Hey guys. Looking for some advice. Looking to add 30-40 panels to my business building. We're on single phase and using 3000 to 4000kwh per month. During work hours the building is using 40A of power consistently and peaks at 55A due to the air-conditioning. With the current panel pricing it makes sense to put in a grid tied system to assist with the load during the day and bring down our electrical bill, especially with the eskom hike coming. 

My question is, what inverter do you guys think will be best suited? I would like to be investing under 100k and have no need for battery backup. We have a 8kva generator for any outages. I really just need a recommendation on a grid tied inverter to use that's reliable and has a decent app to monitor. 

15kW to 20kW on one single phase inverter is not common. If you go for multiple inverters, you will need a main meter and communication system. You could also go for micro-inverters. 

Go for the 16kW Sunsynk and run it without a batteries.

36 minutes ago, frivan said:

15kW to 20kW on one single phase inverter is not common. If you go for multiple inverters, you will need a main meter and communication system. You could also go for micro-inverters. 

Go for the 16kW Sunsynk and run it without a batteries.

A single 16kw inverter might not cover the 4000kwh per month. 6 x 5kw full hybrids are now so cheap that as you suggested one just use the grid tied function with no batteries and provide the best ROI. 

@cp69 I think your budget of R100k for 30 panels and enough inverter power to cover the 4000kwh a month is too low even at current low prices. 

27 minutes ago, Scorp007 said:

A single 16kw inverter might not cover the 4000kwh per month. 6 x 5kw full hybrids are now so cheap that as you suggested one just use the grid tied function with no batteries and provide the best ROI. 

@cp69 I think your budget of R100k for 30 panels and enough inverter power to cover the 4000kwh a month is too low even at current low prices. 

Sorry I should've been clearer there. I think I just need the solar to cover 2000-2500kwh per month of the electrical bill. Leaving a balance of 500-1000kwh to pay for. So I was thinking of 30 panels and a 10kw inverter which I can always expand on later. The sunsynk 10kw has 70A passthrough so it should handle the loads? Or to be safe use 2 X 8kw. Or the 16kw. Or 3 X 5kw grid tie inverter. Or micro inverters. I just can't see which is the better route to go. I just can't throw 150k at it for the easiest solution 

 

12 minutes ago, cp69 said:

The sunsynk 10kw has 70A passthrough so it should handle the loads?

A grid-tie inverter is typically installed in parallel with loads. Passthrough is not important then.

You say you have a generator but I would be surprised if there are no adverse effects with an outage. A hybrid inverter needs to be installed between critical loads and the utility. Passthrough is important in this case.

32 minutes ago, frivan said:

A grid-tie inverter is typically installed in parallel with loads. Passthrough is not important then.

You say you have a generator but I would be surprised if there are no adverse effects with an outage. A hybrid inverter needs to be installed between critical loads and the utility. Passthrough is important in this case.

I agree on this one. The grid tied just places it's power on top of the grid. It is in parallel and produces pure based on the PV available up to the inverter maximum. 

Also they tend to be so reliable that the APP does not have to be fancy as with a full function hybrid where the battery needs to be checked from time to time. 

Grid tied only inverters are being sold by 1st time buyers at very low prices. I have not seen any post of a Solis 4g mini giving problems. They are super reliable. 

At prices on offer 2nd hand the ROI without panel cost can be as low as 1 year. 

The hybrid without battery is then not installed between the critic loads and the utility but in parallel to the grid. 

Edited February 22, 20251 yr by Scorp007

32 minutes ago, Scorp007 said:

I have not seen any post of a Solis 4g mini giving problems

I was very happy with my Solis. I went for a dual MPPT 4G and not the mini. 

I see the 6g version at 4.6kW is common and relatively inexpensive. Just not sure if three inverters with CTs to the municipal supply is practical. There are export managers for Solis but I don't have experience.

Edited February 22, 20251 yr by frivan

12 hours ago, Scorp007 said:

I agree on this one. The grid tied just places it's power on top of the grid. It is in parallel and produces pure based on the PV available up to the inverter maximum. 

Also they tend to be so reliable that the APP does not have to be fancy as with a full function hybrid where the battery needs to be checked from time to time. 

Grid tied only inverters are being sold by 1st time buyers at very low prices. I have not seen any post of a Solis 4g mini giving problems. They are super reliable. 

At prices on offer 2nd hand the ROI without panel cost can be as low as 1 year. 

The hybrid without battery is then not installed between the critic loads and the utility but in parallel to the grid. 

Ok great appreciate this feedback guys. Grid tie definitely seems to be the way to go as I want the panel power to only assist on top of the grid feed. I don't want the loads to be fed through the inverter. This exercise is mainly to bring down our electrical bill and to assist with power as we do sometimes trip our 60A breaker on a hot day when all 7 aircons are running. I'm thinking the Solis grid tie option is the way to go, I have a Solis s6 pro hybrid at my home installation and it's been flawless for the last 16months.

