Every card is picked from the modelled squares in this matrix with fixed rules — same inputs, same picks, nothing decided by AI:
- Energy Idealthe solar size whose grid exports land closest to the site's target export share.
- NPV Maximisingthe square with the highest lifetime value.
- Grant Maximisingthe biggest upfront incentive return, capped at scheme-eligible sizes.
- Self-Sufficiency Maximisingas grid-independent as the numbers still justify.
- Solar Only vs + Batteryoptimised separately — the battery pick is the cheapest one that still captures most of the best storage option's lifetime value.
A card only defaults to + Battery when its payback stays close to the solar-only payback — and nothing larger than your usable roof is ever recommended.
Every recommendation on the project’s Recommendation page comes out of the sizing matrix: a grid where every square is one solar + battery combination, modelled hour-by-hour against your site’s real consumption data (how the modelling works). The scenario cards are not an AI’s opinion — they are picked from that grid with fixed, deterministic rules. Run the same project twice and you get the same picks. This page spells out those rules.
The candidate pool
Before anything is picked, the pool of candidate squares is trimmed: if the project has a roof area set, no system larger than the usable roof capacity is ever considered. Squares with no priced cost are also skipped. What remains — every viable solar size, with and without every battery size — is the pool all four scenarios draw from.
The four scenario cards
Energy Ideal — best overall balance
Takes the solar size whose grid export share lands closest to the site’s target export share (derived from the consumption profile). Intuitively: big enough that most daytime load is covered, not so big that a large slice of generation is sold to the grid at a low feed-in rate. The pick also respects a roof cap and a payback cap when they are set.
NPV Maximising — best lifetime value
Takes the square with the highest net present value — the most lifetime dollars, full stop. This is usually a larger system than Energy Ideal: it spends more capital to capture the last dollar of value, and accepts a slower payback to get it.
Grant Maximising — best incentive uplift
Takes the system with the biggest upfront incentive return (STCs, VEECs, PDRS), capped at the scheme-eligible size — just under 100 kWp where only STCs apply, or 200 kWp where VEECs extend the worthwhile range. Ties are broken by NPV, so among equally subsidised sizes the more valuable one wins. See Australian solar incentives explained for what those schemes are.
Self-Sufficiency Maximising — as grid-independent as the numbers justify
Takes the square with the highest self-sufficiency among the squares that are still NPV-positive. Self-sufficiency always rises with system size, but the biggest systems go NPV-negative — so the rule stops at the edge of profitability rather than at an arbitrary percentage. If nothing is NPV-positive, it falls back to the least-bad square.
Solar Only vs + Battery
Each card’s Solar Only and + Battery versions are optimised separately. Solar-only searches just the “None” battery row of the matrix. The battery pick searches the battery rows — but with an important filter first:
- Only “real” batteries count. A battery qualifies when it lifts self-consumption by at least 5 percentage points over the same-solar solar-only system. This screens out token batteries that exist only to bank a battery subsidy.
- NPV Maximising takes the highest-NPV real battery.
- Energy Ideal takes the knee of the value curve: the cheapest real battery that still captures at least 90% of the best storage option’s lifetime value. Roughly nine-tenths of NPV Maximising’s upside for meaningfully less capital and a faster payback — so Energy Ideal’s battery never costs more than NPV Maximising’s.
- Grant Maximising keeps its capped solar size and pairs it with the best-value real battery at that size, so the card stays a distinct story rather than a clone of NPV Maximising.
When a card defaults to + Battery
A card only pre-selects its + Battery version when the battery’s payback stays close to the solar-only payback (within roughly 1.3×). If storage stretches the payback well past the solar-only figure, the card defaults to Solar Only and leaves the battery as the flip side — visible, but not the recommendation.
Reading the matrix yourself
On the Recommendation page, the ★ marks the recommended system, numbered circles mark the other shortlisted scenarios, hollow rings on the “None” row are their solar-only versions, and a coral ◆C marks your own custom size. Click any modelled square to load that size into Design Your Own — the fixed rules give you a starting point, not a straitjacket.