Solar panels are a set and forget investment for most homeowners. You get the install, watch your power bill decrease over time, and don't think much about it again. And that's where the problem begins to arise.
Panels degrade gradually. Dust settles, pollen coats the glass, bird droppings create localised hot spots. None of it triggers an alarm. Your system keeps generating, just less and less, quietly month after month. By the time the loss is reflected on your bill, you've already handed back hundreds of dollars in output you paid for when you bought the system.
Why NZ panels get dirty faster than you'd expect
New Zealand's climate is often assumed to be clean and rainy, panels should wash themselves, right? Not quite. Rainfall deposits a residue film as water evaporates, especially in urban areas with traffic pollution or coastal zones with salt spray. In many cases, light rain makes soiling worse, not better.
"Rain alone won't clean panels effectively, it just moves the dirt around. The only way to know your system is running clean is to measure what it's actually producing versus what it should be."
— SolarPal, after 6 consecutive elevated PM10 days in AucklandWhat the output gap actually costs
The financial impact of soiling depends on your system size, your local electricity rate, and how long panels have been dirty. Here's a conservative estimate for a 5kW system in the Auckland region:
That's a clear return but most homeowners never see it because there's no before and after measurement. SolCare tracks your output gap in real time, so SolarPal can tell you not just that a clean is due, but exactly what it's worth before you book it.
The hot spot problem and why it matters long-term
There's a secondary cost to dirty panels that many solar owners never factor in: Panel Degradation. When part of a panel's surface is shaded whether by a bird dropping, a patch of pollen, or a build up of debris, the unshaded cells try to push current through the shaded ones. This creates localised overheating, known as a hot spot.
Hot spots accelerate the degradation of solar cells permanently. A panel that degrades faster means a shorter effective lifespan and solar panel replacements can be costly. Majority of New Zealand solar installers ensure a 25-30 year panel lifespan under normal manufacture warranty conditions. Persistent soiling can meaningfully shorten that.
How often should New Zealand solar owners clean their panels?
The honest answer: it depends on where you live and what your data shows. A blanket schedule misses the point, a system in Remuera surrounded by pōhutukawa trees needs more attention than a system on open farmland in the Waikato.
SolarPal tracks this dynamically using your real generation data, live PM10 readings, and Solcast irradiance forecasts. But if you're working without monitoring, here's a rough guide by NZ context:
How SolarPal handles this for you
SolCare connects directly to your inverter and cross references your actual generation against what Solcast forecasts you should be producing for that day's irradiance, temperature, and cloud cover. When there's a persistent gap that weather doesn't explain, that's soiling.
SolarPal also monitors PM10 air quality in your region in real time. When particulate levels have been elevated for several days and your output gap is widening, it notifies you directly, not with a generic alert but with the specific dollar value of what you're losing and a suggested clean window based on upcoming weather.
You pick a time. SolCare dispatches a vetted local cleaner. After the job, SolarPal sends you a before and after performance report so you can see exactly what the clean recovered. The whole thing takes one tap to book and nothing else from you.
See what your panels are actually doing
Connect your inverter and SolarPal starts monitoring immediately. Most users see their first insight within 24 hours.
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