Solar and your Christmas electricity bill in Perth

December and January are peak solar generation months in Perth — and also peak electricity consumption months. The coincidence is convenient: the time of year when your Synergy bill would otherwise be highest is also when solar systems generate the most.

Perth's solar peak in summer

In Perth summer (December–January), a typical 6.6kW north-facing system generates:

• Clear day: 30–38kWh
• Overcast day: 10–18kWh
• Average daily generation: approximately 29–33kWh

This compares to winter minimums of 10–15kWh/day. Your solar system generates roughly 2–3× more electricity in summer than winter.

The Christmas demand pattern

Christmas and New Year in Perth create unusual electricity demand:

• People home all day: WFH patterns are reversed — many people are on leave, running air conditioning from morning
• Christmas cooking: oven, multiple appliances, potentially outdoor cooking (barbecue — gas, not electricity)
• School holidays: children home increases daytime consumption
• Extended social gatherings: more appliances, more refrigeration, entertainment systems

For solar households, more people at home during the day is a benefit: daytime consumption increases, self-consuming more solar generation rather than exporting at low DEBS rates.

How solar changes the Christmas bill

Without solar (typical 5-person household, December):

• Daily consumption: approximately 35–45kWh (summer AC-heavy)
• Daily cost at A1 (33.26c): $11.64–$14.97/day
• 30-day December bill: approximately $350–$450

With 6.6kW solar, no battery (A1 tariff):

• Solar generation: ~30kWh/day
• Daytime self-consumption (people home, AC running): ~20kWh
• Evening grid import: ~15–25kWh (post-sunset AC + cooking + entertainment)
• Daily net cost: approximately $5–$8/day
• 30-day December bill: approximately $150–$240 (plus DEBS export credits, ~$0.60/day)

With 6.6kW solar + 10kWh battery (Midday Saver):

• Battery charges during 9am–3pm solar surplus
• Discharges 3pm–9pm during cooking and evening
• Evening peak grid import: approximately 5–10kWh
• Daily cost at peak 55.33c: $2.77–$5.53 for residual evening import
• 30-day December bill: approximately $80–$165

Optimising solar for the Christmas period

Schedule the AC pre-cooling: With people home on school holidays, air conditioning likely runs more continuously. On Midday Saver, the pre-cool strategy (run AC hard from 10am–2:30pm at 8.85c/kWh super off-peak, then coast as the house is already cool heading into the 3pm peak rate) remains effective. Solar generation covers the pre-cool load.

Christmas cooking timing: Traditional Christmas lunch at noon works well for solar households — oven, stovetop, and appliances running during peak solar generation (10am–2pm). Dinner preparation at 6–7pm falls in the peak rate (55.33c/kWh) — use the battery or slow-cook earlier in the day if possible.

Pool pump scheduling: The school holiday period often means more pool use. Pool pump timed to run 9am–3pm uses solar generation at 8.85c/kWh super off-peak (Midday Saver) or free solar self-consumption. Avoid running the pool pump in the 3–9pm peak window.

Fridge and freezer: An extra esky or temporary freezer for Christmas food and drinks adds electricity load. Run these during the day when solar covers the load, or put them in the garage and ensure they're not running in direct sun (ambient heat increases compressor work).

When you're away over Christmas

If the household goes on holiday for 2–4 weeks over Christmas and New Year:

• Solar generation continues but the house is empty — all generation exports
• On DEBS: export earns 2c/kWh (off-peak) or 10c/kWh (peak 3–5pm typically)
• Net: you earn a small credit from export while the house is empty

Battery during absence: With nobody home, the battery charges during the day from solar and has nothing to discharge to in the evening — it may stay partially charged or cycle at low utilisation. This isn't harmful, but you won't maximise value from the battery during the absence period.

Before leaving:

• Set hot water system to "vacation" or "off" mode (no point heating a full tank daily)
• Set AC to off (but check the thermostat is set to a temperature that prevents any connected devices from heat damage if ambient gets very high)
• Leave the pool pump on its normal schedule so the pool doesn't go green

The January Synergy bill after a solar summer

Perth households with solar and battery often see very low January–February Synergy bills:

• Generation high: summer sun + long days
• Self-consumption high: people home, AC running through the day
• Battery captures midday surplus for evening use

For a household on Midday Saver with a 6.6kW solar system and 10kWh battery:

• January bill (inc GST, after DEBS credits): commonly $100–$180
• vs January bill without solar/battery on A1: commonly $350–$500

The difference is the strongest case for solar in WA — Perth's peak summer generation aligns almost perfectly with peak summer demand.

If you're expecting a lower Christmas electricity bill after installing solar this year, upload your Synergy bill to BillWise in January or February to verify the system is performing as expected and compare to your pre-solar consumption.