The Cathedral College

The Cathedral College

Hybrid solar central Queensland: school escapes exploding rural energy prices with Tesla battery


The Cathedral College (TCC) is a co-educational secondary catholic boarding college that is part of the Diocese of Rockhampton. The college sees itself as a regional leader in innovation offering a varied curriculum and excellent facilities which include two boarding houses and a modern campus right in the heart of Rockhampton. TCC has been operating under its current name since 1991 but prides itself on its rich history as a Central Queensland secondary school reaches back to the late 1800s. TCC was first known as the Sisters of Mercy’s Range College for girls, then as St Joseph’s Christian Brothers’ College for boys. Today, the school teaches around 1165 students, of which 180 are boarders, from years 7-12, and employs 135 teaching, boarding, and administrative staff. One of TCC’s core values is respect for the earth and all creation, which translates to a firm commitment to sustainability.

Business Problem

Apart from TCC’s wish to reduce their boarding school’s carbon footprint, the organisation has been struggling with rising electricity prices as well as increased peak demand charges, which can add a substantial amount of money to commercial power bills. Just the air conditioning loads in the summer months can increase grid consumption at schools by up to 300%.

The Cathedral College, along with other Catholic schools across the country, also wish to reduce their environmental impact by becoming a solar high school and producing the bulk of the energy they use on-site.

 Financial Data:

Total project cost of AU$285,000

Payback period of six years

Cash-flow positive in the first quarter

50% total reduction in kWh consumption from the grid

Annual carbon offset of 40 tonnes


System size: 85kWp 

286 x Q CELLS Q.PLUS BFR-G4.1 280W solar PV panels

3 x 27.6kW commercial SolarEdge Inverters

1 x 100kWh Tesla Powerpack 1.5 Commercial Battery

The Solution

To fulfil TCC’s wish to become largely independent of the electricity grid, we first had to analyse, assess, and understand every detail of the school’s energy usage. We evaluated TCC’s consumption profile and electricity bills, inspected the site, conducted energy audits, and consulted closely with the school’s management team. Then our electrical engineering team came up with a design that included a single Tesla Powerpack commercial solar battery that would meet the bulk of TCC’s energy needs.


Because schools such as the Cathedral College operate mostly during the day, they are a perfect match for Solar PV as they will directly use up the electricity produced on the roof. At TCC, any excess production charges the Tesla Powerpack, which powers the boys’ boarding house for up to five hours once the sun goes down – for free!

The resulting reductions in both peak-time electricity usage and peak demand charges are a massive benefit to the college in regards to their cash-flow, carbon footprint, and energy independence. We were also able to optimise the Cathedral College’s supply tariff, while the hybrid solar system is designed to prevent undesirable tariff shifts in the future.

Since the solar system and battery have been commissioned in February 2017, they have exceeded all expectations, with Aaron Nunn, the Cathedral College’s ICT Manager, commenting,

“The system impresses upon our students in showing good stewardship, respecting the environment and its resources and that’s something we’re very proud of.”

On top of these excellent results in the area of economics and ecology, TCC is also using the solar PV and battery installation as a hands-on learning ground for its electrical engineering classes. In 2018 solar system design will be available as an assessment activity in the Year 10 students’ 2018 curriculum.

GEM’s general manager, Ben Kolle, commented,

‘This was one of the first Tesla Powerpack 1.5 batteries to be installed in Australia, so there was some extra work in optimising how the system performed. The roof also posed some challenges, so we opted for a SolarEdge inverter system which gave us more options for the placement of panels. We are extremely pleased with the results.’

Catholic schools have been investigating Solar PV and battery storage options for some years, and a broader rollout is underway.


The Cathedral College case is a great example of how rewarding it is for any organisation to take control of both their power generation and their consumption. In 2018, increasing your energy independence is affordable, achievable and stacked with benefits!

GEM Energy are proud to have delivered this state-of-the-art hybrid solar system for the Cathedral College in Rockhampton. We would like to take this opportunity to thank our hard-working installers out in the field, as well as TCC’s management team for putting their trust in our company.

GEM Energy are dedicated to helping Australian schools, community organisations, and businesses save money on electricity bills and gain more energy independence through our commercial solar solutions.

Get in touch for your free quote or feasibility study today!

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