Solar Panels After 10 Years: How Much Output Do They Lose?

If your solar system has been sitting on your roof for around a decade, you may be wondering whether it’s still producing as much electricity as it should.

The good news is that 10-year-old solar panels do not automatically need replacing.

Solar panels are designed to operate for many years, but their generating capacity gradually reduces over time. This is known as solar panel degradation.

For many homeowners, the more important question isn’t: How old are my solar panels?It’s: Is my solar system still producing enough electricity for my home?

A system can be 10 years old and still perform well. Another system of the same age may have an inverter fault, damaged panel, new shading, maintenance issue or simply be too small for the household’s current electricity requirements.

That’s why MPV Solar recommends checking performance before assuming an older system needs replacing.

Solar panels gradually generate slightly less electricity as they age. There isn’t one degradation rate that applies to every panel. The rate depends on panel quality, technology, operating conditions and the manufacturer’s performance warranty.

Australian Government solar guidance notes that a common performance-warranty example is around 90% of original rated capacity at 10 years and 80% at 25 years, although individual products may offer different guarantees.

That means a small reduction in output after ten years can be completely normal. A major drop in generation, however, shouldn’t automatically be blamed on panel age. It may indicate another issue that needs investigating.

Solar panel degradation is the gradual reduction in a panel’s ability to generate electricity over time. Panels spend their lives exposed to: heat, sunlight, rain, wind, temperature changes, moisture and environmental conditions.

Over many years, these factors can contribute to gradual performance decline. This does not mean your panels suddenly lose a large amount of output when they reach their tenth birthday.

Degradation occurs progressively throughout the life of the panel. The important thing is to distinguish normal gradual degradation from an abnormal performance problem.

Ageing panels are only one possibility. Lower solar output can also be caused by:

• inverter faults
• damaged panels
• dirt or debris
• increased shading from growing trees or nearby development
• wiring or electrical problems
• monitoring faults
• equipment shutdowns
• changes to the household’s electricity consumption

Season and weather also significantly affect solar generation. A cloudy month compared with a sunny month isn’t evidence that the system has deteriorated.

If you’ve noticed a significant change in output, MPV Solar’s Solar Maintenance & Cleaning services can help assess whether the system is actually underperforming before you consider replacing equipment.

This is particularly important for systems installed around 10 years ago. Your solar panels may still be producing reasonably well, but your household electricity consumption may have increased significantly. Since the original system was installed, you may have added:

• more air conditioning
• pool equipment
• electric hot water
• induction cooking
• a home office
• additional appliances
• more people to the household
• an electric vehicle
• battery storage

A 5kW or 6.6kW solar system that suited the home years ago may simply no longer cover today’s electricity usage. That doesn’t necessarily mean the old panels have failed.

It may mean your home has outgrown the original solar system. MPV Solar’s Solar System Upgrades & Expansion Sydney service is designed to assess exactly this situation.

Don’t rely on the age of the system alone. Start by looking at actual performance.

Check Your Solar Monitoring: If your inverter or solar system has monitoring, review how much electricity it is producing. Look for:

• unexplained reductions in generation
• days with unusually low output
• periods where the system stops producing
• inverter error messages
• missing monitoring data

Where possible, compare similar periods from previous years rather than comparing summer generation with winter generation.

Check Your Electricity Bills: Your bill can also reveal useful clues. Look at how much electricity you are:

• importing from the grid
• exporting from solar
• using overall

A higher electricity bill does not necessarily mean your solar system has deteriorated. Your household may simply be consuming more electricity.

Have the System Inspected: If the numbers don’t look right, a professional system check can determine whether the issue is related to the panels, inverter, electrical equipment, shading or maintenance.

MPV Solar provides solar maintenance, system testing and performance checks for existing solar systems across Sydney.

On a 10-year-old solar installation, the inverter can be just as important as the panels. Many string inverter warranties are around 5 to 10 years, while solar panels generally have much longer performance warranties. This means an inverter may require attention or replacement before the panels themselves do.

If your panels are still in good condition but your inverter is failing, replacing the entire solar system may be unnecessary. Signs of inverter problems can include:

• fault codes
• repeated shutdowns
• no solar production
• communication errors
• inconsistent output
• monitoring problems

MPV Solar’s Inverter Specialists can diagnose inverter problems and determine whether repair or replacement is appropriate.

