Solar Panels

Solar Panel Costs and STC Rebates

The federal government’s Small-scale Technology Certificates scheme is the primary mechanism that reduces the upfront cost of solar in Australia. When a CEC-accredited installer commissions a system, they assign the STCs to a registered agent in exchange for a point-of-sale discount — you never see the certificates, just the reduced price.

The number of STCs a system earns depends on three variables: your STC zone (1–4, with 1 being the highest solar resource), the system’s capacity in kW, and the number of full calendar years remaining until the scheme ends on 31 December 2030. A 6.6kW system in Zone 3 — covering most of NSW, VIC, SA, and parts of WA — earns approximately 85–95 STCs in 2026. At the current STC market price of around $35–$38, that translates to a rebate of $2,975–$3,610 off the installed price before any mark-up or margin adjustments by the installer.

The STC price is not fixed. It fluctuates with supply and demand in the open market. Prices have been relatively stable in the $35–$40 range in recent years, but installers typically use a forward contract price. The rebate you see quoted already reflects what your installer expects to receive — you don’t take on price risk.

Beyond the STC, installed cost is driven by:

• Panel quality and efficiency. Budget Tier 1 panels (LONGi, Risen, Astronergy) cost less per watt than premium options (REC Alpha, Jinko Tiger Neo, SunPower Maxeon). The performance difference is modest for most residential applications, but premium panels generally carry longer product and performance warranties.
• Inverter choice. String inverters (Fronius, SMA, SolarEdge, Sungrow) are the standard. Microinverters (Enphase) cost more but offer panel-level monitoring and better performance under partial shading. Sungrow and Fronius are the most common inverter brands installed in Australia and have strong local support.
• Roof complexity and cable run. A single-pitch north-facing roof with a short cable run to the switchboard costs less to install than a complex multi-pitch roof or a long run from rooftop to meter board. Tile roofs require tile hooks and additional labour; metal roofs are generally faster to work with.

A budget 6.6kW system — Tier 1 Chinese panels, Sungrow inverter, standard roof — typically lands at $5,000–$6,500 after STCs. A premium system with REC or Jinko Tiger Neo panels and a Fronius or SolarEdge inverter sits at $7,500–$9,500 for the same capacity.

Payback Period and Self-Consumption

The payback period calculation comes down to how much of your solar generation you actually use yourself versus how much you export.

Feed-in tariffs (FiTs) across most of Australia have fallen sharply over the past five years. Most retailers in NSW, VIC, SA, and QLD now offer FiTs of 3–10c/kWh for exported solar. The days of 44–60c FiTs that made export valuable are long gone in most states. This fundamentally changes the solar value proposition: exported solar earns 3–10 cents per kWh; solar consumed directly offsets grid electricity you’d otherwise buy at 28–35c/kWh. Self-consumption is worth three to ten times more per kWh than export.

For a household that is largely empty during the day — both adults at work, no EVs or appliances running — self-consumption rates may be as low as 20–30%. The bulk of generation gets exported at low FiT rates, and the payback period extends toward the longer end of the 5–8 year range.

Load shifting changes the picture significantly. Strategies that move consumption into solar generation hours (roughly 9am–3pm on sunny days):

• EV charging. Schedule the car to charge during the day, either via the car’s built-in timer or a solar-divert charger. A 7kW charger running for 3 hours consumes 21kWh — more than many household systems generate in a day, but it absorbs surplus that would otherwise be exported.
• Heat pump hot water. Set the timer to run during solar hours. A heat pump drawing 600–900W for 2–3 hours consumes 1.2–2.7kWh — modest, but consistent daily offset.
• Dishwasher, washing machine, dryer. Set cycles to run at noon. Each appliance run shifts 1–2kWh into solar hours.

A household that actively load-shifts can achieve 50–70% self-consumption, compared to 25–35% with no load management. At 60% self-consumption on a 6.6kW system generating 26kWh/day (Sydney average), roughly 15.6kWh per day is self-consumed at 30c/kWh — a daily saving of $4.68, or around $1,700/year. Payback at $6,500 installed cost lands at 3.8 years.

Batteries. Adding a battery (10–13kWh at $8,000–$14,000 installed) can push self-consumption above 90% by storing midday surplus for evening use. The battery itself typically has a payback of 8–12 years on electricity savings alone, but this is narrowing as battery prices fall and grid tariffs rise. The VIC Solar Homes Battery Loan and SA Home Battery Scheme offer state-level support in some jurisdictions.

How to Size Your Solar System

The quick sizing rule: divide your average daily kWh consumption by 4 (a conservative estimate of peak sun hours that applies to most Australian capital cities) to get the system size in kW that would cover your usage.

• 15kWh/day household → 3.75kW system to cover usage
• 20kWh/day household → 5kW system
• 30kWh/day household → 7.5kW system

In practice, the minimum recommended system size for most households is 6.6kW. Panel prices have dropped to the point where adding extra capacity is relatively cheap, and more panels improve self-consumption rates and provide headroom for future load growth (EV, battery, heat pump).

A common configuration is 6.6kW of panels on a 5kW inverter. Most states and networks allow this 1.33:1 oversizing ratio. The inverter clipping that occurs at peak generation is modest and the installed cost savings of running a smaller inverter are real — Fronius and Sungrow 5kW inverters are substantially cheaper than their 6.6kW equivalents.

Roof space. Allow approximately 1.8m² per panel at standard 400W panel size. A 6.6kW system (16–17 panels) needs roughly 30m² of usable roof area, accounting for setbacks and access requirements.

Orientation and shading. A north-facing roof delivers maximum annual generation in Australia — roughly 15–20% more than the same system on an east or west face. An east/west split is a practical alternative if a north face is limited: it spreads generation across more hours of the day, which can improve self-consumption even if total generation is slightly lower. Shading from trees, aerials, or neighbouring structures has a disproportionate impact on string inverter systems — even a small shadow on one panel can reduce output across the whole string. Microinverters or DC optimisers (SolarEdge) are worth considering for heavily shaded roofs.

Choosing an Installer

Only CEC-accredited installers are eligible to assign STCs. Using a non-accredited installer means losing your rebate — which at $2,500–$3,500 represents a significant portion of the system cost. Check accreditation at the Clean Energy Council’s online register before signing anything.

Get at least three quotes. Solar quotes vary substantially — not just in price but in what is included. Compare quotes on:

• Panel model and datasheet specifications (not just brand name — confirm the exact model number and efficiency rating)
• Inverter brand and model (confirm the warranty period and whether the manufacturer has a local support presence in Australia)
• Warranty terms — panel product warranty (10–12 years is standard, 25 years for SunPower), panel performance warranty (90% at 10 years, 80–82% at 25–30 years is typical), and workmanship warranty (minimum 5 years, 10 years for reputable installers)
• Monitoring app — most modern inverters include Wi-Fi monitoring; confirm the app is included and what it tracks (system generation, household consumption, and export)
• Payment terms — be cautious of large deposits. Reputable installers typically take 10–20% upfront and the balance on completion.

Ask each installer how long they have been in business and whether they use subcontractors. Many solar companies use third-party installation crews — not inherently a problem, but worth knowing who will be on your roof and who to call if there’s an issue post-installation.