Guides · Faisalabad, Lahore, Punjab
Why Is My Solar System Producing Less Than Expected?
Short answer
When a solar system is producing less than expected, the cause is usually one of four things: the season and weather, dirt or shade on the panels, the inverter holding output back (export limit, full battery or heat), or a fault such as one string not working. Start by comparing the right numbers, then work through the safe checks below. If one string or one inverter shows zero, or the drop is sudden and stays on clear days, call your installer.
First, make sure the comparison is fair
Many "low production" worries come from comparing the wrong figures.
- Compare month with month, not month with the yearly average. A Punjab system makes far less in a foggy December than in a clear April. Our guide to how many units a 5, 10 or 15 kW system produces in Punjab gives indicative yearly ranges and explains the seasonal swing.
- Use units (kWh), not kW. The app's live kW figure at one moment says little. Look at daily and monthly kWh.
- Compare like with like. The same month last year, or a neighbour's similar system on a similar roof, is a better benchmark than a sales brochure.
- Check what the estimate assumed. An estimate may assume a south-facing roof, no shade and clean panels. If your roof differs, your output will too.
Once the comparison is fair, a real shortfall is worth investigating.
Why production is low
Dirt and smog
Dust layer on the glass
Shade
Trees, tanks or new buildings
Faults
A string or connector not producing
Safety first
This guide covers checks an owner can make by looking, not by touching wiring. Panels produce DC voltage whenever light falls on them, even with the grid and inverter switched off.
- Do not open the inverter, the DC isolator box or junction boxes, and do not pull MC4 connectors.
- Do not climb onto a roof without a safe access point and someone with you.
- Leave anything burnt, cracked, melted or wet to a qualified technician.
The usual causes, and what you can check
| Cause | What you will notice | Safe owner check |
|---|---|---|
| Season, fog, smog, cloud | Output low across the whole area, worse in winter | Compare with the same month last year |
| Dust and bird droppings | Slow decline over weeks, recovers after cleaning | Look at the panels from a safe spot |
| New shade (tree growth, new building, water tank) | Drop at certain hours only | Watch the roof at morning and afternoon |
| Heat in summer | Midday output lower than spring on hot days | Normal within limits; see our heat guide |
| Export limit or zero export | Output flattens at midday when the house uses little | Compare generation curve on busy vs quiet days |
| Battery full (hybrid) | Output drops once battery reaches 100% | Check battery SOC at the time of the drop |
| Inverter overheating or derating | Output flat-tops or falls in the afternoon | Check inverter temperature and alarms in the app |
| String or input not working | One PV input shows zero or far lower than the other | Compare PV1 and PV2 in the app |
| Tripped DC breaker or isolator | Total or partial loss of generation | Look at breaker positions; do not reset repeatedly |
| Monitoring error | App shows zero but meter or inverter screen shows output | Check the inverter display |
1. Dust and dirt
Punjab dust, smog residue and bird droppings build up quickly, especially in dry months and near roads or factories. A gradual drop that recovers after a wash is the classic sign. Our solar panel cleaning guide covers how often to clean and how to do it without damaging the glass.
2. Shade that was not there before
Trees grow, neighbours build, and new water tanks or dish antennas appear. In winter the sun is lower, so shadows are longer. A drop at the same hours every day points to shade. Because panels are wired in strings, a small shadow can cost more output than you would expect; see how shading cuts solar output.
3. Summer heat
Panels lose some output as they get hotter, so a very hot June afternoon can give less than a cool, clear March day. This is normal and is covered in our guide to solar panels in Punjab summer heat.
4. The inverter is holding output back
This is the most common cause we see that owners do not expect. An inverter only produces what it can use, store or export.
- Export limit or zero export. If your system has no net billing agreement, or the export is capped, the inverter reduces output once the house load is met. On a quiet day the panels are capable of more than you see. Our zero export device guide explains how this works.
- Battery full. On a hybrid system, once the battery is full and the loads are met, output falls back to match demand.
- Clipping. If the panel capacity is larger than the inverter's AC rating, output flattens at the inverter's limit around midday. This is often a deliberate design choice, explained in our inverter DC/AC ratio guide.
- Heat derating. An inverter in direct sun or a closed room protects itself by cutting output. See inverter overheating in summer.
A flat line at midday in the app, rather than a smooth curve, usually means one of these.
5. A fault in the system
Some drops point to a real fault:
- One PV input reads zero or very low while the other is normal. A string may be disconnected, a connector may have failed, or a DC breaker may have tripped.