Not simply because they are 10 years old. Replacement becomes more worth considering when several issues occur together. For example:

• panel output has dropped significantly
• panels are damaged or unreliable
• the inverter also needs replacing
• the original system is substantially undersized
• modern panels could use limited roof space more effectively
• the system is difficult to expand
• older equipment is incompatible with your future battery plans
• several components require significant investment

If the panels are still performing well, keeping them may be the more sensible option. For the broader replacement decision, read MPV Solar’s Upgrade or Replace an Old Solar System?.

Yes, sometimes the problem isn’t failing panels. It’s simply not enough panels.

If your existing solar array is working properly but your household now consumes significantly more electricity, expanding the system can be a more targeted solution. This might involve:

• adding compatible solar panels
• installing an additional solar array
• adding another inverter
• upgrading the existing inverter
• redesigning the system around your current energy needs

Whether the existing panels and inverter can remain depends on compatibility, capacity, roof space, electrical infrastructure and current network requirements. Read Can You Add More Solar Panels to an Existing Solar System? for a detailed explanation.

Potentially. If the panels are still producing effectively but the inverter has failed or no longer suits the system, an inverter replacement may be all that is required.

It can also create an opportunity to consider whether the new inverter should support:

• additional solar panels
• future battery storage
• improved monitoring
• a larger overall system

Rather than replacing equipment unnecessarily, MPV Solar can assess which components are still delivering value and which are limiting system performance.

In many cases, yes. An older solar system does not automatically need new panels before battery storage can be added.

The more useful question is whether your system produces enough surplus solar electricity to regularly charge the battery.

If your older system still exports significant solar during the day, adding storage may be possible.

If the system struggles to meet daytime household consumption, you may benefit from additional solar before or alongside the battery.

Read Is Your Existing Solar System Big Enough for a Battery? to understand the generation-versus-storage decision.

For retrofit options, see Can You Add a Battery to an Existing Solar System? or explore Solar Battery Installation Sydney.

This is where the decision becomes more nuanced. Modern solar panels can offer greater output from the same amount of roof space than many panels installed a decade ago. But newer technology alone isn’t necessarily a reason to remove working equipment.

If your roof still has available space, it may be possible to expand the existing system. If roof space is limited and the original panels occupy the best areas of the roof, replacing lower-capacity older panels with higher-output modern panels may sometimes allow you to generate considerably more electricity from the available area.

The decision should consider: Existing system performance + available roof space + future electricity use + upgrade cost rather than comparing panel specifications alone.

A complete upgrade becomes more practical when the limitations of the existing system start stacking up. For example:

Panels are ageing + inverter needs replacing + system is too small + battery is planned + roof space is limited

At that point, investing repeatedly in an old configuration may be less practical than redesigning the system around how the home uses electricity today. A modern system can then be designed around:

• current household electricity use
• increased solar generation
• battery storage
• future electricity demand
• current inverter and network requirements

MPV Solar can compare targeted upgrades with complete system replacement through its Solar System Upgrades & Expansion Sydney service.

For a solar system around 10 years old, there are generally four pathways.

Repair: Best when the system is appropriately sized and the problem is a specific fault or maintenance issue.

Expand: Best when the existing equipment is performing well but the household needs more solar generation.

Upgrade selected components: Best when panels still perform but equipment such as the inverter is ageing or limiting future expansion.

Replace: Best when several ageing, performance, capacity or compatibility issues make continued investment in the old system less practical.

The right option depends on what your existing system is actually doing, not just its installation date.

If your solar system has been operating for around a decade, this is a sensible time to understand how it is performing. MPV Solar can assess:

• current solar production
• panel condition
• inverter performance
• historical system data
• household electricity consumption
• grid imports and solar exports
• available roof space
• potential solar expansion
• battery compatibility
• future energy requirements

From there, we can determine whether the system simply needs maintenance, an inverter replacement, additional panels, battery storage or a broader  upgrade.Start with MPV Solar’s Solar Maintenance & Cleaning services or explore Solar System Upgrades & Expansion Sydney.

Don’t replace it just because of its age. Have the performance checked first.

Send MPV Solar details of your existing system and a recent electricity bill. We can assess how the system is performing and whether repairing, expanding, adding battery storage or upgrading makes sense.