Solar Payback Period in Australia — Calculation Guide

What Is Payback Period?

Payback period is how long it takes for your solar system to generate enough electricity value to equal its upfront cost.

Example: $5,500 system that saves $1,500/year = 3.7 year payback.

After payback, electricity is essentially free (minus inflation). So payback is the critical number.

The Payback Formula

Payback (years) = System cost ÷ Annual savings

Annual savings = (Self-consumption × consumption rate) + (Exported power × feed-in rate)

Let's break this down.

Step-by-Step Calculation

Step 1: Get your annual consumption (kWh).

• Look at your last 12 months of electricity bills
• Total kWh used
• Example: 8,000 kWh/year

Step 2: Estimate solar generation.

• Use PVGIS (European solar calculator): pvgis.solargis.com
• Enter your postcode/address
• It calculates annual generation for a given system size
• Example: 6.6kW system in Sydney generates 7,500 kWh/year

Step 3: Estimate self-consumption %.

• This is the % of solar generation you use on-site (vs export)
• Varies based on consumption habits
• Default assumption: 70% for households (people are home during sunny hours)
• Conservative assumption: 60%
• Example: 7,500 kWh × 70% = 5,250 kWh self-consumed

Step 4: Calculate consumption savings.

• Self-consumed kWh × electricity consumption rate
• Example: 5,250 kWh × $0.35/kWh = $1,838/year

Step 5: Calculate export credit.

• Exported kWh × feed-in tariff
• Example: (7,500 - 5,250) × $0.08/kWh = 2,250 × $0.08 = $180/year

Step 6: Total annual savings.

• Consumption savings + export credit
• Example: $1,838 + $180 = $2,018/year

Step 7: Calculate payback.

• System cost ÷ annual savings
• Example: $5,500 ÷ $2,018 = 2.73 years

This system pays for itself in 2.7 years.

Worked Examples by City

Sydney, NSW

Assumptions:

• 6.6kW system cost: $5,500 (after STC)
• Annual generation: 7,500 kWh (Sydney averages)
• Consumption rate: $0.35/kWh
• Feed-in rate: 8c/kWh
• Self-consumption: 70%

Calculation:

• Self-consumed: 7,500 × 70% = 5,250 kWh
• Consumption savings: 5,250 × $0.35 = $1,838
• Exported: 7,500 × 30% = 2,250 kWh
• Export credit: 2,250 × $0.08 = $180
• Total savings: $2,018
• Payback: $5,500 ÷ $2,018 = 2.7 years

Brisbane, QLD

Assumptions:

• 6.6kW system cost: $5,000 (after STC, competitive market)
• Annual generation: 8,000 kWh (Brisbane excellent irradiance)
• Consumption rate: $0.36/kWh
• Feed-in rate: 9c/kWh
• Self-consumption: 75% (warmer climate, more home occupancy)

Calculation:

• Self-consumed: 8,000 × 75% = 6,000 kWh
• Savings: 6,000 × $0.36 = $2,160
• Exported: 8,000 × 25% = 2,000 kWh
• Credit: 2,000 × $0.09 = $180
• Total: $2,340
• Payback: $5,000 ÷ $2,340 = 2.1 years

Melbourne, VIC

Assumptions:

• 6.6kW system cost: $4,800 (after STC + Victoria Solar Homes $1,400)
• Annual generation: 6,500 kWh (Melbourne lower irradiance)
• Consumption rate: $0.34/kWh
• Feed-in rate: 7c/kWh
• Self-consumption: 65% (cloudy climate, less sunny hours)

Calculation:

• Self-consumed: 6,500 × 65% = 4,225 kWh
• Savings: 4,225 × $0.34 = $1,437
• Exported: 6,500 × 35% = 2,275 kWh
• Credit: 2,275 × $0.07 = $159
• Total: $1,596
• Payback: $4,800 ÷ $1,596 = 3.0 years

Perth, WA

Assumptions:

