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When a home is marketed as "net zero," most people assume it produces as much power as it uses. Technically, that's true for most homes carrying the label. But look closer at how that balance is actually achieved, and a problem shows up fast: the power gets made when the sun is out, not when the house actually needs it.
That gap is the subject of a recent SBA webinar, and it's why we think the industry needs a better benchmark than annual net zero: monthly net zero.
The problem with counting by the year
Under the National Construction Code's Trajectory for Low Energy Buildings, the goal by 2030 is for all new buildings to be "zero energy and carbon ready": an efficient thermal shell and appliances, paired with enough on-site solar to hit net zero over a year. It's a good target on paper, but the annual figure hides a seasonal mismatch.
Take a typical 7-star home with a 7kW solar system. Across summer, it produces far more power than it uses, but mostly during the day, when feed-in prices are low. Hot water and other loads still draw power at night, when demand and prices are high. In winter, the pattern flips: solar production drops just as heating demand rises, so the home draws heavily from the grid exactly when the grid is under the most pressure.
Add it up over twelve months and the home reads as net zero. But it's still expensive to run, and still adding strain to the grid at peak times, the very thing Australia's energy transition is trying to avoid. This is the "duck curve" problem: a steep morning demand spike, a midday trough as solar floods the grid, and a sharp evening peak once the sun goes down. More homes built to hit annual net zero without addressing this pattern means more pressure on grid infrastructure, not less.
What monthly net zero looks like instead
A monthly net zero home produces at least as much power as it uses in most months, not just on average across the year. It's a small shift in framing with a big practical consequence: it forces demand reduction first, rather than simply oversizing a solar system to cover an inefficient home.
Real examples make the case well. Two homes built to this standard (8.3 and 8.6 stars, fitted with heat pumps, induction cooking and efficient appliances) are tracked with actual, lived-in data rather than projections. One finished the year at $300 in credit. The other, home to an elderly couple charging an EV on-site, finished $500 in credit on electricity, plus roughly $800 saved on fuel and $300 saved by not running a gas connection, exporting over 9,000 kWh back to the grid across the year.
That's not just a lower bill. A home drawing almost nothing from the grid most of the year, and capable of running independently for days during a blackout, is a genuinely different category of asset: resilient, low-cost to run, and useful to the grid rather than a drain on it.
How to get there
Monthly net zero isn't achieved through a bigger solar system alone. It follows SBA's five-step roadmap, in order:
- Good design – passive solar principles that cut heating and cooling demand before any technology is added.
- Low-impact material selection – lower-carbon materials, addressing embodied carbon alongside operational energy.
- Performance construction – building to the standard the design promises, since performance is easily lost on site.
- Efficient appliance selection – heat pumps for heating, cooling and hot water, induction cooking, LED lighting, high-star appliances.
- Energy generation and offsetting – solar sized to the reduced demand, then batteries to shift generation to when it's actually needed.
Demand reduction comes first for a reason: it's cheaper to shrink the load than to oversize the system covering it, and most homes don't have the roof space to brute-force their way to net zero without addressing efficiency first.
Annual net zero was a reasonable first step for the industry. But as more homes are added to a grid already under pressure, when they draw power matters as much as how much they draw over a year. Monthly net zero is a tougher, more useful target, and one the industry can start building toward today using the resources already on the SBA roadmap.
