Emit Solar | Home Solar Panels | Easy Ownership
Your solar system was supposed to cut your electricity bill. So why does it seem like it’s saving less than it used to?. A drop in savings doesn’t always mean something is broken – but it may mean something has changed. There are more causes than most people realise.
What kind of drop are you seeing?
It usually falls in one of two patterns:
Savings fall sharply and suddenly.
Something likely changed, stopped working or got limited.
Savings reduce slowly over time.
Nothing may be “broken” but conditions have changed.
What could be causing it
Most solar savings changes come from one of these areas:
Each of these can cause either a sudden drop or a gradual decline.
Start with the pattern. Then narrow it down by area.
Sudden drop – what to check first
If your savings dropped sharply, something likely changed or stopped working.
Solar panels are typically wired together in “strings” – groups that feed into a single input on your inverter. If one string fails completely (due to a wiring fault, loose connector, or faulty junction box), every panel in that string stops contributing.
You could lose 20–50% of your system’s output instantly and not even know, because the inverter may still show as “operational.”
WHAT TO DO
Log into your monitoring portal and compare the output of each string. If one is at zero or significantly lower than the others, you likely have a string fault. Call your installer.
Solar systems have DC isolators, AC isolators, and circuit breakers. These are safety components that protect your system. Any of them can trip in response to a fault, power surge, or even a grid disturbance.
When they trip, your system may stop – sometimes silently.
A tripped breaker that nobody notices can cause weeks of zero generation while everything else looks normal from the outside.
WHAT TO DO
Check your DB (distribution board) and your inverter’s breakers. Look for anything in the OFF position. If you’re unsure which is which, ask your installer for a labelled diagram.
Inverters have configuration settings that control how much power they generate, export to the grid, what voltage range they operate within, and how they respond to grid fluctuations.
A common issue is an export limit being set too low – your system produces 5kW but is only allowed to export 2kW back, so the inverter is not generating at 100% of the system’s capability.
WHAT TO DO
Ask your installer to review your inverter’s active export settings and confirm they match your Solar ATAP approved capacity. Also check that the inverter firmware is up to date.
Sometimes the system is working fine – but the logger, Wi-Fi, or monitoring app has lost connection.
You stop seeing data. You assume something is wrong. Sometimes data gaps are just data gaps, not actual generation loss.
You might miss a real problem for weeks because nothing is alerting you.
WHAT TO DO
If the inverter looks fine but the app shows nothing, try to set up the Wi-Fi again or reboot the inverter.
When the grid voltage or frequency goes outside acceptable ranges, your inverter is legally required to disconnect from the grid. This is a safety feature, not a flaw – inverters must not export into an unstable grid.
This means that during periods of grid instability, your system may be cutting out repeatedly throughout the day, losing generation in the process.
Areas undergoing infrastructure work, industrial zones, or regions with frequent voltage fluctuations are more susceptible.
WHAT TO DO
Check your inverter’s event log for “grid overvoltage” or “grid fault” entries. If these are frequent, report them to TNB and ask your installer to review the grid connection voltage at your meter.
Gradual decline – what’s changed over time
If savings are slowly falling, it’s usually a combination of smaller changes.
This is one of the most overlooked reasons for shrinking savings – and it has nothing to do with your solar system at all. It’s about when you use electricity.
Solar savings come in two parts. The most valuable is direct self-consumption – using Solar Electricity the moment it’s generated (running your aircond, washing machine, or fridge during the day). Every unit you consume directly replaces one unit you’d have otherwise bought from TNB at the full tariff rate.
The second is export credit – sending excess solar to the grid and earning a credit based on your Energy rate, which is lower than what you pay TNB for imported electricity. It’s still a saving, but a smaller one per kWh.
So if your household routine changes – someone goes back to the office after working from home, school holidays end and the kids are out during the day, your direct self-consumption drops.
More of your solar output gets exported instead of used directly. Your system is still producing the same amount, but you’re earning less per unit because export credits are worth less than avoided import costs.
WHAT TO DO
Compare your monitoring data: has your self-consumption ratio dropped (less solar used directly, more exported)? If so, try shifting high-consumption tasks – laundry, dishwasher, EV charging, water heating – to daytime hours when the sun is shining. Even small shifts in routine can meaningfully improve savings.
Some charges apply when your monthly TNB import passes certain limits:
So if you usually import +/- 500kWh a month, but exceed 600kWh in another, then AFA and SST will apply. Charges like AFA are calculated from the first kWh, not just the units above 600kWh, so the bill increase can be significant.
These charges are based on the electricity you import from TNB. Solar exports do not reduce the imported usage used to calculate them.
So even if your solar system is generating normally, crossing these thresholds can make your bill jump and your solar savings appear lower.
WHAT TO DO
Compare your month-to-month usage patterns and see what taxes get charged after you cross the threshold.
Where possible, shift more usage to daytime hours so you use more solar directly and import less from TNB. This can help you stay below the thresholds and preserve more of your solar savings.
