Charging your EV with solar power sounds simple — plug in when the sun is shining. In practice, there are several approaches, each with different trade-offs between convenience, cost, and how much solar energy you actually capture. This guide covers the three main methods and practical tips for maximising your solar EV charging throughout the year.
Option 1: Timer-Based Charging (Simple and Free)
The simplest approach requires no additional equipment. You set your EV or charger to charge during the peak solar generation hours — typically 9am to 3pm — and your solar panels do the rest.
How to Set It Up
- Check your solar monitoring app to identify your peak generation window (usually 9am–3pm)
- Set your EV's scheduled charging to start at 9am or 10am
- Set it to stop by 3pm or 4pm (or let it complete naturally)
- Plug your car in before bed or when you arrive home — it won't start until the scheduled window
Pros and Cons
- Pro: Free — no extra hardware needed beyond your existing charger
- Pro: Easy to set up on most EVs
- Con: No adjustment for cloud cover — the car draws a fixed rate regardless of solar availability
- Con: May draw from the grid if solar generation drops below charging demand
- Con: Requires the car to be home during the day
Option 2: Smart Charger with Solar Diversion (Recommended)
A smart charger with solar diversion is the gold standard for solar EV charging. It monitors your household energy flow in real time and adjusts charging speed to match your available solar excess — ramping up when the sun is strong and throttling down or pausing when clouds pass over. See our roundup of the best EV chargers for solar in Australia for specific model recommendations.
How It Works
A current transformer (CT) clamp is installed on your main supply cable at the switchboard. The smart charger reads this signal to determine how much power is being exported to the grid. It then adjusts the EV charging rate to absorb as much of that export as possible without drawing from the grid.
Popular Solar-Diverting Chargers
| Charger | Solar Diversion Mode | Min. Diversion Power | Price (unit) |
|---|---|---|---|
| Zappi V2 | Eco / Eco+ modes | 1.4kW (6A single phase) | $1,200–$1,600 |
| Tesla Wall Connector | Via Powerwall / Gateway | Varies | $800–$1,000 |
| Fronius Wattpilot | Eco mode (Fronius inverters) | 1.4kW | $1,100–$1,500 |
| Wallbox Pulsar Plus | Via energy management system | 1.4kW | $900–$1,200 |
| EVSE DIN Rail + Solar | Via external CT monitoring | 1.4kW | $800–$1,100 |
Pros and Cons
- Pro: Maximises solar self-consumption — typically 80–95% solar charging on sunny days
- Pro: Fully automatic — set and forget
- Pro: Works with variable cloud conditions
- Con: Higher upfront cost ($300–$600 more than a basic charger)
- Con: Minimum charging threshold of ~1.4kW means it can't divert very small solar surpluses
Option 3: Home Battery as Buffer
If you have a home battery (like a Tesla Powerwall or BYD HVS), you can use it as a buffer — the battery charges from solar during the day and then the EV charges from the battery overnight.
How It Works
- Solar charges the home battery during peak generation hours
- In the evening, the battery powers your household and EV charger
- The EV effectively charges from stored solar energy
Pros and Cons
- Pro: Charge your EV from solar energy at any time — day or night
- Pro: Car doesn't need to be home during the day
- Pro: Battery also provides backup power and evening solar usage
- Con: Expensive — home batteries cost $8,000–$15,000
- Con: Energy loss through battery round-trip efficiency (~10–15%)
- Con: Battery capacity may not cover both home and EV charging needs
This approach is best suited for households that already have or are planning a home battery for other reasons (backup power, evening self-consumption). It's generally not cost-effective to buy a home battery solely for EV charging — a smart charger is a far cheaper solution.
Practical Tips for Maximising Solar EV Charging
1. Charge During Peak Solar Hours
Solar generation peaks between 10am and 2pm. If possible, ensure your EV is plugged in and charging during this window. Even with a smart charger, having the car available during peak hours maximises solar capture.
2. Reduce Other Daytime Loads
When your EV is charging from solar, avoid running other heavy appliances (pool pump, ducted air conditioning, oven) simultaneously. Schedule these outside the EV charging window to maximise the solar energy available for your car.
3. Pre-Condition Your EV on Solar
Most EVs can pre-heat or pre-cool the cabin while plugged in. Do this during solar hours and the energy comes from your panels rather than the battery, preserving range.
4. Don't Aim for 100% Solar
Trying to charge exclusively from solar can be impractical, especially in winter. A realistic target is 60–70% solar charging over a year, supplemented by off-peak grid charging when needed. This still delivers enormous savings.
What to Do on Cloudy Days
Cloudy days are inevitable, especially in southern states during winter. Here's how to handle them:
- Smart charger Eco+ mode: Allows minimum grid charging when solar is insufficient
- Off-peak fallback: Set your car to charge overnight at off-peak rates if it didn't get enough solar during the day
- Don't stress about it: Even at off-peak grid rates (18–22c/kWh), charging is far cheaper than petrol. Solar charging is the ideal, not the requirement
- Use your buffer: If you only drive 30–40km per day, a partially charged battery from a cloudy day still covers your needs
The best approach combines a smart charger for daytime solar diversion with scheduled off-peak charging as a backup. This way, you maximise solar use on sunny days while ensuring your EV is always ready to go — regardless of the weather.