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Intelligent Solar Roof puts an end to power bills

7 May, 2014

Intelligent Solar Roof puts an end to power bills

The country’s first Zero Energy House has used solar to generate double the electricity it needed over a year, earning the owners a net income [1] for electricity bills.

In 2012, SolarCity supplied the home’s owners Joanna Woods and Shay Brazier with an Intelligent Roof deploying both a photovoltaic and a solar hot water system on their Point Chevalier-based Zero Energy House (ZEH). The home aimed to achieve net-zero energy by generating as much electricity as it consumed, through a blend of energy-efficient features and an Intelligent Solar Roof. Results released today show it exceeded expectations with the award of the international living futures’ certification.

“Two years ago Shay and Jo set out to see if they could build a zero energy house,” says Andrew Booth, CEO of SolarCity. “The home’s performance and energy use was tracked in detail, and over 12 months their solar power system generated more than double the electricity required by the home and delivered a net income to the family of $360 at the end of that year.”

As the price of power continues to rise and the price of solar continues to fall Shay and Jo’s home shows a way forward for the nation’s families.

“Our Zero Energy House protects us from the impact of electricity rate increases while safeguarding the environment,” Shay Brazier says. “The country needs to start thinking about making their roofs more intelligent, and about the cost of running a house per square metre, rather than just the cost of building a house per square metre.

“An Intelligent Roof works for you, rather than sits dormant,” he says. “It uses the free sunshine and turns it into electricity, which can be a huge monthly cost for everyone. There are systems available today that, on a house with this energy profile and feed-in tariff, cost substantially less than the value they would generate over the home’s lifetime.”

To build on the success of the Zero Energy Home, SolarCity is working alongside developers like Maxim in Christchurch, who are building the nation’s largest solar sub-division with 2,200 homes being equipped with solar as standard. Nationally, leading homebuilders Jennian are already pre-wiring homes for solar.

“Our Jennian homes are already ‘solarsmart’ and are pre-wired for solar photovoltaic systems,” says Richard Carver, CEO of Jennian Homes. “Net-zero homes are an important next step to help protect owners from the impact of rising electricity costs while safeguarding the environment for the next generation.”

[1] Net income for electricity bills is calculated by subtracting the payments made to the ZEH owners for exported electricity, less the payments they made to the retailer for imported electricity. It does not include the cost of repayment of the solar system or consider the benefit relative to a house with the same energy usage profile, but without a PV system installed.

Zero Energy House Results
• Amount generated 5,400 kWh.
• Amount used 2,400 kWh.

Economic case for PV system
Economics of PV are based on the value the system generates, and what it costs.

Value is calculated by adding the savings it provided on the electricity bill to the income generated by selling surplus electricity.
• If the PV hadn’t been on the roof the house would have cost $610 to run (based on importing all 2,400 kWh).
• The actual bill was $390. The savings the system provided were then $610 - $390 = $220.
• The income generated by selling surplus electricity was $750. $750 - $390 = $360 profit.
• Total system value was therefore $220 + $750 = $970.

A standard system of the size installed at the ZEH could be purchased for $12,500. Added onto a 25-year mortgage at 6%, annual cost would be ~$970.

Key inputs:
• Fixed daily charge $ 0.259974/day (after prompt payment discount)
• Variable charge $0.218665/kWh (after prompt payment discount)
• Prompt payment discount 22%
• Feed-in tariff $0.17285/kWh
• Amount generated 5,387 kWh.
• Amount used 2,361 kWh.
• Imported 1348 kWh.
• Exported 4341 kWh.

For more go to:

About SolarCity
SolarCity is the nation's leading solar power company. It is also one of the top five fastest growing Green companies in New Zealand, and is one of the Government’s Focus 500 companies targeted to contribute significant benefits to the New Zealand economy. It is the world’s first solar company to achieve CarboNZero accreditation and is under contract to install 3.4Mw of solar on the nation’s largest solar sub-division.


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