The quickest way to check if your solar panels are working is to open your inverter’s monitoring app (or look at the inverter display) around midday on a clear day. If it shows power being generated, your system is working. Whether it’s working well is a separate question, and you answer it by comparing your daily output with what a system your size should produce.
Most solar problems don’t show up as a system that’s completely off. They show up as a system producing 10–20% less than it should, quietly, for months. Here’s how to check yours in about 10 minutes.
Step 1: Find Your System Size
You need one number to judge your output: your system size in kilowatts (kW). It’s usually on:
- your installation paperwork or invoice
- a sticker on the side of the inverter
- the “system info” or “site details” screen in your monitoring app
If you only know your panel count, multiply it by the panel wattage (often 370–440 W for newer panels) and divide by 1,000. For example, 16 panels × 400 W = 6.4 kW.
Note: your inverter is often smaller than your panel array, for example a 5 kW inverter with 6.6 kW of panels. That’s normal. Use the panel size for the calculations below.
Step 2: Find Your Output Numbers
There are three places to look, from most to least detailed.
1. Your monitoring app or portal. Most inverters sold in Australia come with one, such as SolarEdge, Fronius Solar.web, Enphase Enlighten, GoodWe SEMS, Sungrow iSolarCloud or Growatt ShinePhone. Look for:
- Today’s energy (kWh): the total generated so far today
- Current power (kW): what the system is producing right now
- History: daily, monthly and yearly totals
2. The inverter’s screen. If you never set up the app, most inverters show current power and the day’s total on the unit itself. Many still have an app available. Search for your inverter brand plus “app” and connect it to your Wi-Fi. It’s worth the 15 minutes.
3. Your power bill. Look for “solar export” or “feed-in” in kWh. This is only what you didn’t use at home, so it’s less reliable for checking output, but a big drop from the same quarter last year is still a useful red flag.
kW vs kWh: kW is how much power the system is producing at that moment (like a car’s speed). kWh is the total energy produced over time (like distance travelled). For checking whether your system is working well, daily kWh is the number that matters.
Step 3: Compare Against What’s Normal on the Sunshine Coast
As a rough guide, a well-performing system in South East Queensland averages about 4 kWh per day for every 1 kW of panels across the year. It’s higher on long summer days and lower in winter.
| System size (panels) | Rough daily average, sunny days* |
|---|---|
| 3 kW | 11–15 kWh |
| 5 kW | 18–25 kWh |
| 6.6 kW | 24–33 kWh |
| 10 kW | 36–50 kWh |
*Clear days only. Cloudy and rainy days will be much lower, and that’s normal. Lower end in winter, higher end in summer. Your exact figures depend on panel direction, roof pitch and shading.
Midday check: on a clear day around noon, current power is commonly 65–85% of your panel size. Panels lose some efficiency as they heat up, so a 6.6 kW system showing 4.5–5.5 kW in summer is normal. A 6.6 kW system showing 2 kW at midday in full sun is not.
Step 4: Compare Against Your Own History
Your system’s own history is a more accurate benchmark than any table. In your app:
- Open the monthly view.
- Compare this month with the same month last year. Comparing with last month will be skewed by the change of season.
- Allow for weather. A wet March will always produce less than a dry one.
A gap of about 10% or more, with similar weather, is worth looking into. If your app has a daily graph, look at the shape too. A healthy day on a clear morning is a smooth, rounded hill peaking around midday. Flat tops, sudden dips at the same time every day, or a lopsided curve can point to specific problems (see below).
Step 5: Work Out What the Numbers Are Telling You
| What you’re seeing | Likely cause | What to do |
|---|---|---|
| Zero output on a sunny day | Inverter off or faulted, isolator switched off, grid outage, or the inverter has lost Wi-Fi (app shows zero but the system is actually running) | Check the inverter screen first. If the screen shows zero or an error, contact your installer or a licensed solar electrician |
| Gradual decline over months | Dirt, salt film or droppings building up on the glass | See Signs Your Solar Panels Need Cleaning |
| Dip at the same time every day | Shade from a tree, chimney, antenna or neighbouring building at that time of day | Check the roof at that time of day. Trimming a tree can make a noticeable difference |
| Sudden drop overnight | Storm damage, a tripped isolator, or a fault in one string of panels | Get it inspected. Don’t go on the roof yourself after a storm |
| Flat top on the graph at midday | Usually your inverter hitting its maximum (called “clipping”). This is normal on oversized arrays | Nothing, if it only happens in the middle of clear days |
| App shows a gap but the bill looks fine | Monitoring dropped out (Wi-Fi changed, router replaced) | Reconnect the inverter to your Wi-Fi |
If your inverter is showing a warning light or error code, our 5-point service self-check covers what those usually mean.
What If Something Doesn’t Add Up?
If you’ve worked through the steps and your system is clearly under-producing, but the inverter shows no errors, the most common causes on the Sunshine Coast are a dirty surface (salt, pollen, droppings) or new shading, and often both.
The easiest way to find out which is a Solar Health Check. We’ll go through your output with you, record a reading before and after cleaning so you can see how much was dirt, inspect underneath and around the panels, and send you a photo report of everything we found.
FAQs
How do I know if my solar panels are working without an app?
Look at the inverter display around midday on a sunny day. It should show power being generated (in kW or W) and a running total for the day. You can also check your power bill for solar export. A sudden drop to zero suggests the system has been off.
How do I test my solar panel output myself?
For homeowners, “testing” means comparing your daily kWh with your system size (about 4 kWh per kW per day on average in SE Queensland) and with the same month last year. Electrical testing of the panels or wiring should only be done by a licensed electrician. DC solar wiring carries high voltage even when the system is switched off at the inverter.
Why are my solar panels producing less than usual?
The most common reasons are dirt or salt build-up, new shade from trees, seasonal change (winter produces less), a few cloudy days, or an inverter or wiring fault. Comparing with the same month last year rules out the seasonal effect.
Can solar panels stop working without me knowing?
Yes. Many homeowners only find out when a power bill arrives months later. If your app can send alerts, switch them on, and check your monthly total at least once a month.
How much should a 6.6 kW solar system produce per day?
On the Sunshine Coast, roughly 24–33 kWh on a clear day, depending on season, panel direction and shading. Averaged over a full year including cloudy days, about 26 kWh per day is a reasonable expectation.
Numbers not adding up? Book a Solar Health Check or get a free quote for a clean. We reply the same day with a fixed price, anywhere from Caloundra to Noosa.