Commercial solar calculator: What would solar do for your power bill?
Thirty seconds to an honest, indicative answer, in the same four steps every project runs: measure, design, finance, outcome. Conservative assumptions, all disclosed below the results. The real model is built from twelve months of your bills.
Your farm or business
$
Your indicative numbers
Conservative, ex GST, modelled not promised
Measure
- Power used
- 188,235 kWh a year
- Your spend at 25.5c a kWh ex GST, the national commercial average.
- Power bill
- $48,000 a year
Design
- System
- 83 kW
- Sized to your daytime load.
- Generates
- 101,260 kWh a year
- Used on site
- 80%
- The rest exports at 8c a kWh.
- Installed cost
- $124,263 to $165,526
- Confirmed with certified installers.
Finance
- Investment Boost, year one
- about $8,114
- A 20% immediate tax deduction, worth this in cash at the 28% company rate. Not a discount.
- ASB Smart Solar Loan
- $2,415 a month
- 0% for 5 years. Reverts to a floating business rate after five years. Terms checked against asb.co.nz on 8 October 2026. ASB may change or withdraw the offer; the calculator only shows it while it matches.
- Estimated saving
- $1,684 a month
- Mid estimate, set against the repayment while the loan runs.
Outcome
- Saving
- $18,146 to $22,277 a year
- Payback
- 5.5 to 8.5 years
- Net of the Investment Boost benefit.
- Emissions avoided
- 6.0 t CO₂e a year
- Asset life
- 25+ years
- Panels keep producing long after payback.
How this is modelled (assumptions v2026-10-v7)
- Power valued at $0.20 to $0.26/kWh ex GST (savings are never valued at the top of the commercial tariff range).
- Export credited at $0.08/kWh, the conservative end of current buy-back rates.
- Installed cost interpolated from 30 kW ($1,800 to $2,600/kW) down to 500 kW ($1,100 to $1,500/kW), 2025/26 working ranges.
- Central Otago and Queenstown Lakes yield modelled at 1220 kWh per kW per year.
- Self-consumption capped by your daytime usage profile and held below typical vendor claims; sizing targets 90 percent of daytime load.
- Investment Boost stated as the year-one cash value of the 20 percent immediate deduction at the 28 percent company rate. It is a tax timing benefit, not a discount.
- No power price escalation and no panel degradation in simple payback; omitting escalation outweighs degradation, so the net effect is conservative.
Indicative only; not financial or tax advice. The feasibility study models your site from twelve months of actual bills.
Next step
Get these numbers checked properly
The real model is built from twelve months of your bills. Send your details and we will do it for you; we reply within one working day, no obligation.