Solar for a Perth holiday home or investment property: does it stack up?

Solar is one of the best investments available for an occupied Perth home — but what about a holiday property that's vacant most of the year? The economics are fundamentally different, and the decision requires a different analysis.

The core challenge: self-consumption

Solar savings come from two sources:

1. Self-consumed solar (electricity you use instead of buying from the grid) — saves 33.26c/kWh
2. DEBS export credits (electricity exported to Synergy) — earns 2c or 10c/kWh

A permanently occupied home might self-consume 35–65% of its solar generation, getting most of its value at 33.26c/kWh.

A holiday home vacant for 300 days/year self-consumes almost nothing during that vacant period. Refrigerators and alarm systems draw perhaps 100–200W continuously, but solar produces 3–7kW during daylight. Nearly all of it exports at DEBS rates.

DEBS export return calculation for a vacant property:

• 6.6kW system, 65 occupied days/year (including stays by owner/guests)
• Generating approximately 9,500 kWh/year
• 300 vacant days: approximately 8,100 kWh generated, 7,800 kWh exported
  • Peak DEBS: say 30% falls 3pm–9pm = 2,340 kWh × 10c = $234
  • Off-peak DEBS: 70% = 5,460 kWh × 2c = $109
  • Subtotal: $343 for vacant period
• 65 occupied days: approximately 1,400 kWh generated, 700 kWh self-consumed + 700 kWh exported
  • Self-consumed savings: 700 kWh × 33.26c = $233
  • DEBS: 700 kWh × average 6c = $42
  • Subtotal: $275
• Total annual benefit: approximately $618 on a system costing $7,000

Payback on this scenario: approximately 11.3 years. Compare to a permanently occupied home at 3–4 year payback.

When it improves: holiday rentals

If the property is a short-term rental (through Airbnb or similar), occupancy rates change the calculation. A coastal property with 60% occupancy (219 days/year) generates significantly more self-consumption:

• 219 occupied days × average daily consumption 12 kWh = 2,628 kWh of potential self-consumption
• With 6.6kW solar generating more than consumption most days, self-consumption might be 50% of occupied-day generation
• Annual benefit: approximately $900–$1,200 at current rates

Holiday rental payback: approximately 6–8 years. Still longer than owner-occupied, but reasonable.

The supply charge factor

An often-overlooked consideration: the supply charge (119.24c/day = $435/year) applies whether or not the property is occupied or generating solar. For a vacant property, you're paying this connection fee all year for limited benefit.

Some owners of vacant holiday homes switch to a no-supply-charge plan (if available in their area) or temporarily disconnect Synergy supply. Note that disconnecting supply also pauses DEBS credits, so this trade-off needs careful calculation.

Remote monitoring for absent properties

If you can't be at the property to notice a fault, monitoring is essential:

Inverter app monitoring: All major inverter brands have cloud monitoring. Set up email or push notifications for:

• Generation below threshold (indicates panel fault or inverter issue)
• Inverter offline (indicates network or power issue)
• Error codes

Smart plug on the refrigerator: Ensures the refrigerator is actually consuming power (confirming power hasn't tripped). A smart plug reporting zero draw from the fridge indicates a circuit trip.

Holiday home security cameras: Most cameras report loss of power/connectivity — an indirect signal that the solar or main power has failed.

Investment property (permanently tenanted)

A tenanted investment property has permanently occupied economics — but the benefit goes to the tenant, not the landlord.

The landlord's dilemma: Installing solar reduces the tenant's electricity bill (they benefit from self-consumed solar) but the tenant pays the electricity bill, not the landlord. The landlord pays for the system and doesn't directly recoup the savings.

What does benefit the landlord:

• Property value premium (estimated 3–5% for solar-equipped properties in Perth)
• Potential to charge a slightly higher rent due to reduced tenant energy costs
• Differentiated listing in a competitive rental market

WA tenancy rules: Landlords cannot directly charge tenants for electricity generated from a solar system without specific arrangements in the lease. Standard practice is that the tenant benefits from solar while paying their own Synergy bill.

For investment properties, the solar case often rests on capital value improvement rather than direct cash flow — a different analysis to owner-occupied solar.

DEBS rate calculations use Synergy rates effective 1 July 2026. Holiday occupancy assumptions are illustrative. Actual returns depend on occupancy rate, consumption patterns, and system size.