checked.

For week commencing 13/01/25 I left my panels switched on, took a meter reading,and lived life as normal(used 56.005 units)

For week commencing 20/01/25 I switched my panels off. took a meter reading, and lived life as normal( used 34.992 units)

I don't think I changed my electric use during the second week, so now I switch the panels off over night and when it is not sunny.

I've also noticed the battery charges up from the grid, if I've left the panels off for a couple of days.

I don't think Solar panels are green, and they cost      a lot.

Keep_pedalling

Your panels won’t be generation a lot of power in January. In my neck of the woods w/c 13th Jan saw very little in the way of sunshine the following week was significantly better and we exported 7x more. 

Your solar panels don’t draw any power while the sun is not shining so that is not the reason for the difference. 

QrizB

You say you've got a storage battery.

Do you have an electricity tariff where energy is cheaper at specific times of day, eg. overnight? Is your battery set to take advantage of this?

I also agree with keep_pedalling that January is not a good time to run an experiment like this.

FlorayG

g600dey said:

I don't think I changed my electric use during the second week, so now I switch the panels off over night and when it is not sunny.

I've also noticed the battery charges up from the grid, if I've left the panels off for a couple of days.

I don't think Solar panels are green, and they cost      a lot.

Why do you switch them off? There's absolutely no reason to do that so I don't understand. If your battery charges from the grid it's because you have it set up to do that. Mine doesn't, it charges only from the panels; yours won't do that obviously if you switch them off and it may be a safety thing to charge from the grid to prevent battery damage from being completely discharged ( I don't know this, just guessing, but even in very cloudy rainy weather there will be SOME trickle charge from the panels to the battery if they are switched on)
As for your supplier constantly asking to increase your DD I get that too; when I ring them they say sorry, our system is not set up to account for solar panels, we will leave it as it is then 

Newbie_John

Solar panels have no impact here.

Battery can have a little impact though, it takes more energy than it gives back - as there is about 10% of loss - also depends where you battery is placed - as I could imagine if it's placed outdoor it would use more energy to keep itself warm.

The difference you showed is tiny, it could be just sheer luck really, one week you did roast and one week you had a takeaway.

Anyway, compare in summer - it's about year average really.

tim_p

In the bleak winter months pretty much all my generation gets used by the house, offsetting what I would otherwise pay for. Two systems, one 4 kWh from 2014 and the other (4.92kWp - 2023/4), manage between them around 500-550kWh over Nov, Dec & Jan. 90+% of that gets used by the house, so that’s a saving straight off the bat. The rest of the year, with battery storage, works out that I use less than 50kWh in total between Mar and Oct. Currently only getting the FIT from the 2014 system (around £900/year) but in process of metered sorting export for both.  Best money I’ve ever spent. 

g600dey

I take on board all you have to say but when my panels are switched off my house uses about 12 watts an hour over night. However when my panels are on the house uses about 80watts an hour. and my predicted use has gone from 1700units a year to 2100units, a big jump. My only change is the solar panels and battery. Okay I'm predicted to generate 3600+ but that's at 15ppunit,grid is 29ppunit.

Another thing I am using less energy on days when the panels are off then when they are on, go figure.

mmmmikey

g600dey said:

I take on board all you have to say but when my panels are switched off my house uses about 12 watts an hour over night. However when my panels are on the house uses about 80watts an hour. and my predicted use has gone from 1700units a year to 2100units, a big jump. My only change is the solar panels and battery. Okay I'm predicted to generate 3600+ but that's at 15ppunit,grid is 29ppunit.

Another thing I am using less energy on days when the panels are off then when they are on, go figure.

Hi - do you have separate inverters for the solar panels and battery system, or is this a hybrid system where they are connected to the same inverter? If the latter, then what is possibly happening is that the inverter is in standby mode overnight so it can spring into action quickly if it needs to so it can power the house using energy from the battery. 68W is still a lot for that, though. How are you measuring this? 

I expect that what is happening is related to the battery system (or battery part of the overall system) rather than the solar system. I had similar issues with a battery system until it was set up correctly. Most solar systems switch themselves off automatically when there's no sunshine so the power draw is minimal.

Qyburn

Just for comparison my Solaredge is supposed to have an idle consumption of 2.5W. However actual measured overnight consumption averages more like 18W. A couple of people on the Solaredge Facebook group have found the same.

Reed_Richards

If you have a battery and can charge it overnight at a cheap rate then you should be doing that.  If you cannot do that then you should set the minimum state of charge to something like 50% at this time of year.  If it's set to 10% (or whatever your allowed minimum is) then after a few dull days (or if you switch your panels off) it will slowly discharge down to a point where your inverter will add some charge from the grid to stop the battery getting to an unhealthy state of discharge.  You've noticed that happening and it's costing you money unnecessarily.  It may also be harming your battery if you switch things off for too long.  

QrizB

g600dey said:

I take on board all you have to say but when my panels are switched off my house uses about 12 watts an hour over night. However when my panels are on the house uses about 80watts an hour. and my predicted use has gone from 1700units a year to 2100units, a big jump. My only change is the solar panels and battery. Okay I'm predicted to generate 3600+ but that's at 15ppunit,grid is 29ppunit.

Another thing I am using less energy on days when the panels are off then when they are on, go figure.

Thinking about this again last night and I had an idea.

Your hybrid inverter is probably using current clamps to sense how much power your home is drawing from the grid. These aren't entirely foolproof and sometimes need a bit of adjusting to make sure they know where zero is. This might be your problem.

Did your installers leave instructions? If not, do you know the make and model of your inverter? Or do you want to contact the installers and ask them to come back to adjust it?