Why Does My Solar Output Drop to 3.68kW?
Many homeowners notice their solar system generating more than 3.68kW before suddenly settling at around 3.68kW for part of the day.
At first glance, this can appear as though something has gone wrong.
In reality, this behaviour is often completely normal and is usually the result of how the inverter is designed or how the system has been configured.
This guide explains why solar output can appear to plateau around 3.68kW, what inverter clipping is and when you should seek professional advice.
Why Does My Solar Output Stop Increasing?
The solar panels on your roof generate direct current (DC) electricity.
Your home, however, uses alternating current (AC) electricity.
The inverter converts DC electricity from the solar panels into usable AC electricity for your property.
Every inverter has a maximum AC output rating.
Once this limit is reached, the inverter cannot increase its AC output further, even if the solar panels are capable of producing more DC power.
Why 3.68kW?
Many domestic solar systems in the UK use a 3.68kW inverter.
Historically, this output aligns with the standard export limit associated with many domestic installations connected under G98.
Although the solar array itself may be capable of producing significantly more electricity, the inverter will not export more AC power than its rated output unless a larger system has been installed and the necessary connection arrangements are in place.
What Is Inverter Clipping?
Inverter clipping occurs when the solar panels are capable of producing more electricity than the inverter can convert into AC power.
Rather than indicating a fault, clipping simply means the inverter has reached its maximum output.
This commonly occurs:
- During bright sunshine.
- Around midday.
- During cooler weather when solar panels operate efficiently.
Clipping is often visible on monitoring apps as a flat section on the power graph.
Is Clipping a Bad Thing?
Not necessarily.
Many solar systems are intentionally designed with a solar array that is larger than the inverter's AC output.
This approach can improve electricity generation during mornings, evenings and overcast conditions, even though some clipping may occur during periods of peak sunshine.
For many homeowners, the additional annual generation outweighs the relatively small amount of energy lost during clipping events.
Why Does My System Sometimes Start Above 3.68kW?
Some hybrid systems may display generation figures above the inverter's continuous AC output.
For example, when a battery is charging directly from the solar panels, the monitoring app may show:
- Electricity supplied to the home.
- Electricity charging the battery.
- Electricity being converted by the inverter.
Because some energy transfers occur internally within the system, the displayed figures can differ from the AC output exported to the property or the grid.
The exact behaviour depends on the inverter manufacturer and how the monitoring platform reports energy flows.
Does Battery Storage Affect This?
Yes.
Hybrid inverters can manage solar generation, battery charging and household demand simultaneously.
During periods of strong solar generation, energy may be:
- Used by the home.
- Stored in the battery.
- Exported to the grid.
How these energy flows appear in the monitoring app varies between manufacturers, and displayed values do not always represent the inverter's AC export alone.
Is My Inverter Faulty?
Usually not.
If your system consistently reaches around 3.68kW before maintaining that output, the inverter is often operating exactly as intended.
Possible signs of a fault would include:
- Unexpected shutdowns.
- Error messages.
- Significantly lower generation than expected.
- Frequent interruptions during normal weather conditions.
If you are concerned, your installer should be able to review the system's monitoring data.
Could a Larger Inverter Help?
Potentially.
Whether a larger inverter is appropriate depends on several factors, including:
- Solar array size.
- Existing connection agreement.
- Distribution Network Operator (DNO) requirements.
- Future battery storage.
- Export limitation arrangements.
Increasing inverter capacity is not simply a case of replacing the inverter and should always be professionally assessed.
How Zero Carbon Designs Around Clipping
A well-designed solar system balances:
- Annual electricity generation.
- Inverter efficiency.
- Household demand.
- Future expansion.
- Battery storage.
- Network connection requirements.
Rather than avoiding clipping altogether, professional designers consider whether a degree of clipping provides better overall annual performance.
This approach often results in greater energy generation across the year rather than focusing solely on maximum midday output.
Frequently Asked Questions
Why does my solar output stop at 3.68kW?
In many domestic systems, this is the inverter's maximum AC output and is completely normal.
Is inverter clipping harmful?
No. Clipping is a normal characteristic of many solar systems and does not indicate damage to the inverter.
Why does my app sometimes show more than 3.68kW?
Some monitoring platforms display combined energy flows, including battery charging, rather than only the inverter's AC output.
Can I stop clipping?
It depends. A larger inverter may reduce clipping, but this may require changes to the system design and DNO connection arrangements.
Should I contact my installer?
If the inverter is operating normally and no fault messages are present, clipping alone is usually not a cause for concern. If you notice unexpected behaviour or reduced generation, it is sensible to seek professional advice.
Concerned About Your Solar System's Performance?
If you've noticed your solar output levelling off around 3.68kW, it doesn't necessarily mean something is wrong.
Zero Carbon provides expert advice on solar performance, inverter sizing and battery storage, helping homeowners across Scotland understand how their systems operate and how to maximise long-term performance.
Contact our team today if you'd like us to review your solar installation.
