Solar panels in Kings Langley

As an estimate, a 6.6kW system comes to about $3,990, a 10kW to about $5,490 and a 13.2kW to about $7,990, with the STC discount for postcode 2147 already taken off. Those are typical figures for a straightforward install, not a fixed price. Plenty of homes here already have a system from the early 2010s, in which case the real question is whether to keep, repair or replace it — and those are three quite different numbers.

Kings Langley is in STC Zone 3, rating 1.382. In 2026 a 6.6kW system creates 45 certificates, worth roughly $1,710 off the price, and a 10kW system 69 certificates, roughly $2,622. Certificates are created on new capacity, so replacing an old system with a larger one still earns them on the new installation.

Far less than the people selling maintenance plans suggest. There are no moving parts on a roof: the panels sit there, and rain does most of the cleaning. What genuinely helps is watching the monitoring, because a fault shows up as a number long before it shows up on a bill, and having the electrical side inspected periodically by an accredited electrician — isolators, connectors and mounting hardware are the parts that age. If someone is selling you an annual clean on a Sydney roof as essential, be sceptical.

Occasionally, and less often than you would think. Rain handles ordinary dust on a pitched roof. Cleaning is worth doing where something is actually accumulating — heavy bird mess, tree drop, or a very low-pitched roof that does not shed — and the way to tell is monitoring rather than looking up from the driveway. Getting on a roof is the most dangerous part of owning solar, so if it does need doing, it is not a job worth improvising on a ladder.

Start with the inverter: it should show generation during daylight and no fault codes. Then compare a week of monitoring against the same week a year earlier — a gradual decline is normal, a sudden drop is not, and a string that has stopped entirely is obvious in the data. Panels degrade slowly by design, typically a fraction of a percent a year, so a ten-year-old array should still be producing the large majority of what it did new. Inverters are the more common failure: they are electronics, and they rarely last the full life of the panels. If the numbers do not look right we will come and test it rather than guess from a description.

It depends on what has failed and how big the system is. Replacing a failed inverter on a decent-sized array is usually worth doing. Repairing a small early system — 1.5 or 2kW — often is not, because the same money spent on a modern 10kW system produces several times as much. We will tell you which case you are in, including when the answer is to leave it alone for now.

The distribution network that owns the poles and wires in your street approves it — not your retailer — and we lodge the application for you. That network also decides how much your system may export: on a flexible export connection, eligible customers can send up to 10kW per phase back to the grid most of the time, while a fixed export limit caps exports at 1.5kW. Replacing a system counts as an upgrade, so it needs a fresh application under the current rules.