Self-consume vs export: solar energy strategy for Perth households

The fundamental economics of Perth solar come down to a single number: 31.26c/kWh. That's the difference between the value of a kilowatt-hour you self-consume (saves you 33.26c in grid imports) and one you export during the off-peak window, when most solar is sent to the grid (earns you 2c under the Synergy DEBS scheme). For the smaller share of exports that land in the 3pm-9pm peak window, the DEBS rate is 10c/kWh, narrowing the premium to 23.26c/kWh.

Every decision about how to use your solar (when to run appliances, whether to add a battery, which tariff to choose) can be evaluated against this 31.26c premium (23.26c for the peak-window share of exports).

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Why self-consumption beats export by such a wide margin

In some countries, solar feed-in tariffs are set at or near the retail rate. Australia's national and state policies moved away from that model after the early 2010s solar boom strained retailer cross-subsidies. Western Australia's current DEBS rate (10c/kWh during the 3pm-9pm peak window, 2c/kWh off-peak) reflects the actual marginal cost of wholesale electricity, not the retail value.

As a Perth solar household:

• Every kWh you self-consume saves 33.26c (the A1 import rate as of July 2026)
• Every kWh you export earns 2c off-peak (9am–3pm and other off-peak hours), or 10c during the 3pm–9pm peak window

The 31.26c gap for typical off-peak exports (23.26c for exports that land in the 3pm-9pm peak window) is the incentive to consume solar when it's available rather than export it. The more load you can shift to daytime hours, the better your overall savings.

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What practical self-consumption looks like

For a typical Perth household that's absent during the day (everyone at work), daytime self-consumption might be 20–35%: the fridge, standby devices, and whatever a timer or smart plug switches on. Most generation is exported.

For a household with someone home during the day, or with automated load control, self-consumption can reach 50–70%. At that level:

• A 6.6kW system generating ~9,800 kWh/year at 65% self-consumption: 6,370 kWh self-consumed, 3,430 kWh exported (roughly 515 kWh in the 3pm-9pm peak window and 2,915 kWh off-peak, based on the typical 15%/85% peak/off-peak export split)
• Value: 6,370 × 33.26c + (515 × 10c + 2,915 × 2c) = $2,119 + ($52 + $58) = $2,119 + $110 = $2,229/year
• Compared to 30% self-consumption: 2,940 self-consumed + 6,860 exported (1,029 peak, 5,831 off-peak) = $978 + ($103 + $117) = $978 + $220 = $1,198/year
• The additional 35% self-consumption is worth $1,031/year more despite generating the same amount

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How to increase self-consumption in Perth

Shift dishwasher and washing machine to daytime

A dishwasher uses 1–2 kWh per cycle. Washing machine (cold wash) uses 0.3–0.8 kWh per cycle. Running both during peak solar hours (10am–2pm) rather than evening means these loads are covered by solar rather than grid.

Annual saving from shifting both: ~300–400 kWh/year self-consumed instead of exported. At 31.26c premium: $94–$125/year.

Run hot water on daytime electricity (electric storage system)

Electric storage hot water tanks (250L) typically heat 1.5–3 kWh per cycle. Setting the timer to heat during peak solar hours diverts solar into thermal storage, effectively a low-cost battery for hot water.

Annual saving: 400–900 kWh/year depending on system size. At 31.26c premium: $125–$281/year.

EV charging during solar hours

If your EV can be charged at home on a regular schedule, charging during 10am–2pm on a workday captures peak solar generation.

Annual saving: 1,000–2,500 kWh/year depending on EV usage and charge frequency. At 31.26c premium: $313–$782/year.

Battery storage

A battery charges during midday solar surplus and discharges in the evening, effectively converting export (2c off-peak value) into self-consumption (33.26c value) for the stored kWh.

A 10kWh battery at $10,000 installed: if it shifts 2,000 kWh/year from export to self-consumption, the premium value is 2,000 × 31.26c = $625/year. Payback: ~16 years at current rates. Battery payback periods are long at current DEBS and retail rates. The case is strongest for households with very high evening consumption and excellent daytime solar capture already.

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The Midday Saver tariff and self-consumption strategy

If you're on the Synergy Midday Saver tariff:

• Peak: 55.33c/kWh (7–9am, 5–9pm weekdays)
• Off-peak: 24.34c/kWh (other times)
• Super-off-peak: 8.85c/kWh (10am–3pm daily)

On Midday Saver, the analysis changes:

• Solar during 10am–3pm: replaces super-off-peak grid at 8.85c, comfortably better than exporting at only 2c off-peak, but mostly you'll have more solar than load during that window anyway
• Evening peak (5–9pm weekday): grid is 55.33c/kWh: a battery storing solar for this window has a better value case than on A1

Key insight on Midday Saver: The tariff's value for solar households lies more in the low-cost 10am–3pm grid electricity for days when solar is insufficient (cloudy, winter) than in its interaction with solar self-consumption. On a clear day, solar covers the super-off-peak window easily and the question is whether you have loads to fill it.

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How much can you realistically shift?

Most Perth households can shift 5–15% of their generation from export to self-consumption through behavioural changes (timer appliances, daytime hot water). An additional 10–20% is achievable with a battery. Working from home adds another 10–15% from increased daytime load.

Realistic ceiling without major investment: 50–65% self-consumption for an average household. Above 65–70%, you'd need to be home most of the day or have very high daytime loads (pool, EV, ducted AC).

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Self-consuming solar is worth 31.26c/kWh more than exporting during Perth's off-peak export window, and 23.26c/kWh more for the smaller share of exports that land in the 3pm-9pm peak window. Shifting discretionary loads to daytime (dishwasher, washing machine, hot water heating, EV charging) is the lowest-cost way to increase self-consumption. Battery storage is an option with longer payback. The right strategy depends on when your household actually uses electricity.