Solar panels and electric cars are each excellent money savers on their own. Together, they create something even more powerful — a feedback loop where solar dramatically reduces both your household electricity bill and your transport fuel costs simultaneously. For a typical Australian family, the combined savings can reach $3,000–$5,000 per year. Here's how the synergy works.
The Combined Savings Potential
To understand the full picture, let's look at what each component saves individually and then together:
| Scenario | Annual Electricity Cost | Annual Fuel Cost | Total Energy Cost |
|---|---|---|---|
| No solar + petrol car | $2,400 | $2,155 | $4,555 |
| Solar + petrol car | $800 | $2,155 | $2,955 |
| No solar + EV (grid) | $2,400 | $645 | $3,045 |
| Solar + EV (solar charged) | $500 | $161 | $661 |
How the Synergy Works
Solar panels and EVs amplify each other's value in several key ways:
1. Solar Covers Both Home and Transport Energy
A typical Australian household uses about 18–20kWh of electricity per day. A 6.6kW solar system generates roughly 24–28kWh per day in most Australian climates. Without an EV, much of the excess is exported to the grid for a meagre 5–10c/kWh feed-in tariff. An EV absorbs that excess productively — effectively converting surplus sunshine into free fuel worth 30c+/kWh in avoided grid electricity or $1.90/L in avoided petrol.
2. EV Charging Increases Solar Self-Consumption
The biggest weakness of solar-only systems is low self-consumption — many households only use 30–40% of their solar generation directly. Adding EV charging during daylight hours can push self-consumption to 60–80%, dramatically improving the return on your solar investment.
3. Falling Feed-In Tariffs Make Self-Consumption More Valuable
As feed-in tariffs continue to fall (now typically 5–8c/kWh in most states), the value of exporting solar energy decreases. Using that energy to charge an EV instead gives it a value of 30c+/kWh (avoided grid cost) or 19c/km (avoided petrol cost). Your solar energy is worth 3–6 times more when used to charge your car than when exported.
Case Study: Typical Australian Family
Let's follow the Nguyen family in suburban Brisbane. They have a 6.6kW solar system and recently replaced their second car with a BYD Dolphin.
Before EV (Solar + Petrol Car)
| Cost Item | Annual Cost |
|---|---|
| Grid electricity (after solar offset) | $900 |
| Solar export income | –$350 |
| Petrol (12,600km @ 9L/100km) | $2,155 |
| Petrol car servicing | $800 |
| Total annual cost | $3,505 |
After EV (Solar + BYD Dolphin)
| Cost Item | Annual Cost |
|---|---|
| Grid electricity (after solar offset) | $650 |
| Solar export income (reduced — more used by EV) | –$180 |
| EV charging (70% solar, 30% off-peak grid) | $195 |
| EV servicing | $300 |
| Total annual cost | $965 |
The Multiplier Effect on Solar ROI
Adding an EV to a solar household doesn't just save on fuel — it improves the return on investment of the solar system itself. Here's why:
| Metric | Solar Only | Solar + EV |
|---|---|---|
| Self-consumption rate | 30–40% | 60–80% |
| Value per kWh generated | 15–20c (blended) | 22–28c (blended) |
| Annual solar savings | $1,200–$1,600 | $2,000–$2,800 |
| Solar payback period | 4–6 years | 3–4 years |
By increasing self-consumption, an EV effectively shortens your solar payback period by 1–2 years and increases the total lifetime value of your solar system by $15,000–$25,000.
Is It Worth Getting Solar Just for EV Charging?
If you already have an EV and don't have solar, the answer is almost certainly yes. A 6.6kW solar system costing $6,000–$8,000 will:
- Reduce your household electricity bill by $1,200–$1,600 per year
- Reduce your EV charging cost by an additional $400–$600 per year
- Total savings of $1,600–$2,200 per year
- Payback period of 3–4 years
- Then 20+ years of near-free electricity and fuel
Getting Started
If you're considering the solar + EV combination:
- Already have solar? Check your export data. If you're exporting 5+ kWh per day, an EV will put that energy to much better use
- Already have an EV? Solar panels will dramatically reduce your charging costs. Size your system to cover both home and EV energy needs
- Have neither? Consider getting both. The combined savings make the investment case stronger than either alone
- Install a smart charger like the Zappi to maximise solar EV charging automatically
The solar + EV combination is the most powerful household energy saving strategy available to Australian families today. With combined savings of $3,000–$5,000 per year and payback periods of 3–5 years, it's an investment that pays for itself many times over.