How fast does solar pay itself off in Adelaide?

Three Adelaide household profiles (all post-rebate, May 2026 numbers):

Profile A - Light user (couple, retiree)

• 12 kWh/day use, 6.6kW solar at $6,500 installed
• Self-consumption: ~35% (most use is morning + evening)
• Annual saving: ~$1,400
• Payback: ~4.6 years

Profile B - Average family (4 person, ducted aircon)

• 22 kWh/day use, 6.6kW solar at $6,800 installed
• Self-consumption: ~45%
• Annual saving: ~$1,700
• Payback: ~4.0 years

Profile C - Heavy user (5 person, pool, EV)

• 35 kWh/day use, 10kW solar at $11,000 installed
• Self-consumption: ~55%
• Annual saving: ~$2,800
• Payback: ~3.9 years

All figures assume a grid tariff of $0.42/kWh and feed-in of $0.06/kWh.

Adding a battery lengthens payback but increases total lifetime savings.

Profile B with 10kWh battery (post federal rebate ~$3,110 off):

• 6.6kW solar + 10kWh battery at $17,500 installed
• Self-consumption: ~85% (battery captures evening use)
• Annual saving: ~$2,400
• Payback: ~7.3 years
• Lifetime savings (25 years): ~$60,000 (vs $43,000 solar-only)

The battery accelerates lifetime savings even though it slows immediate payback.

Variables in order of impact:

1. Self-consumption rate - the single biggest lever. Shifting load to daytime (pool pump, dishwasher, washing, hot water boost) can lift self-consumption from 35% to 60%, dropping payback by 1-2 years.
2. Grid electricity rate - higher peak rates = faster payback. SA's high tariff is why Adelaide payback beats Brisbane and Perth.
3. System size relative to consumption - oversized systems export more, payback slower. Right-sizing matters.
4. Feed-in tariff - matters less than it used to. A 4c gap in feed-in tariff costs about $200/year.
5. Install cost - bargain systems can pay back faster on day-1 maths but cost more in repairs / replacements.