The Home with Zero Energy Bills*

Proven Performance, Not Just Theory

Over 12 months of independent monitoring of Green Homes Demonstration Home. in Bathurst, NSW, confirms what we’ve always known. Green Homes perform in the real world, not just on paper.

The Results Speak for Themselves

Heating Demand:
The home used only a fraction of the energy projected by NatHERS, and less than 3% of the average for Climate Zone 65.

Cooling Demand:
Virtually zero energy use for cooling, even through the summer months.

Comfort:
The home maintained an average indoor temperature of 20.3 °C year-round, with consistently lower indoor humidity compared to outside conditions.

Energy Bills:
None. The home operated in an off-grid capacity, with no power costs throughout the year.

Real Data. Real Homes. Real Results.

The chart below visualises these remarkable outcomes, comparing the Bland Home’s actual performance against NatHERS modelling and Climate Zone 65 averages.
The green bars represent the demonstration home, a powerful illustration of how far ahead we are in sustainable design and real-world energy performance.

Weekly snapshot. How are doing in peak summer?

I’ve been keen to see how the home performs during the peak of summer, and now that we have some data, it’s been interesting to analyze the key insights. This summer has been wetter than expected, which has kept daytime temperatures lower while maintaining warmer nights. In passive solar homes, internal temperatures can build up without ventilation on cooler nights, particularly when there is east- and west-facing glass.​

The Enervaro monitoring and control system has been performing well. The first chart shows a typical day where the hot water system is programmed to turn on only when solar power is available, reducing reliance on grid or battery energy and minimizing costs.

The second chart covers the month of January, with a noticeable drop in energy use during the second half while we were away. Before that, daily energy demand remained fairly steady between 14 and 18kWh. On average, we used 60% of our daily energy during solar hours—directly from the sun—helping to reduce the need for battery or grid power.

Weekly snapshot. How are we doing in early spring?

Ater a particularly wet and overcast winter, we’re finally enjoying some warmer weather! With clear blue skies and bright sunshine, our home begins to warm up early in the morning, gradually reaching its peak during the day, and then effectively retaining that heat overnight. Our motto? “Heat up quickly, lose heat slowly!”

The chart below illustrates data from temperature sensors placed throughout the house. It highlights a significant contrast between the outdoor temperature (shown in green) and the temperatures in various rooms inside. On average, the indoor temperature was 20.9°C—over 8°C warmer than the outside!

But what about energy? 

For this home, there is no connection to the local energy network (‘the grid’). All our electricity comes from an 8.4kW solar array and a Tesla Powerwall 2. This is a relatively small system for an ‘off-grid’ home, which is great because we wanted to test how energy-efficient we can be! Most people don’t want or need to be off-grid, but being energy efficient always makes sense to save money and the environment.