Should you invest in insulation or solar panels?
The answer is both
Are you designing a new home or renovation, or finished one recently?
Across Australia, there are national requirements to design and build energy-efficient homes. It is referred to as complying with the NatHERS scheme. A home must be at least 6 stars when assessed for its energy efficiency. The star rating goes from 1 star to 10 stars.
A 6-star home isn’t that great, it’s just a minimum requirement.
These regulations exist to ensure houses and apartments are built to efficiently stay within a set temperature range, through summer and winter. There are other requirements too, regarding specific heating and cooling energy use.
Why you need thermal efficiency and solar panels
We have completed several of these projects to assess the sustainability, water, and energy efficiency of homes as part of planning applications.
We find that clients expect that the rating can be achieved by adding solar panels and batteries. But it can’t! One is demand and the other is supply.
Our modeling, shown in Figure 1, shows that it is the combination of both of these initiatives (efficiency and solar panels) that saves energy and reduces the use of the electricity grid.
Figure 1: Thermal efficiency and solar generation modelling. Graph shows that the combination of thermal efficiency and more solar panels, saves energy and reduces use of the grid.
Reducing energy demand on the grid
A 6-star home in Melbourne can consume 114 MJ / m2 per year (to comply with a 6-star NatHERS load).
But a 6.5 star home, with a 3 kW solar system would use 35% less energy from the grid and only 73 MJ / m2 per year.
More efficiency and more solar on homes would see the total energy demand from the grid drop by 65%. Or more if you aim for a really efficient home.