Case Study: How a Kiama Family Cut Their Power Bill by 78%

The Richardson family in Kiama cut their quarterly electricity bill from $1,180 to $260 — a 78% reduction — after installing a 10kW solar system with a 10kWh battery in early 2026. Here's exactly what they installed, what it cost, what they now save every year, and what they'd do differently if they were starting again. If you're weighing up solar for a South Coast home, this is the kind of real-world case study that matters more than a brochure.

Meet the household

The Richardsons are a family of four living in a 4-bedroom weatherboard home on a north-facing block in Kiama Downs. Like many South Coast families, they have:

• Two working parents (one fully work-from-home, two days hybrid for the other)
• Two school-age kids
• Ducted reverse-cycle air conditioning (installed 2021)
• A swimming pool with a standard variable-speed pump
• One EV, charged at home most nights
• An induction cooktop and electric hot water (heat pump, installed 2023)

In other words: fully electrified, modest-to-high electricity consumption, and classic candidates for solar + battery. Their pre-install electricity usage averaged around 28 kWh per day, spiking above 40 kWh on hot summer days with the pool pump, AC and EV charging all running.

The system they installed

After reviewing three quotes from Illawarra and South Coast installers, they chose Coastal Solar Co. for a 10kW + 10kWh battery package:

• 24 x Trina Vertex S+ 415W panels (total 9.96kW DC) — mounted on the north-facing rear roof and a smaller east-facing portion
• Sungrow SH10RT hybrid inverter — a three-phase hybrid suitable for the Richardsons' existing three-phase supply
• Sungrow SBR096 10kWh LFP battery (three 3.2kWh modules stacked)
• Monitoring via the Sungrow iSolarCloud app with real-time production and battery state-of-charge data

Why they chose 10kW rather than 6.6kW

Three reasons: (1) The roof easily fit 10kW, (2) they wanted to charge the EV from solar rather than grid during daylight hours, and (3) the marginal cost of upgrading from 6.6kW to 10kW was only about $3,200 — cheap generation for a household with high daytime and evening load.

The real cost — before and after rebates

Here's the transparent breakdown:

• 10kW solar system (retail): $10,800
• Sungrow 10kWh battery (retail): $11,500
• Installation, cabling, commissioning: $3,450
• Subtotal retail: $25,750
• Federal STC rebate (10kW system, Zone 3): –$3,950
• Cheaper Home Batteries Program rebate: –$2,000
• Net out-of-pocket: $19,800

They paid via an interest-free green loan through Brighte, structured as $329/month over 60 months — which is substantially less than their old electricity bill.

What happened to the bills

The system was switched on in late January 2026. Their first full quarter of operation (Feb–April 2026) showed:

• Pre-solar average quarterly bill (2024–25): $1,180
• First quarter post-install bill (Feb–Apr 2026): $260
• Solar generation in the quarter: 3,120 kWh
• Self-consumption rate: 68% (including battery use overnight)
• Export to grid: 985 kWh (at 7.2¢/kWh feed-in = $70 credit)
• Grid imports (mostly overnight EV charging on off-peak rate): 480 kWh

A 78% reduction in electricity costs in their first full quarter. And Kiama's summer-autumn transition isn't even peak generation — yearly bills are projected to drop even further as winter loads are offset by battery discharge in the evening.

Annual savings and payback

Extrapolating from the first quarter and modelling typical South Coast seasonal variation, the Richardsons' projected annual numbers are:

• Old annual electricity cost: ~$4,720
• New annual electricity cost: ~$1,300
• Annual savings: $3,420
• Projected simple payback: 5.8 years on the net $19,800 spend
• Expected 15-year net benefit: $31,500+ (assuming 3% annual retail electricity price inflation)

After payback, the system continues producing power essentially for free (minor battery capacity fade aside) until the inverter reaches end of life — typically year 12–15.

Use our free Solar Savings Calculator to see your personalised payback period.

What they'd do differently

We asked the Richardsons what, with the benefit of hindsight, they'd change. Their answers:

1. They'd have installed a year earlier

"We waited 18 months because we weren't sure if battery prices would fall further. They did — but only by about 8%, which we more than lost in electricity bills over those 18 months." (Mrs Richardson)

2. They'd have gone for a bigger battery

"On hot summer nights with the AC running, we do occasionally draw from the grid around 9pm. A 13kWh or 16kWh battery would have covered us fully. The marginal cost would have been worth it." (Mr Richardson)

3. They'd have added an EV charger with solar-diverter

"We charge the EV from the grid overnight on a cheap rate, but if we had a smart EV charger that prioritised solar during the day, we'd be fully off-grid essentially." Many modern hybrid inverters (including the Sungrow SH10RT) support smart EV charging integration — worth planning for at install time.

Why this matters for your Kiama or South Coast home

The Richardsons aren't an unusual case. Here's why similar households across Kiama, Gerringong, Berry, Shellharbour and Bombo are seeing similar results in 2026:

• Strong South Coast irradiance: Kiama averages 4.8 peak sun hours per day year-round — among the best in NSW.
• North-facing coastal lots: Most Kiama Downs and Gerringong homes have unshaded north or north-east aspects.
• Full electrification: Heat pump hot water, induction cooktops, EVs and ducted AC create the exact load profile that rewards solar + battery.
• Endeavour Energy connection: Straightforward grid approvals and no export-limit issues for 10kW systems in most South Coast streets.
• Current rebate stack: STC plus Cheaper Home Batteries Program together knock ~$6,000 off a 10kW + 10kWh combo in 2026. This won't last — STC steps down again on 1 January 2027.

Frequently Asked Questions

Can I get similar results without a battery?

You'll still save substantially with solar-only — typically 50–65% off a typical Kiama or Illawarra bill if you shift laundry, dishwashing, pool pump and EV charging to daytime. The jump from 65% to 78%+ comes from battery storage, which lets you use your own solar overnight rather than importing at full retail rates.

How much does a 10kW + 10kWh system cost in 2026?

After combined STC and Cheaper Home Batteries rebates, you're looking at $18,500–$21,500 out of pocket for a quality install with reputable brands (Trina/Jinko panels, Sungrow/Fronius inverter, Sungrow/BYD/Tesla battery). Cheaper packages exist but almost always use lower-tier components with shorter effective warranties.

Does my roof need to face north for these results?

North-facing roofs produce the most total annual generation, but east and west-facing panels can actually improve self-consumption by spreading generation across morning and afternoon. A 50/50 east-west array often ends up saving more on bills than a pure-north array, even though total generation is slightly lower.

Will the Cheaper Home Batteries Program still be available later this year?

The program is funded and running as of April 2026, but the federal government has flagged a review for late 2026. Rebate amounts have historically stepped down over time rather than suddenly ending. If you're on the fence, booking in 2026 locks in current rebate levels.

How long did the Richardsons' install take end-to-end?

Twenty-one days from signed contract to system switched-on. Install itself ran across two days (solar on day one, battery commissioning on day two). Grid approval through Endeavour Energy took 8 business days. Meter reconfiguration took another 7 days post-install for the feed-in tariff to activate.

Ready to get your personalised quote? Contact our CEC-accredited team — we'll call you back within 5 minutes.