A 8kw grid tie inverter can contribute 8kw (lets say) to the 16 kw load, while the grid supplies the balance.

I think everyone is getting confused because of the assumption that electricity can only flow in one direction.

So from my understanding, the grid tie inverter rating needs to match to the solar panels. If you have a 3,6kW inverter and 10kW worth of panels, the inverter will only be able to convert the 3,6kW. So the size of the inverter needs to match to the size of the panels.

On the load side I would imagine that the grid tie inverter has nothing "under" the inverter as is the case with an off grid inverter but rather all the power generated is "pushed back" to the loads that require the power. 

I guess its the same concept with a Pure Hybrid inverter. If you have a 5kW inverter and your panels generate 4kW but your load is only 2kW, the remaining 2kW will get pushed back to the other loads not under the inverter even if those loads are 10kW

 

As @GreenFieldsalso said his final piece, I bow to the great experts on this forum.

4 hours ago, hoohloc said:

This still confuses me, A Sunsynk is a grid tied inverter. Are you saying you can power an 8kw load from a 5kw sunsynk by blending grid and solar?😁

Yes it can. 35 amps of passthrough on the 5kw sunsynk. Not that i would recommend going that high as you should be splitting the large non essentials onto the non load side of the inverter.

Here is a graph of my 5kw inverter working the most it has in one day ,you can see where it blends in from the grid.

5 hours ago, hoohloc said:

This still confuses me, A Sunsynk is a grid tied inverter. Are you saying you can power an 8kw load from a 5kw sunsynk by blending grid and solar?😁

Yes you can.
Remember that a grid tied / hybrid inverter can feed back to the grid.
If the load is in the "Grid" side, excess Solar capacity can be "blended" to the grid side to support a large load.
The 5kW inverter will allow a max of 5kW to be fed to the grid.
So 5kW from Solar + 3kW from Grid.
 

Edited February 2, 20224 yr by system32

5 minutes ago, system32 said:

Yes you can.
Remember that a grid tied / hybrid inverter can feed back to the grid.
If the load is in the "Grid" side, excess Solar capacity can be "blended" to the grid to support a large load.
The 5kW inverter will allow a max of 5kW to be blended.
So 5kW from Solar + 3kW from Grid.
 

I think I need to rephrase the question. Can a 5kw grid tie inverter power 8kw load if all that load is on the UPS side of the inverter? There is a reason why you have 5kw and 8kw inverter, but I can't seem to get my point through. Do you agree with me, that if that was the case, you wouldn't have bought an 8kw inverter?

3 hours ago, hoohloc said:

I'm glad someone gets this, and this is where my argument was. All those inverters that he mentioned, will trip if you go over their rated out put power

Because it is only a "Grid Tied" inverter, it should not trip if the load is greater than it's rated power. The excess that the load requires will be supplied by the grid(Eskom).

What it's rating means, is it can only supply 3kW into the load / grid.

The more advanced "Hybrid Parity (Super) Inverters" (SunSynk, etc) are two way inverters, with essential (UPS), non essential (grid tied), Aux ports,etc. These are in a different class, and more expensive.

3 hours ago, hoohloc said:

Ask your friend if he can draw 16kw out of his 8kw inverter

With the SunSync 8.8 kW, you can blend (solar / battery) / pass-through (grid) 12 kW to the essential (UPS) side of the inverter, as long as you have grid. During load-shedding, the essential (UPS) side of the inverter can only supply power according to the rating of the inverter, i.e. 8.8 kW, and all non essential (grid tied) loads are not supplied. 👍

No matter what inverter we have, during load-shedding, we all smile while our poor neighbors moan. 😂

Edited February 2, 20224 yr by TimCam

29 minutes ago, TimCam said:

No matter what inverter we have, during load-shedding, we all smile while our poor neighbors moan. 😂

As you say it, it's loadshedding right now over here, utter darkness looking out over the street/area. might even get the telescope out, it's a nice 8" newtonian, less light pollution. Of course my outside lights will have to go off. 

Edited February 2, 20224 yr by Nitrious

Just as many installers think all inverters must have batteries so a numbers of members are also latched on the fact that the grid tied inverter will trip if the load exceeds its rating. 

All that will happen when say you have 5kw of panels and the inverter is 3kw it will clamp it's output that it can generated on top of the grid at 3kw. No tripping. If on the other hand you get cloud and the PV is only 1kw on this 3kw grid tied it will only generate 1kw towards the load. The rest is drawn from the grid. 

The CT is used to prevent export and not to trip the prepaid meter. 