Edited February 23, 20251 yr by cp69

1 hour ago, cp69 said:

Ok great appreciate this feedback guys. Grid tie definitely seems to be the way to go as I want the panel power to only assist on top of the grid feed. I don't want the loads to be fed through the inverter. This exercise is mainly to bring down our electrical bill and to assist with power as we do sometimes trip our 60A breaker on a hot day when all 7 aircons are running. I'm thinking the Solis grid tie option is the way to go, I have a Solis s6 pro hybrid at my home installation and it's been flawless for the last 16months.

Can't really comment without understanding the power demand of the business in greater depth. I think that just pure grid-tie is the wrong way to go. If you consider the Eskom tariff re-structuring that would be likely to force you into a fixed fee and time-of-use tariffs over the next period, then a hybrid inverter with possibility for battery backup will help you to manage your generation and demand much better, and give you flexibility down the road. I'd think, the 16kW Sunsynk/Deye would be best if you want up to 40 panels, but at least a 12kW could also be useful if you're sticking to 30 panels. Writing this to you as we've got the return of Stage6 loadshedding.

Edited February 23, 20251 yr by GreenFields

8 hours ago, GreenFields said:

Can't really comment without understanding the power demand of the business in greater depth. I think that just pure grid-tie is the wrong way to go. If you consider the Eskom tariff re-structuring that would be likely to force you into a fixed fee and time-of-use tariffs over the next period, then a hybrid inverter with possibility for battery backup will help you to manage your generation and demand much better, and give you flexibility down the road. I'd think, the 16kW Sunsynk/Deye would be best if you want up to 40 panels, but at least a 12kW could also be useful if you're sticking to 30 panels. Writing this to you as we've got the return of Stage6 loadshedding.

Yeah I hear you about the Eskom hikes looming and no doubt panel prices will soon go up in price too. Because it's a business on single phase and we only require power during working hours my thinking would be to put in a system now that is scalable. We have have 2 X 8kva generators on site which do run everything but we generally only run one of them on essentials when it's load shedding. So then I don't really see the need for battery backup. I'm just not sure if a sunsynk/deye running in Grid Tie mode works exactly the same as a grid tie inverter. Is it possible to just feed the pv generated power back to the mains dB without any loads running through the inverter?

Edited February 23, 20251 yr by cp69

22 hours ago, cp69 said:

Is it possible to just feed the pv generated power back to the mains dB without any loads running through the inverter?

Yes. Grid tie inverters can only inject current against a reference grid. Off grid inverters can only generate a local grid (downstream). Hybrid inverters can generate a local grid and then sync this grid with the municipal grid for import or export of power. There is nothing wrong with exporting all solar power and not having load and battery connected on the Sunsynk/Deye inverters.

On 2025/02/23 at 8:47 PM, cp69 said:

 Is it possible to just feed the pv generated power back to the mains dB without any loads running through the inverter?

Yes as per the reply from @frivan. Thats why the proposed inverter is a hybrid. It runs on either grid or battery power. You can thus run it on the grid tied mode with no back up. No need to connect any loads to the UPS output side as the grid tied in and out is run from the grid input back to the DB from solar generated AC.

On 2025/02/23 at 8:47 PM, cp69 said:

Is it possible to just feed the pv generated power back to the mains dB without any loads running through the inverter?

As the other 2 comments already stated, yes, however, be aware, that neither the Solis as far as I know, nor the Deye/Sunsynk, will be able to feed power to the grid end, when the grid has disappeared...

Ok great. This is very very helpful. So going with a 16kw single phase sunsynk will do the job and be future proof if I ever want to add batteries. 

On 2025/02/25 at 7:02 AM, Kalahari Meerkat said:

As the other 2 comments already stated, yes, however, be aware, that neither the Solis as far as I know, nor the Deye/Sunsynk, will be able to feed power to the grid end, when the grid has disappeared...

Question on this. My understanding is that when I'm using a deye/sunsynk in grid tied mode the panels will do the heavy lifting and the balance needed will come from the grid. BUT when there is load shedding the panels won't help at all because the inverter will shut down. SO my thinking is that the generators should be connected to the inverter and would kick in to provide the 'grid' to the inverter. The panels would be back in operation and the generators would just be idling(on a sunny day)?? Am I on the right path?

Edited February 26, 20251 yr by cp69

5 minutes ago, cp69 said:

Ok great. This is very very helpful. So going with a 16kw single phase sunsynk will do the job and be future proof if I ever want to add batteries. 

