Now that the lights are on pretty much of all the time (what? 4 months now?) there is no escaping the fact that my Goodwe is nearly always drawing a small amount of power from the grid. Sometimes as low as 3W, more often around 20W, even when there is PV coming in.
It occurs to me (but that doesn’t make it true) that this is deliberate, it is to keep the municipal meter happy. Though there will be a couple of moments in a day when it does try to send a tiny amount back.
The things that one finds to be concerned about now that we are not predominantly concerned with keeping the lights on.
The inverter has a bunch of controllers running inside it. Imagine that it is a little computer. Computers draw power, and so does the little computer inside your inverter. Without that computer, it wouldn’t be an all-in-one device that can do all the things it does.
I’m aware that there has to be some self-consumption, but right now, for EG, there is plenty of solar power coming in, more than enough to run the inverter, run all the loads on the property and charge the batteries.
So what I’m wondering is why is it still drawing 48W from the grid? Not a large amount, granted, but I’m wondering if this is a deliberate strategy or, as @TheTerribleTriplet suggests, just unavoidable because the inverter can’t control everything to the last watt.
Your inverter is probably set to push back 0w to the grid. So it is unavoidable with this setting. The MPPT in the Goodwe lags a little behind the real time demand on your essentials side.
What you might consider, is setting the push back to the grid to 100w. Then you will find, when there is more solar available than your house load + battery charging demand, that the inverter will push a small about back to the grid instead of consuming a small amount. If you have one of the newer prepaid meters, this will be ok, it will block the pushing to the grid and won’t trip, but it will trip if you do more than this. If you have an older prepaid meter, it wont block and also charge you whatever you push back.
It is a choice you make which side you want to be on. I can tell you this, the mppt on my goodwe seems to be more effective and efficient with this setting on 100w than on 0w.
From an engineering view, measuring nothing is a lot harder than measuring something. To keep at 50W is a lot easier than to keep to 0W, because at 0W there is very little to work with.
You will also note that your power factor is absolutely atrocious the lower you go. Inverters typically run close to unity, which means all the good power factor is cancelled out by your RE system, and all the bad power factor is passed on to the grid. I’ve had installers tell me that they don’t understand how they see 2 amps on a clamp meter when the rest of the system reports under 100W. Well, this is why…
Please just accept that a small draw from the grid is a good thing. That is my opinion
On the Sunsynk there is a setting to set the grid draw to 20W mininum (that is changeable, but 20W is the default). The explanation is that some of the prepaid meters (or other meters?) block export and they might trip by mistake if you are too close to 0. So drawing a little is a way to make sure the prepaid meters do not trip by mistake.
It may be called “Zero Export Power” on the device itself. Should be on the System Mode screen. Not home now so can’t snap a pic now. EDIT: Found it in their manual.
This sounds scary. I have the latest and greatest meter that COJ are installing, but when a meter “trips” do we mean that the interface box that displays totals and which you use to enter tokens stops working, or do we mean that you lose grid completely and have to call the City?
Well according to SEMs, my system was feeding back for about an hour and 20 minutes this afternoon. A small amount, never more than about 20W. So clearly my meter can take those small amounts.
In the other place there was recently a post about meters and SEG registration. This included a nice official document. It turned out that “SA” in this document stood for “South Australia” but it was still interesting to me.
By default, in South Australia, all meters act as you describe “wont block and also charge you whatever you push back.” This default behaviour can be overriden if you register the system with the utility and sign up for a specific tariff.
I am betting that they do this so that people don’t try to “rewind” their meter.
I mean, it disconnect your grid to prevent you from exporting to the grid. Then after a while you should get reconnectsd. All theory because I haven’t been disconnected by mine. It is a new one that was installed by coct before I was allowed to install solar
The Enlight Sienna meters that CoCT installs will never disconnect due to reverse power flow. That’s what the installer claimed and I tested and confirmed it in his presence. It simply charges you both ways.
Are these pre-paid meters?
And I understand these aren’t the meters that are used when you apply for feed in to the grid…
So why do they install these meters??
Correct. If you apply to install SSEG and you do not want to feed in they replace your existing meter with this one. You do not have a choice in the matter.
In order to prevent nuisance trips when your inverter momentarily feeds in, and at the same time to discourage you from feeding in.
I suppose they could have allowed you to feed in without charging you, but then they would not know who feeds in and who does not. As I understand it they need to know this when they do planning for maintenance and upgrades to their distribution network.
I have one of those. I can confirm, it does not care if you feed in. It simply bills you for it.
If you apply to feed in, they need to credit you for the amount fed in. They pay you less for that direction than the other direction, so they need to account for the two directions separately. Hence a special meter that knows how to do that.
This is from this morning. You can see that about 9:25 the load drops and then a few minutes later goes up again (nasty, high wattage things in the kitchen. But I do want my breakfast). When the load dips, so does PV, though it recovers (in this case in time for the next increase in load).
OK… could’ve been a cloud, but I see this correlation - sudden drop in load, followed by sudden drop in PV - quite often
NB! I cautiously raised the export limit to 50W, but it doesn’t seem to have made much difference that I can see on the graph, though my grid usage, on a sunny week, has dropped off just a little.
The lag is usually when load spike. The spike immediately goes to grid.
The inverter then takes it’s time to move that load to either battery or mppt.
The mppt can also lag, but I think its because the inverter again takes it’s time before starting to charge the battery.
I see the absolute best sun generation, when the battery is charging most of the time. If a load spike come in, it moves a lot faster to sun energy taking away from the generation going to the battery.
As for the 50w, I also found that does nothing. I had to minimum set mine to 100w.
A good test I had for myself is, I have this laser printer. It does this weird electricity spike every 30 seconds or something.
When I had the push back set to 0w or 50w, my energy generation was terrible. The 1st string would come on quick, but the 2nd string would always be idle. No one could tell me why. Then read about people having the push back set to 100w for some other reason but lets try.
I tried 50w first, but it was the same as if the inverter was set to 0w push back.
When I set it to 100w, I could initially not see the difference, but it became clear over time, that my pv generation became as solid and good as most other people who have other brand inverters. So I left mine now on 100w and I rarely worry about my pv generation now.
Lastly, my observations were done using Home Assistant, which allows me to see the values change every 3 seconds, as opposed to the goodwe software/website which is very difficult to see real time information.
When I’m sufficiently bored and aware of the dynamics of the household, I can use SolarGo to see these drop offs in real time.
The test for me would be the weekly electricity meter readings which show how much grid electricity I used. Those seem a little better with the setting at 50W. They’re not beating the best week I have on record, but I get a string of good weeks. But then just as you see a trend emerging you get a spell of overcast weather that makes a mess of what you hoped was a trend.
Nothing has blown up on the 50W setting, so I’m going to try 100.
