| 12.12kW Solar Array | 13.5kWh Tesla Powerwall 3 | 63% Bill Reduction | $4,396 Year 1 Savings |
Project Overview
Solar battery storage NZ systems make the biggest difference for households with big power bills, and this Waitati home is a clear example. Using around 50kWh a day, the household was facing an annual electricity bill of about $6,920. Future Energy designed a 12.12kW solar array using 24 Suntech Ultra V Pro panels, paired with a Tesla Powerwall 3 home battery, projected to cut that bill to roughly $2,530. That is a 63% reduction, with $4,396 saved in year one and lifetime savings estimated at $116,253 over 25 years.
The Challenge
At around 50kWh a day, this household uses several times the electricity of a typical home, and at a flat rate of 35c per kWh, every unit bought from the grid adds up fast. Solar alone would offset the daytime load, but a large share of this household’s use falls in the evening and overnight, when panels produce nothing. The challenge was to capture as much of the solar generated as possible and carry it into the hours when the home uses the most power, rather than exporting it at a much lower rate.
The System
24 Suntech Ultra V Pro Panels at 12.12kW
The system uses 24 Suntech Ultra V Pro mini STP505S panels for a combined array output of 12.12kW, split evenly across two north west facing roof sections of 12 panels each at a 23 degree tilt. The array is expected to generate around 15,081kWh a year, or about 41kWh a day, with estimated shading losses of just 1.5%.
Tesla Powerwall 3 With 10kW Inverter
A Tesla Powerwall 3 combines a 10kW solar inverter and 13.5kWh of battery storage in a single unit. It stores surplus solar generated during the day and releases it in the evening and overnight, and can be monitored and managed through the Tesla app. The unit carries a 10 year warranty.
Solar That Stays On Site
Modelling shows 48.1% of the solar generated is used directly in the home, a further 25.2% is stored in the battery for later, and only 26.7% is exported. Overall, 60% of the household’s energy use is self consumed, and what is exported still earns an estimated $617 a year in export credits.
The Results
- 12.12kW solar array with a Tesla Powerwall 3 and 13.5kWh of battery storage
- Annual power bill projected to fall from around $6,920 to roughly $2,530, a 63% reduction
- Year 1 savings of $4,396, made up of $3,780 in grid energy savings plus $617 in export credits
- 60% of the household’s energy use self consumed, with only 26.7% of generation exported
- Estimated lifetime savings of $116,253 and a payback period of 7 years and 5 months
- A 14.05% internal rate of return, a net present value of $66,102 and 1.9 tonnes of CO2 avoided each year
Big power bills, cut down to size.
Frequently Asked Questions
Is a home battery worth it for a household with high power bills?
Often, yes. The more electricity a home uses in the evening and overnight, the more value a battery adds, because stored solar replaces grid power bought at the full retail rate. For this Waitati home using around 50kWh a day, adding a Powerwall 3 lifted self consumption to 60% and is projected to cut the annual bill by 63%.
What is a Tesla Powerwall 3?
The Powerwall 3 is an all in one home battery and solar inverter. It stores 13.5kWh of energy, supports up to 20kW of solar input and delivers up to 11.04kW of continuous power. It can be managed through the Tesla app and carries a 10 year warranty.
How long does a solar and battery system take to pay for itself?
This Waitati system is projected to pay for itself in 7 years and 5 months, based on year one savings of $4,396. Over 25 years, estimated savings reach $116,253, with a 14.05% internal rate of return.
Can solar panels all face one direction?
Yes. This installation places all 24 panels on two north west facing roof sections at a 23 degree tilt, with shading losses estimated at only 1.5%. Future Energy models each roof surface to confirm the expected output before recommending a system.
Facing large power bills? Future Energy designs solar battery storage NZ systems sized to your real consumption, so you can see the savings before you commit. Get in touch for a free assessment.
