How to Know if Your Solar System is Underperforming

You’ve invested thousands in solar panels, but are they actually delivering the savings you expected? After installing over 13,500 solar systems across Queensland and South Australia, CJN Solar owner Craig Cannon has seen it all—and unfortunately, underperforming systems are more common than they should be.

The good news? Most issues are fixable once you know what to look for. Here’s how to tell if your solar system is pulling its weight or costing you money.

Check Your Energy Bills Against Expectations

The most obvious sign something’s wrong is when your electricity bills don’t match what you were promised. If your installer projected $400 quarterly bills but you’re still seeing $800, that’s a red flag.

Here’s what to do:

• Compare your bills: Look at the same quarter from before you installed solar versus now. You should see a dramatic reduction—typically 50-80% for a properly sized system.
• Check your usage hasn’t changed: Did you buy an electric vehicle, add a pool, or start working from home? Increased consumption could explain higher bills.
• Review your system size: A 6.6kW system should generate roughly 24-30kWh daily on the Gold Coast or Brisbane, and 22-28kWh in Adelaide. If your solar package was undersized for your needs, it’ll never meet expectations.

Your inverter or monitoring app should show daily production figures. Cross-reference these with what your installer promised at the point of sale.

Monitor Your Solar Production Data

Modern inverters from brands like Sigenergy and Hinen come with monitoring apps that track production in real-time. This data is goldmining for spotting underperformance.

What to look for:

• Consistent daily output: On sunny days, your production graph should show a smooth bell curve peaking around midday. Irregular spikes, drops, or flat sections indicate problems.
• Seasonal patterns: Production naturally drops in winter (June-August in Australia), but it should still be 60-70% of summer output. Anything less suggests issues.
• Sudden drops: If production suddenly halves or drops to zero, you likely have a faulty inverter, damaged panels, or a blown fuse.
• Gradual decline: A slow decrease over months or years could mean dirty panels, shading from new tree growth, or genuine panel degradation (though quality panels should only lose 0.5-0.7% annually).

After 15 years in the solar industry, Craig has seen countless systems underperforming simply because homeowners weren’t checking their monitoring apps. Set a reminder to review your production monthly.

Physical Signs Your Solar Panels Need Attention

Sometimes you can spot problems just by looking at your roof:

• Visible dirt or debris: Bird droppings, leaves, dust, and pollen can reduce output by 15-25%. On the Gold Coast and Adelaide, our relatively dry climates mean panels don’t self-clean as well as in higher rainfall areas.
• New shading: That tree you planted five years ago might now be casting afternoon shadows across your solar panels. Even partial shading on one panel can impact your entire string’s performance.
• Physical damage: Cracks, discolouration, or burn marks on panels indicate serious issues requiring immediate professional attention.
• Inverter warning lights: A red or orange light on your inverter (instead of solid green) means something’s wrong. Check your manual or call your installer.

If you’re in South East Queensland or Adelaide and notice any of these issues, it’s worth getting a professional assessment. CJN Solar offers system health checks for both systems we’ve installed and those from other providers.

Common Causes of Solar Underperformance

In Craig’s experience across 13,500+ installations, these are the usual culprits:

Incorrect Installation

Poor workmanship during installation—wrong panel orientation, suboptimal tilt angles, or loose connections—will plague your system for its entire life. North-facing panels at the right tilt should be standard in Australia, but budget installers sometimes cut corners.

Inverter Faults

Inverters typically last 10-12 years (warranties vary by brand). If your system is approaching this age and production is dropping, the inverter may be failing. This is particularly common in harsh Australian conditions if ventilation is poor.

Dirty Panels

As mentioned, dirt accumulation is the most common—and most easily fixed—issue. A professional clean every 12-18 months keeps panels operating at peak efficiency.

Grid Issues

Occasionally, your local electricity network might be limiting your solar export during peak production times. This is becoming more common in areas with high solar penetration. Check with your energy retailer if you suspect this.

Battery System Problems

If you’ve got solar batteries installed, issues with the battery management system or incorrect settings can prevent your system from cycling properly. Every CJN Solar battery installation includes Powwow VPP integration, which helps optimise performance and can flag issues early.

What to Do if Your System is Underperforming

First, don’t panic. Most issues are fixable:

1. Contact your installer: If you’re still within warranty (typically 5-10 years for workmanship, 10 years for inverters, 25+ for panels), get them out to assess the problem at no cost.
2. Get a second opinion: If your original installer has gone out of business or is unresponsive—sadly common in the solar industry—contact a reputable local company like CJN Solar for an independent assessment.
3. Document everything: Keep records of your production data, bills, and any communication with installers. This helps if you need to make warranty claims.
4. Consider an upgrade: If you’ve got an old system (8+ years), sometimes upgrading to modern panels and inverters delivers better long-term value than endless repairs.

For Queensland customers, remember that the state’s solar rebates and interest-free loans can help offset upgrade costs, making it more affordable to replace underperforming systems.

Get Your Solar System Performing at Its Best

Your solar investment should be saving you money year after year, not causing headaches. Whether you’re on the Gold Coast, Brisbane, or Adelaide, CJN Solar can help diagnose and fix underperforming systems.

With 15 years of experience and over 13,500 systems installed, Craig Cannon and the CJN Solar team know exactly what to look for—and more importantly, how to fix it. We work with premium brands like Sigenergy, Hinen, TCL, Tongwei, Jinko, and Trina to ensure reliable, long-term performance.

Not sure if your system is underperforming? Get a free quote or try our solar calculator to see what your system should be producing. Call CJN Solar on 1300 969 574 or email info@cjnsolar.com.au for a no-obligation system health check.

Your solar panels should be working hard for you—let’s make sure they are.