Each scenario below is an illustrative model of a Perth Synergy household moving through bill analysis, system sizing, installation, and a first year on solar and battery. The figures are modelled on real WA tariffs, rebates and 2025–2026 system pricing. They are not measured customer bills. Run the calculator to estimate your own.
Bill amounts shown are the Synergy billing-period totals. The 25-year ROI compounds each year's saving forward using the published Synergy price trend and reduces it for panel degradation, then subtracts what the household paid after rebates. Each scenario assumes the household stays on the same plan post-installation, and every residual bill still carries the daily supply charge, which solar does not offset.
Where a scenario shows no export credit, that follows the buyback scheme's capacity limit for the modelled system. Buyback schemes are set by the state government and administered by your retailer, and eligibility depends on your own system and where you live, so check what applies to you with Synergy or Energy Policy WA before counting on export income either way.
Baldivis, WA · Family of 4, 4-bedroom home
Modelled annual electricity cost falls from $3280 to $835, a saving of $2445 a year.
42/100BillWise Score
Bill (per period): $820. Tariff: A1 (Flat Rate).
88/100BillWise Score
Bill (per period): $209. Annual Cost: $835.
Key Issues:
$2445
Annual Savings
In this scenario the household pairs a 6.6kW solar system with a 10kWh battery, achieving ~70% self-consumption. The modelled bill falls by roughly three quarters once STC and WA Battery Scheme rebates are applied.Basis: Synergy A1 tariff (33.26c/kWh) + DEBS export at the off-peak rate (2c/kWh) + WA Battery Scheme rebate.
Joondalup, WA · Retired couple, 3-bedroom home
Modelled annual electricity cost falls from $1940 to $815, a saving of $1125 a year.
38/100BillWise Score
Bill (per period): $485. Tariff: A1 (Flat Rate).
82/100BillWise Score
Bill (per period): $204. Annual Cost: $815.
Key Issues:
$1125
Annual Savings
In this scenario a daytime-home retired couple installs a 5kW solar system sized to their consumption, achieving ~40% self-consumption. The system is paid off in roughly three years against the modelled saving.Basis: Synergy A1 tariff (33.26c/kWh) + DEBS export at the off-peak rate (2c/kWh) + STC rebate.
Canning Vale, WA · Professional couple with EV, 4-bedroom home
Modelled annual electricity cost falls from $3920 to $824, a saving of $3096 a year.
35/100BillWise Score
Bill (per period): $980. Tariff: A1 (Flat Rate).
91/100BillWise Score
Bill (per period): $206. Annual Cost: $824.
Key Issues:
$3096
Annual Savings
In this scenario an EV-owning household pairs an 8kW solar system with a 10kWh battery and shifts EV charging to the daytime solar window, achieving ~75% self-consumption. At 8kW the system sits above the DEBS eligibility cap, so it is paid nothing for what it exports and every dollar of the saving comes from electricity it no longer buys. The saving shown counts electricity only, not the fuel it stops buying.Basis: Synergy A1 tariff (33.26c/kWh), the rate the avoided grid import is priced at + no DEBS export payment (above the 6.6kW DEBS eligibility cap) + WA Battery Scheme rebate. Moving overnight EV charging to the Synergy EV Add-On rate (19.92c/kWh) is a further saving this scenario does not count.
Rockingham, WA · Young family with 2 kids, 3-bedroom home
Modelled annual electricity cost falls from $2720 to $1395, a saving of $1325 a year.
44/100BillWise Score
Bill (per period): $680. Tariff: A1 (Flat Rate).
84/100BillWise Score
Bill (per period): $349. Annual Cost: $1395.
Key Issues:
$1325
Annual Savings
In this scenario a budget-conscious family installs 6.6kW of solar (no battery) with partial daytime occupancy, achieving ~35% self-consumption. Roughly two thirds of the generation is exported, and export earns far less than the retail rate it would have offset.Basis: Synergy A1 tariff (33.26c/kWh) + DEBS export at the off-peak rate (2c/kWh) + STC rebate.
Mandurah, WA · Family with pool, 4-bedroom home
Modelled annual electricity cost falls from $3800 to $1478, a saving of $2322 a year.
36/100BillWise Score
Bill (per period): $950. Tariff: A1 (Flat Rate).
86/100BillWise Score
Bill (per period): $370. Annual Cost: $1478.
Key Issues:
$2322
Annual Savings
In this scenario a pool-owning household installs 10kW of solar and shifts the pool pump to the midday solar window, achieving ~45% self-consumption. At 10kW the system is above the DEBS eligibility cap, so it earns nothing for export and is worth installing only because the pump and the pool soak up the generation on site. Shifting the pump is what does the work: the same system with the pump running overnight would save materially less.Basis: Synergy A1 tariff (33.26c/kWh), the rate the avoided grid import is priced at + no DEBS export payment (above the 6.6kW DEBS eligibility cap) + STC rebate. Moving the pump to a Midday Saver plan is a further saving this scenario does not count.
Analyse your bill for a personalised BillWise Score, then model your own solar and battery savings.
