Question 1

How do the federal STC capacity tapers work?

Accepted Answer

Under the framework in force since 1 May 2026, federal STCs are tapered by battery size. The 0–14 kWh band receives 100% of STCs, 14–28 kWh receives 60%, and 28–50 kWh receives 15%. The taper applies to the entire battery capacity, not only the portion above 14 kWh. A 20 kWh battery now generates roughly $4,150 less in STCs than a comparable system claimed under the pre-May rates. Use our STC Timing Calculator to see how the taper maps to your chosen size.

Question 2

Why does battery size matter so much for the federal rebate?

Accepted Answer

The capacity taper is steep above 14 kWh, so battery size now drives most of the rebate outcome. A 13.5 kWh battery still receives the full STC factor (~$2,925 at current rates). A 20 kWh battery receives only 60% of STCs across the whole pack. For most Perth households, 10–14 kWh is the band that balances self-consumption, VPP earnings, and rebate value.

Question 3

How much do STCs decline each year until 2030?

Accepted Answer

STCs are based on deeming periods, which count the years remaining until 2030. The 2026 H2 factor is 6.8 STCs/kWh combined with the capacity tapers (60% for 14–28 kWh, 15% for 28–50 kWh). In 2027 the factor steps down to 5.7–5.2 STCs/kWh, with further reductions through 2030. For a 13.5 kWh battery the rebate progresses roughly $2,925 (current) → $2,500 (2027) → $2,100 (2028) → $0 (2030). The 1 May 2026 change was the largest single reduction in the program to date.

Question 4

Are installers booked out months ahead?

Accepted Answer

Most Perth installers have 2–4 month wait times. Demand stayed high through the 1 May 2026 transition. Some installers honour the STC rate at quote or deposit time rather than installation time, so ask about this policy when comparing quotes. Getting quotes early protects you from further rate drops, even if physical installation is months away.

Question 5

How much does a solar battery cost in Perth?

Accepted Answer

Battery costs in Perth range from $8,000 for a 5 kWh system to $23,000+ for 20 kWh systems. The 10–13 kWh range typically costs $12,000–$16,000 installed. Pricing varies by brand, capacity, and installation complexity. Federal STCs reduce costs by roughly $1,900–$3,000 for larger batteries under the current capacity-tapered framework (factor 6.8 × $39.9/STC, with tapers above 14 kWh). The WA Residential Battery Scheme adds up to $1,300 for Synergy customers, for eligible batteries up to 10 kWh.

Question 6

What rebates are available for batteries in WA?

Accepted Answer

WA homeowners on the Synergy network can stack three rebates. The federal STC rebate is worth roughly $2,700–$3,500 for popular 10–13 kWh batteries under the current 6.8 STCs/kWh factor (less for larger batteries due to the capacity taper). The WA Residential Battery Scheme adds $130/kWh up to $1,300, capped at 10 kWh of eligible storage. The Distributed Energy Buyback Scheme (DEBS) pays a 10c/kWh export rate during peak hours. VPP participation is required for the WA battery rebate.

Question 7

What size battery do I need for my Perth home?

Accepted Answer

Most Perth homes need 10–13 kWh of usable capacity. A 10 kWh battery suits 3–4 bedroom homes using 20–30 kWh/day. 13 kWh and above is better for larger homes, pools, or EV charging. Use the calculator for a personalised recommendation based on your actual usage, tariff, and solar system size.

Question 8

How long does a solar battery last?

Accepted Answer

Quality batteries last 10–15 years. Warranties typically cover 10 years or a specific throughput (for example 36–58 MWh). Degradation rates vary by chemistry: LFP cells (BYD, Tesla) degrade slower (1.8–2.5%/year) than NMC cells (2.5–3.5%/year). After 10 years, expect 70–85% of original capacity remaining.

Question 9

Can I add a battery to my existing solar system?

Accepted Answer

Yes. AC-coupled batteries (Tesla Powerwall, Alpha ESS) work with any existing solar system. DC-coupled batteries (BYD, Sungrow SBR) require a compatible hybrid inverter. If your current inverter is incompatible, you may need to upgrade or add a second inverter. Our installer partners can assess the system and recommend a retrofit option.

Question 10

What is the payback period for a battery in Perth?

Accepted Answer

Typical payback periods in Perth are 8–12 years, depending on usage patterns, tariff, and rebates. Homes on the Synergy A1 tariff with high evening usage see faster payback (7–9 years). VPP participation can shorten payback by 1–2 years. The calculator provides personalised payback estimates based on your specific situation.

Question 11

Do batteries work during blackouts?

Accepted Answer

Most modern batteries support backup power, but it requires a specific installation (backup gateway and switchboard work). You can choose whole-home backup or essential circuits only (lights, fridge, internet). Backup capability adds $1,000–$2,000 to installation costs. Not every battery supports backup; check the specifications before purchasing.

Question 12

What is DEBS and how does it work?

