Hi all,
I recently had a FoxESS system installed (H3-5.0-Smart Inverter and EQ4800-L9 batteries) just over a week ago. These are installed to my pre-existing 6.6kW solar panels with a Sungrow SG5KTL-MT_001_001 PV system (using Solar iCloud to monitor).
I'm concerned that I am not enjoying the benefits of the new solar battery system and my bill appears to have gone up more than previously on the first week (as shown on my electricity provider app). Our household average usage is usually average 550-590kWh per month.
My current setting is 'self use' with tariff set as following:
- Peak 1600-2100 Buy 0.42, off-peak 0900-1600 Buy 0.21 and mid-peak Buy 0.32; FIT 0.03 (sell)
I'm also concerned that the Sungrow PV system is not sharing the PV production figures hence not fully utilise the battery efficiently. Interestingly, I noticed the system charging and exporting to grid after sunset at current mode.
Are these normal? Any recommendations to save more buck or utilise the battery more?
Didn't the installers put a CT clamp on that system so the inverter can monitor it?
I have a very similar setup—a large FoxESS KH10 inverter and a 41.93kWh battery working alongside a pre-existing solar system. Based on what you’re describing, your installer likely missed a critical step in how AC-coupled systems "talk" to each other.
Here is what is likely going wrong and how to fix it:
1. The "Exporting after Sunset" Issue (The CT Clamp)
If your system is exporting to the grid after dark, your FoxESS inverter is likely "confused." It thinks there is excess solar production coming from your Sungrow, so it’s trying to push power out.
The Fix: Your installer must ensure the FoxESS CT clamp (or Smart Meter) is placed at the grid connection point (the main incoming power line), NOT just on the solar line. If it’s in the wrong spot, the FoxESS doesn't know what the whole house is doing and will dump battery power into the grid instead of saving it for you.
2. The Inverters aren't "Sharing" Data
In an AC-coupled system, the Sungrow and FoxESS don't usually talk to each other digitally. Instead, the FoxESS "sees" the Sungrow’s production as "negative load."
The Setting: Make sure your Work Mode is set to "Self-Use", but check that "Export Control" is configured correctly. If you want to maximize savings, you should set your Min SOC (State of Charge) to about 10% so you use as much of that battery as possible during those expensive 42c peak hours.
3. Why your bill went up
If the FoxESS isn't sensing the house load correctly due to a bad CT clamp placement, it might actually be charging from the grid during off-peak or mid-peak times without you realizing it, or failing to discharge when you're actually using power.
Recommendations for your installer:
Check CT Direction: If the clamp is on backward, the system thinks "Export" is "Import."
Enable AC-Coupling: Ensure the "AC-Coupled" function is toggled ON in the FoxESS advanced settings. This tells the FoxESS to look for energy coming from your Sungrow inverter.
Tariff Buffering: With a 42c peak, you should prioritize discharging the battery fully between 16:00 and 21:00.
I have a much larger battery bank, but the logic is the same: the FoxESS should only ever export to the grid once the battery is 100% full and the house loads are satisfied.
Here is what is likely going wrong and how to fix it:
1. The "Exporting after Sunset" Issue (The CT Clamp)
If your system is exporting to the grid after dark, your FoxESS inverter is likely "confused." It thinks there is excess solar production coming from your Sungrow, so it’s trying to push power out.
The Fix: Your installer must ensure the FoxESS CT clamp (or Smart Meter) is placed at the grid connection point (the main incoming power line), NOT just on the solar line. If it’s in the wrong spot, the FoxESS doesn't know what the whole house is doing and will dump battery power into the grid instead of saving it for you.
2. The Inverters aren't "Sharing" Data
In an AC-coupled system, the Sungrow and FoxESS don't usually talk to each other digitally. Instead, the FoxESS "sees" the Sungrow’s production as "negative load."
The Setting: Make sure your Work Mode is set to "Self-Use", but check that "Export Control" is configured correctly. If you want to maximize savings, you should set your Min SOC (State of Charge) to about 10% so you use as much of that battery as possible during those expensive 42c peak hours.
