Solar payback basics (New Zealand)
A practical overview of how rooftop solar “pays back” — and how bill tracking helps you sense-check quotes.
Installers often quote a payback period: years until savings roughly equal what you spent on panels, inverter, and install. It’s a useful conversation starter, not a guarantee.
What “payback” usually means
Roughly:
System cost ÷ annual bill savings ≈ years to payback
Savings come from:
- Self-consumption — power you generate and use instantly (avoids buying from the retailer)
- Export credits — payment or bill credit for unused generation sent to the grid (rates vary by retailer and plan)
What changes the number
- Your usage pattern — home during the day? Heat pump / EV? Self-consumption rises.
- Roof and location — orientation, shade, and regional sun hours
- Retail plan — daytime rates, controlled hot water, and export buy-back
- System size & price — bigger isn’t always faster payback
- Battery — can increase self-use but adds cost and complexity
Why tracking bills helps
Before you trust a spreadsheet from a sales visit, know your last 12 months of kWh and $. That’s what My Energy Tracker is for: a clean history you can compare against a quote’s assumptions.
After install, keep logging bills so you can see whether export and usage match what you were told — and catch plan changes that quietly move the goalposts.
Sensible next steps
- Log several months of bills (or a full year if you have them).
- Note day/night or controlled loads if your bill splits them.
- Get more than one quote; ask each for assumed self-consumption % and export rate.
- Treat payback as a range, not a single magic year.
Start with your power bill My Energy Tracker home
How to read a power bill · This is general information, not financial or install advice.