Understanding your household energy profile in Perth: when you use electricity and why it matters

Two households with identical annual electricity consumption can have completely different solar economics — because one household uses most of their electricity during the day, and the other uses it in the evenings. Understanding when your household draws power is the foundation for solar sizing, tariff selection, and battery decisions.

What is an energy usage profile?

Your energy profile shows how much electricity you use at different times of day, different days of the week, and different seasons. A smart meter records this in 30-minute intervals (interval data).

High morning usage profile: Household with early risers — hot water, cooking, laundry in the morning. If the hot water system is electric and runs in the morning, this creates a significant pre-solar-generation demand.

Daytime-absent profile: No one home 8am–5pm. Low daytime usage. Evening peak when the household returns. This profile benefits significantly from solar (daytime exports reduce bills) but the self-consumption rate is lower.

Evening-heavy profile: WFH household or family home where most electricity is used between 6pm–10pm. Solar self-consumption is limited to shared household loads during the day; evening demand is met from the grid.

Always-on base load: A household with a pool pump running all day, or multiple fridges, has a higher base load that solar consistently offsets. These households often have high solar self-consumption rates.

How to access your interval data

Via Synergy: Log into MyAccount on the Synergy website. Under "Your electricity," you can request interval data (half-hourly readings from your smart meter) in CSV format. This covers the most recent 12 months.

Via BillWise: If you've uploaded your bills to BillWise, the analysis provides a simplified view of your usage pattern based on your billing data and tariff structure.

Reading the data: Interval data shows consumption (kWh imported from grid) per 30-minute period. For solar customers, it also shows exports per period. Note: interval data shows grid flows, not total consumption — self-consumed solar isn't captured in the import/export data (it's consumed at the meter, not recorded by it).

What your profile reveals about solar sizing

Daytime base load: The amount you consume during solar generation hours (roughly 9am–3pm) sets the floor on useful self-consumption from solar. If your daytime base load is 0.5kW (12kWh over 24 hours but concentrated in non-solar hours), a large solar system will export most of its generation.

Peak load timing: If your peak consumption is 6pm–10pm, solar can't directly offset it (generation has ended). A battery bridges this — charging from daytime solar and discharging in the evening peak.

Hot water system timing: If your hot water system runs on an off-peak timer (typically 11pm–7am) or a standard element (which often runs in the morning), it may represent 4–8kWh/day of consumption that solar doesn't directly offset. A solar diverter (hot water timer reconfigured to run during solar generation hours) or heat pump hot water system can capture this demand with solar self-consumption.

Typical Perth household profiles

Single person, WFH:

• Daytime load: 0.8–1.5kW (computer, monitor, occasional appliances)
• Evening load: 0.5–1.5kW (cooking, TV, AC)
• Self-consumption potential from solar: high (home during solar hours)
• Battery benefit: moderate (evening load moderate)

Two-income household, no one home 9–5:

• Daytime load: 0.2–0.4kW (fridge, standby)
• Evening load: 1.5–4kW (cooking, AC, multiple people)
• Self-consumption potential from solar: low (nobody home)
• Battery benefit: high (captures solar for evening peak)

Family home, school-aged children:

• Daytime load: 0.3–0.6kW (fridge, standby)
• After-school/evening: 2–5kW (multiple appliances, AC, cooking)
• Weekend daytime: 1–3kW
• Battery benefit: high on weekdays, lower on weekends

Retirees at home:

• Daytime load: 1–3kW (variable appliances, AC, cooking at lunch)
• Evening load: 0.8–2kW
• Self-consumption potential: very high
• Battery benefit: moderate to low (high self-consumption without it)

Using your profile for tariff selection

A1 (flat rate, 33.26c/kWh) is better if:

• Your consumption is spread throughout the day and evening
• You can't shift loads to specific time windows
• Your solar self-consumption rate is already high (you're already avoiding most peak-rate imports)

Midday Saver is better if:

• You have significant flexible loads you can shift to 9am–3pm (off-peak at 8.85c)
• Your dishwasher, laundry, and hot water can run during the day
• Your evening imports are modest

Your energy profile helps you calculate the tariff savings: If your interval data shows you currently import 2kWh between 9am–3pm and 4kWh between 3pm–9pm, you can model the Midday Saver vs A1 cost directly.

Using your profile for battery sizing

Evening demand = primary battery sizing input: The number of kWh you import from the grid between 5pm and 11pm is approximately how large a battery you need to avoid all evening grid imports.

Example: Interval data shows 6kWh of grid imports between 5pm–11pm on a typical weekday. A 10kWh battery (8.6kWh usable) comfortably covers this. A 5kWh battery covers it partially.

Avoid over-sizing based on solar generation: A battery sized to store all your solar exports may be far larger than needed to cover evening demand. The economic case is based on what you actually consume in the evening from the grid — not what you generate.

Seasonal variation in Perth

Perth's energy profile shifts significantly between summer and winter:

Summer:

• High AC use (evening and nighttime)
• Solar generation at maximum (30–36kWh/day from 6.6kW system)
• Frequent high self-consumption during the day
• High evening imports for AC if no battery

Winter:

• Low AC use
• Solar generation at minimum (11–15kWh/day from 6.6kW system)
• Hot water and heating may increase morning imports
• Bill savings from solar substantially lower

Understanding your seasonal profile helps set realistic expectations for annual savings from solar and battery.

Your interval data is the most useful single source of information for solar and battery planning. If you haven't downloaded it from Synergy MyAccount, it's worth 10 minutes — the half-hourly consumption data for a full year answers the questions that generalised solar calculators can't.