Solar Calculation Tool — Rooftop Solar Plan (Hydro vs PV, month by month)

Solar Calculation Tool

Replacing lake drawdown with rooftop PV Fully editable, month by month

Total Kiwi investment (to date)$0capex committed by households

Hydro energy offset (cum.)0 GWh0% of target • avoided drawdown 0.00 m

Participants & PV capacity0 homes0.0 MW total @ 10 kW/home

Global assumptions

Lake area A (km²)

Combined net head H (m)

Hydro efficiency η

Target drawdown Δh (m)

Program horizon (months)

Timeframe for hydro comparison (days)

PV system per home (kW)

Annual PV degradation (%/yr)

Cost per kW (NZD/kW)

Fixed BOS/other (NZD)

O&M (% of capex/year)

Share financed (%)

Loan interest p.a. (%)

Loan term (months)

Deposit (% of capex)

Assume mid-month install

Retail price (c/kWh)

Default buy-back (c/kWh)

Self-consumption (%)

Curtailment loss (%)

Notes:

• Hāwea area 149 km²; Clyde 60 m; Roxburgh 40 m.

• MBIE QSDEP retail: Queenstown ~39.5 c/kWh.

• Export limits: Aurora 10 kW (Aug 2025).