Normally one would match the panels to the inverter but you don't have to. You just need to ensure you have the minimum voltage to start the grid tied. This can be as low as 60V and 2 x 60 cell panels. If these 2 x 270W panels are connected then even the 3kw inverter cannot add more than 540W on top of the grid. 

Surely what has been said is clear enough to understand if one is prepared to except the actual way a grid tied works. Hybrids if true hybrids can then also have the back up side to assist when grid is off. Also no need to change the grid tied if installed. One can just add the back up via a 2nd inverter. 

6 hours ago, Nitrious said:

A 8kw grid tie inverter can contribute 8kw (lets say) to the 16 kw load, while the grid supplies the balance.

Just to make it clear for some. True provided you have panels that are producing the 8kw for the grid tied to generate. 

10 hours ago, hoohloc said:

I think I need to rephrase the question. Can a 5kw grid tie inverter power 8kw load if all that load is on the UPS side of the inverter? There is a reason why you have 5kw and 8kw inverter, but I can't seem to get my point through. Do you agree with me, that if that was the case, you wouldn't have bought an 8kw inverter?

A grid-tied inverter does not have a UPS side.

The sunsynk 5kw can pass-through 35A, so yes, you can have 8kW connected to the UPS output without it tripping (as long as you have grid as well)

Grid tie is a cost effective solar system with no batteries and relatively simplified installation used in countries with a stable power utility to export power during the day, get credits, only to use them at night and thus have a net effect of a zero power bill.

an interesting project is occurring in Australia called the community battery, so this large battery is charged through grid tie during the day, and is then used at night by the same community.

fast forward to sa, no load shedding protection, almost zero realistic export tariffs to be found if at all,  and fixed access fees to ensure the money still comes in. aka there's almost no way to have that grid tie zero balance bill. I've only found 1 person managing to do this so far, if anybody else knows someone who has managed to have a zero power bill through grid tie export, please  mention it.

as things stand, an inverter with batteries, panels all sized accordingly, along with load reduction measures of choice (solar geyser, heat pump, gas hob etc.) and no export seems to give the best roi and best continuation of lifestyle, while shielding from the inevitable upwards trend of power pricing.   

my thoughts on grid tie.

Edited February 3, 20224 yr by Nitrious

27 minutes ago, Nitrious said:

as things stand, an inverter with batteries, panels all sized accordingly, along with load reduction measures of choice (solar geyser, heat pump, gas hob etc.) and no export seems to give the best roi and best continuation of lifestyle, while shielding from the inevitable upwards trend of power pricing.   

This ^^^^
 

In my case I have a off grid to backup my essential loads, I am looking for the cheapest way to add panels to reduce my bill

Yes I agree but one can spend so much time to achieve a zero bill but when you decide let's use the Sunsynk in grid tied configuration and can go without grid for the time it takes to change the setting to USE BATTERY it is a great system.

Keep the batteries charged for periods like now.

I think we tend to want a seamless system via back up for the 2 hours a week we get LS. I'm not saying it won't get worse but for now I cope very well with my cheap grid tied and a separate back up that can keep the batteries charged from the AC the grid tied generates.

This shows how a grid tied does not trip when you have more panels than the output of some grid tied inverters. It will just clamp the output at the rating. 4.5kw in this case after 10h00. A great way of getting more power early and late in the day. My grid tied does not even have a overload to trip. If something goes wrong it will just switch off.

55 minutes ago, Nitrious said:

I've only found 1 person managing to do this so far, if anybody else knows someone who has managed to have a zero power bill through grid tie export, please  mention it.

I know a number of people that get close to 0, some of them even do it legally!

4 minutes ago, P1000 said:

I know a number of people that get close to 0, some of them even do it legally!

jamming a stick in your wheel meter doesn't count 😀

but also good to know there are others, maybe a general description of how the legal ones did it, so it can be used as a template for others here to follow. Should actually be a topic all its own. 

Edited February 3, 20224 yr by Nitrious

21 minutes ago, MNK1234 said:

In my case I have a off grid to backup my essential loads, I am looking for the cheapest way to add panels to reduce my bill

If you don't have a Conlog prepaid the grid tied can be added to your current inverter if the current is not already a true hybrid. A grid tied can have a pay back as low as 2 years. Size has a major effect as well as if you can actually use the power during the day. Aircons, geyser, pool pump and the little fridges do use. In my case fridges account for 30% and heat pump also 30% of consumption.

