Solar vs battery in WA - which first?

If you have to choose, install solar first. If you can do both, install them together as one job. Here's the full decision framework with cost, payback and a head-to-head comparison.

Head-to-head: Solar vs Battery in WA (2026)

The combined install - the smart play

If you don't have solar yet, the right move is to install solar and battery together as one bundled job. Three reasons:

• Shared labour. Most of the day-of-install work (scaffolding, mounting, wiring through the switchboard) overlaps. Combined installs save $1,000–$1,500 vs separate jobs.
• Hybrid inverter cost is bundled. A standalone battery retrofit often requires replacing your existing solar inverter with a hybrid model - adding $1,500–$2,500. A combined install includes the hybrid inverter as the only inverter needed.
• Maximum rebate stack. You capture solar STCs + WA battery rebate + federal Cheaper Home Batteries rebate in one application cycle. Total off can exceed $10,500 on a typical setup.

Typical combined-install price in 2026: $17,000–$21,000 list, $5,000–$7,000 net after all rebates. For a 6.6 kW solar + 13.5 kWh battery setup that's expected to save $2,000+/year.

If you have to choose: install solar first

Three reasons solar wins the "what first" decision:

1. Faster payback even without battery

A standalone 6.6 kW solar system in Perth pays back in 4–5 years from bill reduction + DEBS exports. A standalone battery without solar takes 8–12 years to pay back via time-of-use arbitrage. Solar's value is more immediate.

2. Battery without solar has weak economics

A battery's primary value is storing your own free solar generation for evening use. Without solar, the battery is just arbitraging cheap off-peak grid for expensive peak grid - earning roughly half the value per kWh cycled.

3. Solar is harder to retrofit elegantly

Adding solar later requires inverter changes if you've already installed a battery. Adding a battery to an existing solar system is straightforward if you've picked a hybrid-ready inverter from the start.

When battery-first makes sense

Three edge cases:

• You can't install solar. Heritage overlay, strata refuses approval, north-facing roof blocked. A standalone battery still claims both rebates and works on time-of-use arbitrage (slower payback, but real).
• You're worried about hitting the 100,000-household state rebate cap. The WA state rebate runs out when 100k homes claim, regardless of timing. Locking your battery rebate slot now and adding solar later is a defensible move - but only if you're sure solar will follow.
• Your existing inverter is past warranty and likely to die. Replace it with a hybrid inverter + add a battery in one combined job. Solar panels (the long-lived part) stay.

The decision framework

Answer these three questions:

1. Do you have solar already?
   Yes → battery is next.
   No → ideally do both at once.
2. Is your existing solar 5+ years old?
   Yes → consider replacing the inverter with a hybrid at the same time as the battery install. The original solar panels still have 15+ years of life.
   No → straightforward battery retrofit.
3. Are you considering an EV in the next 5 years?
   Yes → size both solar (10 kW+) and battery (16–20 kWh) accordingly.
   No → standard sizing (6.6 kW solar, 10–13.5 kWh battery).

What does this look like in dollars?

Three real-world scenarios:

Scenario A: Existing 6.6 kW solar, add battery

• Existing solar from 2021 (still under warranty)
• Add 13.5 kWh Powerwall 3: $14,000 list
• State rebate (Synergy): $5,000
• Federal rebate: $5,022
• Net: ~$3,978. Payback: 2.9 years.

Scenario B: No solar, install solar + battery together

• 6.6 kW solar: $5,500 (post-STC)
• 13.5 kWh Tesla Powerwall 3: $14,000 list
• State rebate (Synergy): $5,000
• Federal Cheaper Home Batteries: $5,022
• Net combined: ~$9,478. Payback: ~5 years.

Scenario C: No solar, install battery only

• 13.5 kWh Powerwall 3: $14,000 list
• State rebate: $5,000
• Federal rebate: $5,022
• Net: ~$3,978. But annual savings only ~$700 (no solar to store).
• Payback: 5.7 years. Workable but not great.

What this means for you

For most WA homeowners without existing solar: bundle both into one install. Smaller upfront commitment, faster payback, maximum rebate stack.

For WA homeowners with existing solar: just add a battery. The maths is exceptional in 2026.

For WA homeowners who can't install solar (heritage, strata, north-roof issues): consider a standalone battery for time-of-use arbitrage. Slower payback, real backup power benefit.