The technical hurdles in achieving a NABERS and Green Star rating

There can sometimes be great difficulty for those developing new commercial or residential buildings to achieve a high NABERS or Green Star rating, including obstacles with energy efficiency and network connectivity. Finding solutions to these problems is essential.

NABERS and Green Star are Australian national rating systems that measure the sustainability and environmental performance of buildings. Both of these systems are recognized as the leading grading processes for how efficient and green a structure can be.

Making the building more energy efficient

In the commercial building world, owners can expect higher rental yields and capital growth when their buildings are more efficient and green. There are many advantages to having low carbon structures. For starters, they’re usually lower in cost to run, so tenants realise that they’ve got lower outgoing costs, making the structure more attractive to a broader audience.

Attracting tenants

Low-emission buildings are very attractive to many tenants who strive for a smaller carbon footprint or are mandated to be in buildings that have a certain Green Star or NABERS rating, for example, government departments and councils. Therefore, developing a building with lower carbon emissions makes commercial as well as environmental sense.

Co and trigeneration systems powered by microturbines are a favourite with developers who are looking to have a significant impact on their NABERS rating for a reasonable amount of capital.

The challenge is getting it right

However, the challenge before any building goes up is predicting how it will perform. In essence, no one really knows how much energy a building will use. The first step toward finding an ideal energy solution is to assess what a building’s electrical profile is going to look like.

This is a process that, while well-intentioned, doesn’t always generate the ideal outcome. Often a developer might choose a piece of on-site generation equipment based on the electrical or thermal load estimate of the structure, but in reality, the energy usage of the building is radically different.

The right tool for the job

A standard piece of co and trigeneration equipment is often restricted by the range of power it can provide. If an electrical load drops and then rises, an incorrectly sized engine will not be able to respond in time. So what happens when the predicted electrical demand of a structure just isn’t there?

In this instance, often the engine is incapable of providing the lower electrical demand and therefore goes unused, effectively costing more money.


Developers need to be mindful not to lock in the energy profile of a building, as the future may bring new efficiency measures and a rise or fall in energy demands.

Capstone microturbines are modular and flexible. They can be used under low electrical demand or under high demand. The machines are flexible and therefore a stable investment, as the discrepancies between predicted and actual electrical demands are allowed for. Microturbines also are an ultralow emission generator, with NOx emissions so low, they do not require any additional treatment, which leads to significant savings for their users.

Connecting to the network 

It is increasingly becoming more complex to connect to the electrical network. While most buildings are connected to the grid for half or more of their electrical supply, the system Optimal uses with our Capstone microturbines is inverter based, and therefore doesn’t contribute to fault current. This allows for a much simpler process to connect into the network, and causes fewer problems.

Optimal in action

The Walker Corporation Collins Square development has recently had great success with Capstone co and trigeneration microturbines. Currently, two of the Collins Square Melbourne towers have been built with 600KW Capstone units, and there are two more soon to be completed. These buildings consistently meet their 5 and 6-star energy ratings, and thus successfully fulfil their requirements as economical, emissions saving machines.