Solar Calculator | Watt Works | Tauranga, New Zealand

1What size system??Find the kWh you used over the last year on your power bill. In the Bay of Plenty every 1 kW of panels makes roughly 1,300 kWh a year, so an 8 kW system generates about 10,000 kWh. Bigger is not always better, you only save on what you use during the day or store in a battery. A typical Bay of Plenty home lands somewhere between 5 kW and 10 kW. We check it properly during the site visit.

Not sure? Start at 6 kW. We can help size it properly against your power bill before you commit. Click the Question mark for more info

8.1kW

17 × 475 W panels

2.9 kW14.3 kW

Power supply at the property

Single phase Most homes Three phase Systems to 45 kW

Not sure? We can confirm in a site visit. Or look at your switchboard: three phase has three main fuses or a wider main switch, often labelled 400V.

2 Roof pitch

Steeper roofs need more fall protection and take longer to work on.

Flat Under 10° Medium 10–25° Steep Over 25°

3 Roof type and height

Tile roofs need special brackets compared to the simpler tin brackets, and every extra storey adds access gear.

Iron Corrugated steel Tile Concrete or Metal

Single storey Two storey Three storey +

4 Where is the property?

We install right across the Bay of Plenty and Waikato. Anywhere outside Tauranga carries a small travel allowance.

5 Battery

Three ways to go. Grid-tied is the simplest and cuts your daytime bill. Battery ready puts the hybrid inverter and groundwork in now so a battery can be added whenever you are ready. Battery included gives you storage and backup power from day one.

Grid-Tied Sungrow grid-tied inverter with WiFi monitoring. The most direct way to cut your daytime power bill. When the sun's out, you're saving! Battery ready Sigenergy hybrid energy controller and floor stand installed, and space provisioned for a future battery when required. Makes sure you don’t double pay down the track if you decide you want a battery. Battery included Everything in battery ready, plus a SigenStor battery and Sigen Gateway for backup power. That means power to help offset your peak cost hours, and if the power is out you can still keep the house running.

Prices are indicative only and assume a standard cable run and a switchboard with spare capacity. They are not a formal offer. We confirm the final figure after a site visit, but we always aim to be close with the calculator. The drawing is a sketch of the system you have chosen, not a plan of your own roof. Generation and savings figures are explained further down the page.

The long game

What This System Saves You

For the 8.1 kW grid-tied system you have configured, starting from today’s power prices, we have done the work to give you a first indication of what the savings might be for the selected system over its life.

How much power do you use?

We have started with a typical Bay of Plenty home. Put your own figures in and everything below updates. Both are on your power bill as the monthly kWh.

An average summer month kWh October to March

An average winter month kWh April to September

9,300 kWh a year.

6.4 years Until it has paid for itself The point where what you have saved catches up with what you paid.

$71,400 Better off by year 25

261,000 kWh generated by year 25

25 tonnes CO₂ kept out of the grid

Where you break even

Everything you save, added up, against what the system cost you on day one.

Still paying it off
Money in your pocket

How these are worked out: we run your system month by month against the power use above. Generation is the first-year estimate for a north-facing array in the Bay of Plenty before shading, dropping 0.5% a year as the panels age. Solar first covers whatever the house is using at the time, a battery stores what is left over and gives it back in the evening, and only the remainder is exported. Rates are peak 40c and off-peak 25c in winter, peak 38c and off-peak 25c in summer, with exports paid at 32c and 18c in winter and 24c and 18c in summer. Peak is 7–11am and 5–9pm on weekdays; winter runs April to September. The daily line charge of $3 is payable with or without solar, so it makes no difference to a saving and is left out. This model was calibrated against real Watt Works proposals costed month by month from metered consumption, and lands within 2% of them on power exported, imported and saved. Assumes power prices increase at a rate of 2% per year. Carbon is at the New Zealand grid average of roughly 0.095 kg CO₂ per kWh. What you actually save still depends on your retailer, your plan and when in the day you use power, so treat this as a guide and let us check it properly against your bill. Assumes a roof mounted system.

Enquire Now

We will email this configuration through and follow up with you to book a site assessment.

What Every Install Includes

Design & Supply

475 W black bifacial Tier 1 panels, Sungrow or Sigenergy inverters, and racking specified for your roof and wind zone.

Install & Commission

Full installation by our own certified electricians, DC and AC work, isolators, labelling and system commissioning.

Compliance & Handover

Independent inspection, Certificate of Compliance, lines company application and a walkthrough of your monitoring app.

Build Your Solar Estimate