- Generation stops completely on a sunny day with the grid present.
- Repeated isolation or earth fault alarms, often after rain.
- A visible problem on a panel, such as cracked glass, brown marks or a burnt junction box. See hot spots, cracks and snail trails on solar panels.
Our solar inverter faults guide explains common alarm messages, and solar breaker keeps tripping covers breaker causes.
6. The app is wrong, not the system
If the app shows zero but the inverter screen shows power, the problem is usually Wi-Fi or the dongle. See solar monitoring app offline or showing zero.
A step-by-step check for owners
- Note the pattern. Is the drop every day, only at certain hours, only after rain, or only on low-load days?
- Read the inverter screen. Check for alarms and confirm it shows generation.
- Open the app's daily curve. A smooth bell shape with a dip suggests shade or cloud; a flat top suggests a limit; a sudden cut suggests a trip.
- Compare the PV inputs. If your inverter has two or more inputs, they should usually be similar when the strings are similar.
- Look at the panels from a safe place. Check for dust, droppings, leaves and new shade.
- Check the breakers by eye. Note any tripped breaker; reset only by the manual's sequence, and only once.
- Record what you found. Photos of the screen, the app curve and the breakers help a technician diagnose faster.
Our solar monitoring app guide shows where to find these readings on common apps.
Simple example arithmetic
Say a system is expected to make, for example, about 4 units per kW per day in a good month, and it is 10 kW. That is roughly 40 units a day. If your app shows 38, that is within normal day-to-day variation. If it shows 25 on a clear day with clean panels, that gap is worth investigating. These are round illustrative numbers, not a promise of what any system will produce.
For a structured comparison after twelve months, see our year one review guide.
When to call a technician
- One string or input reads zero.
- A breaker or isolator trips again after one reset.
- The same fault alarm keeps returning.
- Output is far below the same month last year on clear days, with clean panels and no new shade.
- You see damage, burn marks or melted parts.
Regular inspection catches most of these early. Our annual solar maintenance checklist lists what to check and when.
How Solar Works handles low-output complaints
For systems we install, after-sales complaints are handled by Solar Works Pakistan's own engineering and technical staff. Once a complaint is registered, we target sending service personnel within 48 hours to begin diagnosis. That is a target to start work, not a fix time; repair time depends on the fault, parts and manufacturer involvement. Our 1-year service warranty applies under the applicable project terms, and after the first year service is chargeable. Panel and inverter defects go through the manufacturer's warranty. Find out more on our solar installation services page.
We can also inspect and diagnose systems installed by other companies, as a chargeable service, across Punjab.
Get today's price or a free site survey
Worried your system is under-performing, or planning a new one? Send us a screenshot of your app's monthly generation and a photo of the inverter screen.
- WhatsApp or call: 0336 666 4321
- Email: info@solarworks.pk
- Head office: Main Boulevard, Sargodha Rd, Block F FDA City, Faisalabad
- Lahore branch: 2nd Floor, Jeff Heights, Gulberg, Lahore
- Hours: 9:00 AM to 6:00 PM, daily
We serve customers throughout Punjab. See our Faisalabad and Lahore pages, or contact us. Site surveys for new systems are normally free.
Frequently asked questions
Why is my solar system producing less in winter?
The sun is lower, days are shorter, and fog and smog cut the light reaching the panels. Shadows from tanks and walls are also longer. A winter drop is normal; compare with the same month last year instead of with spring.
Why does my solar output go flat at midday?
A flat top on the daily curve usually means the inverter is limiting output: an export limit, a full battery, clipping at the inverter's rating, or heat derating. Check the app at that time to see which applies.
Can dust really reduce solar output much?
Yes. In dusty Punjab conditions, a dirty panel can lose a noticeable share of its output, and bird droppings act like small fixed shadows. If output recovers after cleaning, dust was the cause.
One input on my inverter shows zero. What should I do?
Do not touch the DC wiring. Note the reading, check whether a DC breaker has tripped, and call your installer. A string at zero needs a technician with the right test equipment.
Do solar panels lose output as they age?
Yes, slowly. All panels degrade a little each year, at a rate given in the manufacturer's datasheet and warranty. Ageing causes a gradual decline, not a sudden drop.
Can Solar Works guarantee how many units my system will make?
No. Nobody controls the weather, so no honest company can guarantee generation. We give site-specific estimates with the assumptions shown, and we investigate when output falls below what the site should deliver.