3. Why your bill went up
If the FoxESS isn't sensing the house load correctly due to a bad CT clamp placement, it might actually be charging from the grid during off-peak or mid-peak times without you realizing it, or failing to discharge when you're actually using power.
Recommendations for your installer:
Check CT Direction: If the clamp is on backward, the system thinks "Export" is "Import."
Enable AC-Coupling: Ensure the "AC-Coupled" function is toggled ON in the FoxESS advanced settings. This tells the FoxESS to look for energy coming from your Sungrow inverter.
Tariff Buffering: With a 42c peak, you should prioritize discharging the battery fully between 16:00 and 21:00.
I have a much larger battery bank, but the logic is the same: the FoxESS should only ever export to the grid once the battery is 100% full and the house loads are satisfied.
Thanks heaps! That's very helpful and I will contact the installer to look into those issues!
Btw, when you mentioned prioritize discharge the battery fully, does that mean to also set the force discharge power to higher value? Mine is currently at 5000W. I thought it has to be same to the inverter size. Please correct me if am wrong.
Btw, when you mentioned prioritize discharge the battery fully, does that mean to also set the force discharge power to higher value? Mine is currently at 5000W. I thought it has to be same to the inverter size. Please correct me if am wrong.
1. The 5000W Limit
You are correct—since you have an H3-5.0 inverter, its maximum output is 5000W (5kW). Setting your "Force Discharge" higher than 5000W won't do anything because the hardware physically cannot push more than 5kW into your home or the grid at once.
2. "Force Discharge" vs. "Self-Use"
You generally don't need to use the "Force Discharge" setting for daily savings.
Force Discharge: This tells the battery to dump power at a specific time, regardless of what your house is using. (Usually used if you’re getting paid a massive premium to export to the grid).
Self-Use (Recommended): In this mode, the battery will automatically discharge to cover your house loads up to 5000W. If your house is using 2000W, the battery provides 2000W. If you turn on the oven and usage jumps to 6000W, the battery provides its max (5000W) and you pull the remaining 1000W from the grid.
3. What I meant by "Prioritize"
Since your Peak rate is a massive $0.42/kWh, you want to ensure your battery is full by 16:00 (4 PM).
If your 6.6kW solar hasn't filled the battery by then because it's been a cloudy day, you might actually want to "Force Charge" the battery during your Off-Peak ($0.21) or Mid-Peak ($0.32) times.
That way, you are guaranteed to have a full battery to cover that expensive 4 PM–9 PM window. Even if you "bought" the power at 21c, using it to offset a 42c charge saves you 21c per kWh!
Summary for your settings:
Keep your max discharge at 5000W, but focus on your SOC (State of Charge) settings. I keep my Min SOC low so I can use every bit of my battery storage to avoid those peak grid prices.
You are correct—since you have an H3-5.0 inverter, its maximum output is 5000W (5kW). Setting your "Force Discharge" higher than 5000W won't do anything because the hardware physically cannot push more than 5kW into your home or the grid at once.
2. "Force Discharge" vs. "Self-Use"
You generally don't need to use the "Force Discharge" setting for daily savings.
Force Discharge: This tells the battery to dump power at a specific time, regardless of what your house is using. (Usually used if you’re getting paid a massive premium to export to the grid).
Self-Use (Recommended): In this mode, the battery will automatically discharge to cover your house loads up to 5000W. If your house is using 2000W, the battery provides 2000W. If you turn on the oven and usage jumps to 6000W, the battery provides its max (5000W) and you pull the remaining 1000W from the grid.
3. What I meant by "Prioritize"
Since your Peak rate is a massive $0.42/kWh, you want to ensure your battery is full by 16:00 (4 PM).
If your 6.6kW solar hasn't filled the battery by then because it's been a cloudy day, you might actually want to "Force Charge" the battery during your Off-Peak ($0.21) or Mid-Peak ($0.32) times.
That way, you are guaranteed to have a full battery to cover that expensive 4 PM–9 PM window. Even if you "bought" the power at 21c, using it to offset a 42c charge saves you 21c per kWh!
Summary for your settings:
Keep your max discharge at 5000W, but focus on your SOC (State of Charge) settings. I keep my Min SOC low so I can use every bit of my battery storage to avoid those peak grid prices.