36 minutes ago, MNK1234 said:

In my case I have a off grid to backup my essential loads, I am looking for the cheapest way to add panels to reduce my bill

the cheapest way to do this may not always be apparent.

option 1 : buy second hand, there's always someone upgrading.

option 2 : leverage your bond, and access funds, the monthly will be around R1k per month per R100k accessed.

option 3 : other financial leveraging, usually expensive, aka rent to own etc etc

So to this end of a cost effective solar system with great roi, the following happened

my 10kwh battery was born

I have access to a (practically, over 200,000) unlimited supply of 360w panels (and other sizes) for around R1k each, putting a 5kw panel array at around R15k

Edited February 3, 20224 yr by Nitrious

@Scorp007, what make of grid tied inverter do you have ?

13 hours ago, TimCam said:

What it's rating means, is it can only supply 3kW into the load / grid.

I look at this a bit differently and its a bit more complicated if batteries are involved.

A 5kW inverter is rated to only CONVERT DC from panels to 5kW A/C...Its all about DC to AC conversion. How much the inverter can provide to load(+battery) may be higher than the rated DC to AC conversion rating.

E.g. my Goodwe is rated at 5kW, it regularly provides close to 6kW of power when it provides to my house and the battery (DC bus, DC to DC)...My entire house load + batteries can often get to 9kW when the kettle, drier etc. are all on at the same time...BUT, the inverter will still only CONVERT from PV to 5kW AC power.

So, to put it simply the rating of an inverter irrespective of batteries,  is what PV (DC) it can covert to AC...

And your panels should fit your Inverter (i.e choose inverter first) unless you have a restriction on space for panels (or panel capacity)...I'm not sure people buy panels first and then decide on the inverter to fit the panels!

Sorry, had to think this through for my own sanity after reading the above posts...

2 hours ago, Tariq said:

@Scorp007, what make of grid tied inverter do you have ?

Solis 4G mini. What a joy to connect 5 wires and no changes to a DB and it sits there silent and doing what it was designed to do.

My payback for whole system less than 3 years.

I know of someone with Sunsynk 5kw and 6.5kw panels without a battery and his indication is a pay back of less than 2 years.

Edited February 3, 20224 yr by Scorp007

4 hours ago, Nitrious said:

Grid tie is a cost effective solar system with no batteries and relatively simplified installation used in countries with a stable power utility to export power during the day, get credits, only to use them at night and thus have a net effect of a zero power bill.

an interesting project is occurring in Australia called the community battery, so this large battery is charged through grid tie during the day, and is then used at night by the same community.

fast forward to sa, no load shedding protection, almost zero realistic export tariffs to be found if at all,  and fixed access fees to ensure the money still comes in. aka there's almost no way to have that grid tie zero balance bill. I've only found 1 person managing to do this so far, if anybody else knows someone who has managed to have a zero power bill through grid tie export, please  mention it.

as things stand, an inverter with batteries, panels all sized accordingly, along with load reduction measures of choice (solar geyser, heat pump, gas hob etc.) and no export seems to give the best roi and best continuation of lifestyle, while shielding from the inevitable upwards trend of power pricing.   

my thoughts on grid tie.

I have a friend in Centurion Gauteng who feeds back into the grid  for energy consumed at night. he only pays to have the Eskom meter linked to his home.

 

@Scorp007

Solis 4G mini. What a joy to connect 5 wires and no changes to a DB and it sits there silent and doing what it was designed to do.

I would have thought live, neutral and ground, what are the other two wires.

 Also, as you said, no issues with setting it up, I have a client that says they don’t need batteries, so was thinking about a Solis

2 hours ago, Tariq said:

@Scorp007

Solis 4G mini. What a joy to connect 5 wires and no changes to a DB and it sits there silent and doing what it was designed to do.

I would have thought live, neutral and ground, what are the other two wires.

 Also, as you said, no issues with setting it up, I have a client that says they don’t need batteries, so was thinking about a Solis

The other 2 wires are those from the series string of panels. One uses the normal surge arrestors. Disconnect via MCB of 15A. This can be 4 wires if the unit bought is 3.6kw and over and has 2 X MPPTs for 2 strings. Panels are not used in parallel strings per MPPT as it will exceed the current allowed. The only known problem I have heard is the voltage has been pre-set to 260V and and if the grid exceeds this it will switch the MPPT off. This is part of the grid code used and a munic problem as the inverter is working as it should. 

The biggest job as far as settings go is to add the CT clamp as the standard config is to allow export to grid and setting up the WiFi dongle for APP and Web stats. WiFi dongle is a option as is the CT clamp. 

Edited February 3, 20224 yr by Scorp007