Charging your electric car from rooftop solar panels is the cheapest way to drive in Australia — it costs roughly 1–2 cents per kilometre compared to 4–5 cents on the grid and 15–17 cents for petrol. If you already have solar, adding an EV is like getting free fuel. If you're considering solar, an EV dramatically improves the financial case. Here's exactly how much you can save.
Solar vs Grid Charging: Cost Comparison
The economics are simple. Every kWh of solar energy you use to charge your EV is a kWh you don't buy from the grid at 30–35c or export for a meagre 5–10c feed-in tariff. Here's how the numbers stack up:
| Charging Method | Cost per kWh | Cost per 100km | Annual Cost (12,600km) |
|---|---|---|---|
| Petrol (equivalent) | ~19c/km | $17.10 | $2,155 |
| Grid — peak rate | 32c | $5.12 | $645 |
| Grid — off-peak | 19c | $3.04 | $383 |
| Solar (foregone export) | 5–10c | $0.80–$1.60 | $101–$202 |
Annual Savings Breakdown
The savings from solar EV charging are significant and compound across multiple comparisons:
| Comparison | Annual Saving | 10-Year Saving |
|---|---|---|
| Solar EV vs petrol car | $1,950–$2,050 | $22,000–$25,000 |
| Solar EV vs grid-charged EV | $440–$540 | $5,000–$6,500 |
| Solar EV vs off-peak EV | $180–$280 | $2,000–$3,500 |
How Much Solar Excess Do You Need?
The average Australian drives 34.5km per day, which requires about 5.5kWh of electricity. To charge your EV entirely from solar, you need that much excess solar generation each day — energy that would otherwise be exported to the grid.
| Daily Driving | Daily kWh Needed | Solar Excess Required |
|---|---|---|
| 20km (short commute) | 3.2kWh | Low — most systems have this spare |
| 35km (average) | 5.6kWh | Moderate — typical 6.6kW system |
| 50km (longer commute) | 8.0kWh | Higher — may need 8–10kW system |
| 80km (high km driver) | 12.8kWh | Significant — need 10kW+ system |
Check your solar monitoring app to see how much energy you currently export each day. If you're exporting 5–8kWh daily, you likely have enough excess to cover average driving without any changes to your solar system.
Smart Chargers That Divert Solar Excess
The key to maximising solar EV charging is a smart charger that automatically adjusts charging speed to match your available solar surplus. Instead of drawing from the grid when solar drops, the charger throttles down or pauses — and ramps up when sunshine returns.
Zappi (by Myenergi)
The Zappi is the most popular solar-diverting charger in Australia. It monitors your home's energy flow via a CT clamp and has three modes: Eco (solar only), Eco+ (solar with a minimum grid top-up), and Fast (full speed regardless of solar). It works with any inverter brand and any EV. Prices start around $1,200 for the unit.
Tesla Wall Connector
Tesla's Wall Connector integrates with Tesla's solar and Powerwall ecosystem. When configured with a Tesla Gateway or Powerwall, it can prioritise solar charging automatically. It works with non-Tesla EVs too, though solar integration features are best with the full Tesla energy ecosystem.
Fronius Wattpilot
If you have a Fronius inverter, the Wattpilot charger integrates directly via the Fronius ecosystem for seamless solar-diverting. It's a particularly elegant solution if you're installing both a solar system and EV charger at the same time.
Wallbox Pulsar Plus with Solar Integration
The Wallbox Pulsar Plus can integrate with compatible solar inverters and energy management systems to enable solar-prioritised charging. It offers a polished app experience and good scheduling features.
Do You Need a Bigger Solar System?
If you're already exporting 5–8kWh per day, your existing solar system may be sufficient. But if you're considering a new solar installation or an upgrade, here's a rough guide:
- Currently have 5kW solar: You may have 3–5kWh of excess. Enough for short commutes, but consider upgrading to 8–10kW for average driving
- Currently have 6.6kW solar: Typically exports 5–8kWh. Should cover average daily driving in most seasons
- Currently have 10kW+ solar: Likely exports 8–15kWh. Plenty for EV charging plus other household needs
Adding 2–3kW of extra panels specifically for EV charging costs $2,000–$4,000 and can save $500–$800 per year in avoided grid electricity — a payback period of 3–5 years. After that, your EV fuel is essentially free for the remaining 20+ years of panel life.
The Bottom Line
Solar EV charging is the cheapest form of personal transport available in Australia. At 1–2c per kilometre, it's 90% cheaper than petrol and 70% cheaper than grid electricity. If you have solar panels and an EV — or are planning either — the combination delivers savings of $2,000–$3,000 per year compared to a petrol car on grid electricity. That's $20,000–$30,000 over a decade of driving on sunshine.