If you own or are considering an electric vehicle, one of the most powerful combinations available to Australian homeowners is charging your EV from solar panels. But how much solar do you actually need to fully cover your EV's charging requirements? The answer depends on your driving distance, your EV's efficiency, and how much solar generation you can reliably count on in your location — and the maths is surprisingly straightforward.
How Much Energy Does Your EV Need Each Day?
To determine how much solar you need, start with your daily driving distance and your EV's energy consumption (kWh per 100km). The average Australian driver travels approximately 35–50km per day, but this varies widely between city commuters and regional drivers.
| Daily Driving Distance | Energy Needed (15 kWh/100km EV) | Energy Needed (18 kWh/100km EV) |
|---|---|---|
| 30km/day (urban commuter) | 4.5 kWh | 5.4 kWh |
| 50km/day (average driver) | 7.5 kWh | 9.0 kWh |
| 80km/day (high mileage) | 12.0 kWh | 14.4 kWh |
| 120km/day (regional/heavy user) | 18.0 kWh | 21.6 kWh |
A typical 50km/day driver in a mid-size EV needs roughly 7–9 kWh of electricity per day for charging. This is the target your solar system needs to cover — at least on an average day.
How Much Solar Generation Can You Count On?
Solar generation is measured in peak sun hours — a standardised way of expressing how much energy a 1kW solar panel generates per day on average in your location. In Australia, this ranges from about 3.5 peak sun hours in Hobart to 5.5+ in Darwin and Broome.
| City | Avg Daily Peak Sun Hours | Output from 1kW of Solar (kWh/day) | Output from 6.6kW System (kWh/day) |
|---|---|---|---|
| Brisbane | 4.9 | 4.2 kWh | 27.5 kWh |
| Sydney | 4.6 | 4.0 kWh | 26.2 kWh |
| Perth | 5.1 | 4.4 kWh | 29.0 kWh |
| Melbourne | 4.0 | 3.5 kWh | 23.0 kWh |
| Adelaide | 4.8 | 4.2 kWh | 27.5 kWh |
| Hobart | 3.5 | 3.1 kWh | 20.3 kWh |
| Darwin | 5.5 | 4.8 kWh | 31.7 kWh |
How Much Extra Solar Capacity Does an EV Add?
The key insight is that your EV's charging needs stack on top of your existing household electricity consumption. If your home already uses 20 kWh/day and your EV needs an additional 7.5 kWh/day, your total daily demand is 27.5 kWh. A 6.6kW solar system in Brisbane generates approximately 27.5 kWh/day on average — so a 6.6kW system could theoretically cover both your home and EV.
As a rule of thumb, each 10km of daily driving requires roughly 0.3–0.4kW of additional solar capacity. Here's a more detailed guide:
| Daily Driving Distance | Additional Solar Needed (Brisbane/Sydney) | Additional Solar Needed (Melbourne/Hobart) |
|---|---|---|
| 30km | +1.1–1.4 kW | +1.5–2.0 kW |
| 50km | +1.8–2.2 kW | +2.5–3.0 kW |
| 80km | +2.9–3.6 kW | +3.9–4.8 kW |
| 120km | +4.3–5.4 kW | +5.8–7.2 kW |
The Importance of Timing: Daytime Charging
The maths only works if you can charge during the solar generation window — typically 9am to 3pm. For working households where the car leaves before solar peaks, daytime solar-powered EV charging requires one of the following solutions:
- Work from home: The car stays home during peak solar hours and can charge directly from solar surplus.
- Smart EV charger with solar integration: Chargers from Zappi, myenergi, and some Wallbox models detect excess solar export and divert it to the EV automatically — even when you're at work, as long as the car is plugged in.
- Home battery as a buffer: Store daytime solar in a battery, then charge the EV from the battery in the evening. This adds significant cost but maximises solar utilisation.
- EV as overnight charger on off-peak: If daytime solar capture isn't practical, off-peak overnight charging at 14–18c/kWh is still very cheap, even if it's not solar.
Seasonal Variation: The Winter Problem
Solar generation drops significantly in winter, particularly in Victoria, Tasmania, and the ACT. A system that comfortably covers your EV charging in summer may fall short by 30–40% in the depths of winter. This is where sizing your system slightly larger than the summer average makes sense — or accepting that you'll supplement with grid power in winter months.
In Queensland and WA, seasonal variation is much less pronounced. Solar generation in winter is still 70–80% of summer output, making year-round solar EV coverage much more reliable.
The Combined Financial Case
Solar-powered EV charging is the most economical way to drive in Australia. Consider the numbers for a 50km/day driver in Sydney with a Tesla Model 3:
- EV charging cost on grid: ~$4.80/100km × 18,000km/year = $864/year
- EV charging cost on solar: ~$0.50/100km equivalent × 18,000km/year = $90/year
- Solar EV saving: ~$774/year in charging costs alone
An extra 2kW of solar panels (to cover the EV's energy needs) costs approximately $1,500–$2,000 installed — paying back in 2–3 years from charging savings alone.
Calculate Your Solar + EV System Size
Ready to find out exactly how much solar you need to fully cover your EV and household energy needs? Use our Solar + EV Synergy Calculator to enter your driving distance, EV model, household consumption, and location — and get a personalised recommendation for the solar system size that maximises your combined savings.