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Solar ROI Calculator

Quick ROI check for solar panels and heat pumps, anywhere in New Zealand. Enter your basics and see savings, payback and next steps in 2 minutes. Free, no sign-up — everything stays in your browser.

Your Details

Enter Your Building Info

All fields have smart NZ-wide defaults — only change what applies to you.

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Building
Roof and home details for solar sizing
m²

Usable unshaded roof space — typically total footprint × 0.6 to 0.8

Optimal — North-facing maximises solar yield anywhere in NZ (100%) · 0° from north

Trees, neighbouring buildings, or chimneys casting shadow

1
Single-storey

Single-storey home. More floors = more household load = higher solar self-consumption

⚡
Energy
Current bills and heating system details
$

Check your latest 12-month electricity summary

kWh

Leave blank to estimate from annual bill ÷ $0.36/kWh

Heating & Hot Water System

COP 1.0 → heat pump saves up to 75% of heating energy

$

Your gas bill + electric heating portion. Leave blank to auto-estimate.

65% / 35%
All hot waterAll space heating

Space heating HP achieves COP 4.0 · Hot water HP achieves COP 3.5. Blended new COP: 3.83

m²

Sizes replacement HP at ~9 kW · estimated system cost $13,500

1
Single zone

Primarily used for existing heat pump systems

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Usage Pattern
Operating hours and seasonal variation

How much of the solar day (9am–5pm) is someone home? More presence = more direct solar use — self-consumption estimated at 47%

1.5×
1.0× flat year-round2.0× heavy seasonal

Peak month usage vs. monthly average. Moderate seasonal variation — typical commercial → solar self-consumption estimated at 47%

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Location
Sets regional solar yield and electricity tariff data

NIWA-estimated yield for Auckland — 1,250 kWh/kW/yr

Auckland at a Glance
Island
North Island
Grid tariff
~$0.36 / kWh
Solar yield
1,250 kWh/kW
Export credit
~$0.29 / kWh

Estimates only — actual tariffs vary by retailer and lines company.

NZ-wide regional data · No sign-up required