Under Solar ATAP, exports are credited based on the Energy charge – 27sen – 37sen per kWh, depending on your tariff tier.
When AFA changes (whether it’s a surcharge or discount), it adjusts the cost of electricity that you get from TNB, but does not change the rate you earn for exported Solar Electricity.
You may end up paying more per kWh, while still earning the same for exports.
The result: your bill can increase, while your export credits stay the same – reducing your overall savings.
WHAT TO DO
Review your bill’s AFA line item and compare it to previous months. If AFA has jumped and your export credit rate hasn’t moved proportionally, that’s the gap eating your savings.
Solar ATAP sets a Maximum Allowable Quantity (MAQ) – a cap on how much energy you can export to the grid within each month. The exact amount depends on your system size and the number of days in your billing month.
The MAQ is calculated as:
System capacity (kWac) x 5 sun hours x number of days in your billing period
Example:
A 5kWac system x 5 sun hours x 30 days = 750kWh
Once you hit your MAQ, any further exports are no longer credited – they go into the grid for free.
WHAT TO DO
Compare your export in your solar monitoring app with the credited export on your TNB bill (which reflects your MAQ).
If there’s a noticeable gap, you may be hitting your MAQ. Shift more usage to the daytime to maximise self-consumption instead of exporting excess energy.
Under Solar ATAP, export credits can only offset your Energy charge by a maximum of 100%. You cannot offset your network and capacity charges.
Once your Energy charge is fully offset, there’s nothing left for your credits to reduce.
If your solar system is oversized relative to your consumption, you may be hitting this ceiling regularly. You’re producing more than you can benefit from under the Solar ATAP.
WHAT TO DO
If your credits consistently zero out your bill with room to spare, consider increasing daytime electricity usage (EV charging, water heating) to soak up more self-generated power.
All solar panels degrade over time – it’s just physics. The industry standard is roughly 0.5% per year in output loss, though cheaper panels can degrade faster. After 10 years, a panel might be generating around 95% of what it did on day one.
It’s not a cause for alarm, but it does mean savings will very gradually reduce over the system’s lifespan.
WHAT TO DO
Nothing urgent. Compare your current generation to your system’s first full year of data. If the drop is greater than ~0.5% per year, something other than normal degradation may be at play.
Panels lose efficiency over time. Two of the more common culprits are microcracks – hairline fractures caused by physical stress, thermal cycling, or poor handling – and PID (Potential Induced Degradation), a voltage-related effect that eats into a panel’s power output, sometimes dramatically.
Both are invisible to the naked eye and show up as slow, steady drops in generation over months. A panel with PID can lose 30–50% of its rated output.
WHAT TO DO
Ask your installer to do a thermal imaging inspection. This can identify which panels are affected. PID can sometimes be partially reversed with PID recovery modules.
Shade is solar’s worst enemy. A new tree that’s grown taller, a neighbour’s extension, a water tank that was repositioned, or even a new telecommunications mast can cast shadows on panels that were previously clear.
One shaded panel may drag down an entire string – meaning one partially-shaded panel might cost you 40% of your string’s output.
WHAT TO DO
Compare your daily generation curve to last year’s, shade shows up as a dip at a consistent time of day.
Dust, bird droppings, leaves, and algae accumulate on panel surfaces over time and reduce how much sunlight reaches the cells.
WHAT TO DO
If you suspect build up is affecting performance, contact your installer. They can assess and arrange professional cleaning if needed (a service fee may apply).
Do note that every time someone climbs onto the roof, there is some risk of tile damage or water leaks. Always evaluate whether the generation drop is big enough to justify the work.
GOOD TO KNOW
Malaysia’s frequent rain helps keep panels relatively clean, but some stubborn dirt can still impact generation.
If you have yet to install, look for panels with “anti-shading” technology – such as the Aiko 670W panels that we deploy – as they help with more stubborn dirt such as bird droppings by bypassing the affected area(s) to minimise generation loss.
This surprises most people: solar panels actually generate less power when they’re very hot. Panels are generally rated at 25°C, but on a scorching Malaysian afternoon, panel surface temperatures can hit 50–60°C. That heat reduces efficiency by around 0.4% per degree above 25°C.
So during a particularly hot dry season, your panels might be generating 10-15% less power then the same amount of sunlight would have produced in cooler weather. It’s just physics.
WHAT TO DO
Not much you can do about the weather, but it’s worth knowing that this is temporary. Generation typically recovers when temperatures normalise.
If you are choosing a new system, look for panels with a better temperature coefficient – the closer the figure is to zero, the less output they lose in the heat.
For example, the Aiko 670W panels we deploy has a temperature coefficient of -0.26%/°C, compared with around -0.40%/°C for some conventional panels. This helps it retain more output on hot Malaysian roofs.
Quick diagnostic checklist
Before calling your installer, check:
If you’ve gone through this list and still can’t identify the cause, it’s time to call your installer. A good installer will pull the inverter’s event log and run a string-level performance test to isolate the issue.
Savings don’t drop randomly. Something changed:
The key is knowing which.