Accepted Answer

DEBS is Synergy's time-of-use export tariff. You earn 10c/kWh for solar exported 3pm–9pm (peak) and 2c/kWh outside those hours. Batteries maximise DEBS value by storing solar during the day and exporting during the 10c window, earning 5× more than off-peak exports.

Question 13

Should I join a VPP program?

Accepted Answer

Synergy Battery Rewards pays 70¢/kWh during VPP activation events. These typically fire 15–25 times per year. For a 10–13 kWh battery at ~70% discharge, that works out to roughly $100–180/year. You get the income and a contribution to grid stability. In exchange, backup capacity is reduced during the rare events that fire, and the battery cycles slightly more.

Question 14

AC-coupled or DC-coupled battery - which is better?

Accepted Answer

AC-coupled batteries (Tesla, Enphase) retrofit onto any solar system and run at 89–93% efficiency. DC-coupled batteries (BYD, Sungrow) run at 95%+ efficiency but require a compatible hybrid inverter. For new installations, DC-coupled saves a conversion step. For retrofits, AC-coupled is simpler to wire in.

Question 15

Do I need Western Power approval for a battery?

Accepted Answer

Yes. All battery installations require Western Power approval. The installer handles this through the ESM (Electricity Supply Management) portal. Approval typically takes 5–10 business days. Western Power checks your export limit, inverter capacity, and network compatibility. SAA-accredited installers run this process routinely.

Question 16

Can I finance a solar battery?

Accepted Answer

Yes. Green loans from lenders such as NICU, Community First, and Parker Lane sit around 6–8% p.a. for battery purchases. Loan terms typically range from 3–7 years. Some installers offer in-house financing. Compare loan interest against the cash-purchase savings figure to confirm financing doesn't wipe out the payback.

Question 17

What is CSIP-AUS and why does it matter?

Accepted Answer

CSIP-AUS (Common Smart Inverter Profile – Australia) is the communication standard required for VPP participation in WA under the framework in force since 1 May 2026. It lets Synergy remotely manage your battery during grid events. Without CSIP-AUS compliant equipment, you cannot participate in Battery Rewards (70¢/kWh), access Tier 2 dynamic exports, or claim the WA battery rebate. Check the Synergy Supported Solutions List (SSL) to confirm equipment compatibility before purchasing.

Question 18

How hot is too hot for a battery in Perth?

Accepted Answer

Most batteries operate safely up to 45–50°C ambient, though output may derate above 35–40°C. LFP cells (BYD, Tesla Powerwall 3, Sungrow) handle heat better than NMC cells. Installation location matters more than brand. A garage or south-facing shaded wall is ideal. Avoid west-facing walls that catch the afternoon sun. Your installer should assess thermal conditions during the site visit.

Question 19

What happens to my battery during a VPP event?

Accepted Answer

During a VPP activation event, Synergy remotely discharges your battery to export power to the grid. Events typically last 2–3 hours and fire during peak demand periods (usually hot summer afternoons, 3–9pm). You receive 70¢ for every kWh exported. Your home continues to draw power normally; the battery discharges faster than usual. You typically receive notification 1–2 hours before an event starts. Events fire 15–25 times per year.

Question 20

What's the difference between nominal and usable capacity?

Accepted Answer

Nominal capacity is the total storage in the cell (for example 13.5 kWh). Usable capacity accounts for depth-of-discharge limits; most batteries reserve 5–10% to protect longevity. A 13.5 kWh battery might have 12–13 kWh usable. Compare usable capacity, not nominal. Round-trip efficiency (92–98%) means you get slightly less energy out than you put in. A battery storing 10 kWh might deliver 9.2–9.8 kWh.

Question 21

Do I need to upgrade my switchboard for a battery?

Accepted Answer

It depends on the current switchboard's condition and age. Modern switchboards with safety switches usually handle a battery addition without major upgrades. Older switchboards (pre-1990s) may need updating for safety compliance, adding $500–$1,500 to installation costs. If you want backup power, additional work is needed to separate essential circuits. The installer assesses this during the site visit and quotes accordingly.

Question 22

Can I install a battery myself to save money?

Accepted Answer

No. Australian law requires battery installation by licensed electricians, and rebate eligibility requires SAA-accredited installers. DIY installation voids warranties, makes you ineligible for STCs and state rebates, and creates serious safety risks. High-voltage lithium batteries can cause fires if installed incorrectly. Any cost savings from DIY (if it were legal) would be wiped out by lost rebates and the risk profile.

Question 23

How do I monitor my battery performance?

Accepted Answer

Most modern batteries include smartphone apps that show real-time charging and discharging, daily and monthly energy flow, state of charge, and system health. Tesla, BYD, Sungrow, and most major brands ship dedicated apps. Some systems integrate with home assistants or third-party monitoring platforms. Good monitoring helps you optimise usage and catch issues early. Your installer should set up monitoring during commissioning.

Solar & battery FAQ for Perth

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Solar & battery FAQ for Perth

Get matched with a Perth installer