• 6.6kW system cost: $5,500 (less competitive market)
• Annual generation: 7,000 kWh (excellent irradiance)
• Consumption rate: $0.35/kWh
• Feed-in rate: 8c/kWh (DEBS stable rate)
• Self-consumption: 70%

Calculation:

• Self-consumed: 7,000 × 70% = 4,900 kWh
• Savings: 4,900 × $0.35 = $1,715
• Exported: 7,000 × 30% = 2,100 kWh
• Credit: 2,100 × $0.08 = $168
• Total: $1,883
• Payback: $5,500 ÷ $1,883 = 2.9 years

Hobart, TAS

Assumptions:

• 6.6kW system cost: $5,500
• Annual generation: 4,800 kWh (Tasmania lowest in Australia)
• Consumption rate: $0.32/kWh
• Feed-in rate: 6c/kWh
• Self-consumption: 65% (cloudy, lower self-consumption potential)

Calculation:

• Self-consumed: 4,800 × 65% = 3,120 kWh
• Savings: 3,120 × $0.32 = $998
• Exported: 4,800 × 35% = 1,680 kWh
• Credit: 1,680 × $0.06 = $101
• Total: $1,099
• Payback: $5,500 ÷ $1,099 = 5.0 years

Variables That Affect Payback

System cost: Higher cost = longer payback. Shopping around matters.

Electricity rate: Higher rate = faster payback. If you pay $0.40/kWh, payback is shorter than $0.30/kWh.

Feed-in rate: Lower rate = slightly longer payback (but affects only 20–30% of savings).

Solar generation: Higher generation (better location) = faster payback. Shade reduces generation significantly.

Self-consumption: Higher self-consumption = faster payback. Running appliances during sunny hours helps.

Sensitivity Analysis: What If Assumptions Change?

Electricity rate increases 10%:

• From $0.35 to $0.385/kWh
• Savings increase proportionally
• Payback improves (shorter)
• Example: Sydney payback improves from 2.7 to 2.5 years

Feed-in rate drops 50% (from 8c to 4c/kWh):

• Exported credit is cut in half
• Total savings drop by 10% (since exported power is only 25–30% of benefit)
• Payback worsens slightly
• Example: Sydney payback increases from 2.7 to 2.9 years

Generation is 20% lower (shade, poor orientation):

• All savings drop proportionally
• Payback extends significantly
• Example: Sydney payback extends from 2.7 to 3.4 years

This is why shading analysis is important. Shade reduces generation, which tanks payback.

Add-Ons That Affect Payback

Battery (+$8k after rebate):

• Solar payback: 2.7 years
• Battery payback: 10+ years (weak)
• Combined payback: 5.5–6 years
• Wait a few years before adding battery

VPP payment (+$700/year in NSW/SA):

• Accelerates payback by 1 year
• Makes battery more attractive

State rebates:

• Victoria $1,400: Reduces upfront cost, accelerates payback by 0.5 years
• NSW interest-free loan: De-risks payback (no interest accrual)

Conservative vs Optimistic Assumptions

Conservative payback (accounts for variations):

• Use 60% self-consumption (not 70%)
• Use lower feed-in rate (5–6c/kWh)
• Use lower irradiance estimate
• Assume system output drops 10% (soiling, degradation)

Result: 5–7 year payback (safer estimate)

Optimistic payback (best case):

• Use 80% self-consumption
• Use high feed-in rate (10c/kWh)
• Use high irradiance
• Assume peak output

Result: 2–3 year payback (best case)

Honest estimate: 3–5 years for most Australians.

After Payback

Once payback is achieved, solar generates nearly free electricity:

Year 6+:

• Annual savings: same as year 1 ($2,000/year, with inflation)
• No more debt/cost
• Pure profit
• 25-year system lifespan: 20 years × $2,000 = $40,000 pure profit

The Bottom Line

Australian solar payback is 3–5 years for most people. This is excellent compared to almost any other investment.

Once payback happens, you're profiting for 20+ years. This is why solar is worth it for almost every Australian homeowner.

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• Is Solar Worth It in Australia 2026?
• Solar Panel Cost in Australia 2026