Questing on this. My understanding is that when I'm using a deye/sunsynk in grid tied mode the panels will do the heavy lifting and the balance needed will come from the grid. BUT when there is load shedding the panels won't help at all because the inverter will shut down. SO my thinking is that the generators should be connected to the inverter and would kick in to provide the 'grid' to the inverter. The panels would be back in operation and the generators would just be idling(on a sunny day)?? Am I on the right path?

Bear in mind if this works and the generators are just idling you will find they have white smoke which is not good for them if they are diesel generators. If diesel they are most happy around 60-75% of their rated power. 

12 hours ago, cp69 said:

the panels won't help at all because the inverter will shut down.

only if you have no batteries, if you have batteries, the essential/UPS side of the inverter will keep on working from the solar panels with support from the battery/ies... so, you would not necessarily need huge battery capacity to stay up and running if the solar, supplies plenty, including adding a charge to the battery...

12 hours ago, cp69 said:

generators would just be idling(on a sunny day)?? Am I on the right path?

yes and no, it depends on the generator, if it/they can keep the frequency stable as well as the Voltage, then yes, the inverter may well be happy with this setup...

On 2025/02/25 at 8:52 PM, cp69 said:

The panels would be back in operation and the generators would just be idling(on a sunny day)?? Am I on the right path?

That is not a good idea.

The generator can not "consume" or "accept" power from the solar.

So if load power is smaller than PV power, the generator will have problems. Perhaps black smoke.

Personally, the Inverter without "some" Battery backup is not such a good idea. When the grid fails - an believe me, it will - then the Inverter has no way of alerting the Gennie to start automatically. Even if you have separate "grid-loss" signal box to start the Gennie, there will be quite a few seconds (30?) before the Gennie's power is stable. Because your Inverter is dead, it will take even longer to wake up, + you would need an ATS between Gennie and Inverter. Perhaps you already have those items, as that is probably how it is operating today.

Even if you Factory/Premises operations can tolerate the 2 dips in power for 1 bout of Load Shedding/local Grid failure, most Electrical devices don't like frequent power drops, and it will shorten their lifetime.

Running the Gennie 24x7 is never a good idea, and the cost of doing that should easily pay for a small, say 5kWh battery.

Yes, at full tilt, it may only last a few minutes, in which time the Gennie can recover and switch. Most modern Inverters have this function built-in these days.

I would design the system size such that the PV & Inverter can cover the whole load + a bit in reserve. The Battery size just the minimum to cover the switchovers.

Go for the biggest Inverter model, as I seen parallel (Master & Slave) installations are a bit more cumbersome to install/maintain/manage, and should be a last resort.

As mentioned, if you reach the top end of an Inverters capacity, there's always a few micro-inverters (AC Coupled) that can add 2kW steps of AC into the mix.

Pity that the 125% rebate for commercial solar installation has ended 1 March 2025.

Start with getting the basic's right. The 16kW SS mentioned is probably the right choice. It can handle the full load. It can support 20800W of PV, so I would prioritize the budget for Inverter (+-R52k) then 5kW battery (+-R20k), and the rest (R30k) into PV/Installation.

Even if the budget then only allows for 10kW of PV, that fine, as the next time you have budget available, just add more PV. If you choose a too small inverter (say a 10kW), then you will need to fork out more R's to do a forklift, or even to expand the existing system.

In any case, allow for ample space for expansion, irrespective of which way you go.

Good Luck.

On 2025/02/25 at 9:52 PM, cp69 said:

SO my thinking is that the generators should be connected to the inverter and would kick in to provide the 'grid' to the inverter. The panels would be back in operation and the generators would just be idling(on a sunny day)?? Am I on the right path?

Theoretically you should be able to connect the generator on the gen input and the solar shouldn't export to it. You could also wire in some non-essentials as baseload for Diesel generators.

Practically frequency control might be an issue.

In line with @Sidewinder but I'd suggest a Greenrich 1.5C 7.5kW battery, the 8kW generator on the AUX port with auto-start, then around 35A of the 40A office loads designated as core essential loads for the load port, and then the rest of the office loads and the aircons on the non-essential grid port. Use the16kW Deye with around 20*550W (=11kW) panels connected at first, expandable to more later. Basically, rather take fewer panels in the beginning and divert that cost to at least the one battery. I know the goal is to save money more than anything else, but this will give you a more robust, stable system.

Beyond that I'd suggest doing a study of your grid usage, ie. let it be measured over a couple of days, or just explain what loads you're running and when. Just considering that 4000kWh per month on a 1P line running at 55A full-power all day, in an 8-hour work day Monday-to-Friday, you should only be using 2225kWh during a normal month during work hours. How are you reaching 4000kWh pm? Just afraid some info is missing that could be useful in sizing the system.