Charging your electric vehicle with solar in Perth: setup, timing, and savings

An electric vehicle is one of the best investments alongside solar in Perth. A typical EV requires 12–20kWh per 100km. At Synergy's peak rate (55.33c/kWh), that's $6.64–$11.07 per 100km — similar to petrol. But charged from solar generation, the fuel cost drops to near zero. Here's how to set this up properly.

EV electricity cost by charging scenario

| Charging scenario | Electricity cost | Per 100km cost | |---|---|---| | Home A1 tariff, any time | 33.26c/kWh | $4.00–$6.65 | | Midday Saver, peak hours (3–9pm) | 55.33c/kWh | $6.64–$11.07 | | Midday Saver, super off-peak (9am–3pm) | 8.85c/kWh | $1.06–$1.77 | | Solar generation (self-consumption) | ~0c/kWh | ~$0 |

The difference between peak charging (55c/kWh) and solar charging (0c/kWh) on a Midday Saver tariff is dramatic. Timing your EV charging correctly is the most important factor.

What home EV charger do you need?

Level 1 (standard wall outlet, 10A):

• Provides approximately 2.4kW charge rate
• Charges at approximately 8–10km of range per hour
• Adequate for low-mileage drivers (< 60km/day) if charged overnight
• No installation cost (uses existing power points)

Level 2 (dedicated EV charger, 7.4kW single-phase or 22kW three-phase):

• Single-phase 7.4kW: approximately 45–50km of range per hour
• Three-phase 22kW: approximately 130km of range per hour (requires three-phase power)
• Installation cost: $900–$2,000 for the charger plus installation in Perth (2026 pricing)

For solar optimisation, a 7.4kW single-phase charger is the most useful: it draws at or below peak solar generation from a 6.6kW+ system, making it possible to charge entirely from solar during midday generation hours.

Scheduling EV charging around solar

The ideal schedule for Perth on Midday Saver:

• Set the EV charger to start at 9am (Midday Saver super off-peak begins)
• Set a stop time at 3pm (before peak rate begins)
• This 6-hour window at 7.4kW provides approximately 44kWh of charge — enough for 220–350km of range in most EVs
• During this window, your solar system is also at peak generation

Most EVs support scheduled charging via the car's own app (set the car's departure time). Some smart chargers (Zappi, Fronius Wattpilot, Wallbox) also support direct solar-diversion mode — the charger automatically matches charge rate to available solar surplus.

Solar-diverting EV chargers

A standard EV charger draws at its set rate (e.g. 7.4kW) regardless of whether solar is generating. A solar-diverting charger (also called an eco-mode or green-mode charger) adjusts its charge rate in real time to match solar surplus:

How it works: The charger monitors grid import/export. When solar surplus increases, it increases charge rate; when surplus drops, it reduces charge rate. The EV charges from the available surplus at all times, with minimal grid import.

Popular models in Perth:

• Zappi (myenergi): popular solar-diverting charger, adjustable minimum charge current
• Fronius Wattpilot: integrates tightly with Fronius inverters
• Wallbox Pulsar Plus: smart charging with app control

Consideration: Most EVs have a minimum charging current (typically 6A = 1.4kW). Below this threshold, the charger can't reduce the draw further — it will either stop charging or draw a minimum 1.4kW from the grid. For very small solar surpluses (e.g. cloudy day), the diverter may pause charging repeatedly rather than providing slow continuous charge.

Sizing solar for EV charging

Adding an EV meaningfully increases your electricity consumption. A 15,000km/year driver at 15kWh/100km needs 2,250kWh/year of additional electricity — about 6.2kWh/day.

Additional solar capacity needed: At Perth's 5 peak solar hours per day, generating an additional 6.2kWh/day requires approximately 1.5–1.8kW of additional solar capacity (accounting for system efficiency losses):

• A small 2kW add-on to your existing system would cover EV charging
• Or a system upgrade from 6.6kW to 8–10kW

If you're installing solar and an EV simultaneously, size the system to cover both household consumption and EV charging. A 10–13kW system is well-matched for a Perth household with an EV.

Midday Saver vs A1 for EV owners

For EV owners who can charge during the day (work from home, part-time workers, retirees), Midday Saver's 8.85c/kWh super off-peak rate provides an excellent EV charging cost even without solar — $1.06–$1.77 per 100km from the grid during 9am–3pm.

For EV owners who must charge at night (typical commuter), Midday Saver's 55.33c/kWh peak rate from 3pm–9pm is a trap: plugging in as soon as you get home from work (3–7pm) incurs peak charges. On Midday Saver, use a scheduled charge start after 9pm (off-peak resumes) or delay until the following morning's super off-peak window.

A1 tariff for night-chargers: The flat A1 tariff (33.26c/kWh) is simpler for commuters who charge at night and don't have solar. At 33c, EV charging costs $4–6.65 per 100km — less than petrol but not as cheap as solar-charged options.

Battery and EV: the storage-to-vehicle approach

A home battery can store solar generation during the day and discharge it for EV charging in the evening. This is useful for:

• Commuters who come home after 3pm (Midday Saver peak) and need to charge overnight
• The battery charges during solar generation hours, discharges to power the charger from 9pm–7am (off-peak)

Caveat: EV charging draws 7.4kW (single-phase), and a 10kWh battery discharges in approximately 80 minutes at this rate. For full EV charging from a home battery, you'd need a 20–40kWh battery system — well beyond standard residential battery sizes. More practical: use the battery to cover other household loads in the evening and charge the EV directly from the grid's off-peak rate (or from super off-peak the following morning).

EV range and charging rates vary by vehicle. Check your specific EV's onboard charger capacity — many EVs are limited to 7.4kW single-phase even with a higher-rated charger installed.