Electric Vehicles and Off-Grid Solar: Charging Without Grid Power

Off Grid EV Charging with a Tesla Model 3

Electric vehicles EVs are becoming an essential part of modern life, offering a sustainable alternative to fossil fuel transport. For off grid homes and remote locations, integrating EV charging into a standalone solar system can present challenges but it is entirely feasible with careful planning. In this guide, we focus on charging a Tesla Model 3, which typically uses around 8 kWh per day, and explore how to design your off grid solar system to handle EV charging reliably. We cover solar array sizing, battery storage, inverters, load management, and practical tips to future proof your system.

Understanding EV Energy Requirements

The Tesla Model 3 is a popular EV choice for many Australians. On average, it consumes about 8 kWh per day for typical daily driving around 50 to 60 km. However, energy use can fluctuate depending on driving distance, terrain, climate control usage, and seasonal variations.

Key Considerations

• Daily kWh demand 8 kWh per day for typical use
• Battery capacity Model 3 Long Range has 75 kWh usable capacity so occasional long trips can draw more energy
• Charging efficiency EV charging is typically 85 to 90 percent efficient so actual draw from your solar system will be slightly higher than the EV rated consumption

Planning for these requirements ensures your off grid solar system can accommodate EV charging without compromising household power.

Step 1 Solar Array Sizing for EV Charging

Adding an EV to an off grid home increases energy demand. The solar array must be sized to generate enough power to meet household loads and the additional EV consumption.

Calculating Solar Needs

• Daily household consumption assume your home uses 25 to 35 kWh per day
• EV demand add 9 kWh per day for the Tesla Model 3
• Total daily requirement 34 to 44 kWh per day
• Solar production factor in Queensland average solar panel production is about 4 to 5 kWh per kW installed per day

For example, to generate 45 kWh per day

• 45 divided by 4.5 kWh per kW is about 10 kW solar array
• Consider adding 10 to 20 percent extra for cloudy days, system losses, and seasonal variation
• Recommended array size 10 kW. If you are planning weekend trips up to 240 km then you might consider installing up to 15 kW of solar energy and 50 plus kWh of batteries

Tips for EV Integration

• Use high efficiency panels to maximise production in limited space
• Design for expandability add extra panels later if EV use increases or you buy a second EV
• Try to recharge your EV when the battery bank is fully charged such as in the afternoon

Step 2 Battery Storage Considerations

For reliable off grid EV charging, your battery bank must store enough energy for both household loads and EV needs, especially for cloudy days or overnight charging.

Battery Sizing

• Daily energy demand 24 to 29 kWh
• Days of autonomy typically 2 to 3 days for off grid homes
• Depth of discharge DoD for LiFePO4 up to 80 to 90 percent is safe

Example Calculation

• 25 kWh per day × 2 days autonomy = 50 kWh storage
• Accounting for 80 percent usable DoD 50 ÷ 0.8 = 62.5 kWh battery bank

Battery Options

• LiFePO4 batteries are ideal for EV integrated systems due to long cycle life and high DoD
• Modular battery systems allow for future expansion if you upgrade EVs or increase daily driving
• Ensure inverter compatibility with your battery chemistry for seamless charging

Step 3 Inverter Selection and Charging Rate

Your inverter manages the flow of electricity between the solar array, battery bank, household loads, and EV charger. EV charging can put high instantaneous loads on the system, so inverter capacity must be sufficient.

Considerations

• AC charging Tesla Model 3 can charge at up to 7.5 kW with a single phase supply, off grid systems often use 1 phase 5 to 15 kW inverters
• Recommended inverter size for a 10 kW solar array and household loads, a 5 to 10 kW inverter is sufficient for moderate EV charging
• Smart charging use time of use or solar only charging modes to prioritise battery SOC and solar availability

Tips

• Charge EV during peak solar production hours to minimise battery draw
• Consider a dedicated EV inverter charger with load management capabilities

Step 4 Load Management and Smart Control

Off grid systems require careful load management to prevent overloading the inverter or depleting the battery bank.

Strategies

• Time shifting EV charging charge during peak solar production or low household demand
• Automatic load shedding smart inverters can reduce non essential loads if battery SOC drops below a threshold
• Monitoring systems keep track of energy generation, consumption, and EV charging in real time

Step 5 Cabling Safety and Compliance

Integrating EV charging into an off grid system requires proper cabling, breakers, and safety protocols.

Recommendations

• Dedicated EV circuit prevents interference with household loads and ensures safe charging
• Proper cable sizing oversize cables to reduce voltage drop during high current charging
• Compliance follow Australian Standards AS NZS 3000 and 4509 for wiring, isolators, and protection devices
• Surge and fault protection protect both EV and off grid equipment from lightning and electrical faults

Step 6 Future Proofing for Multiple EVs

Many off grid homes plan to add more than one EV. Designing with this in mind saves cost and complexity later.

Considerations

• Oversize solar array and battery bank even if you start with one EV, plan for a second or third vehicle
• Modular inverter setup parallelable inverters allow for increased charging capacity
• Smart load prioritisation EV chargers can share energy dynamically based on battery SOC and solar availability

Step 7 Practical Tips for EV Owners Off Grid

1. Use scheduled charging charge your Tesla Model 3 when solar production is highest
2. Monitor battery SOC avoid deep discharges below 20 percent to protect both your home battery bank and EV
3. Plan for cloudy days keep generator backup or extra battery reserve if you have extended low sun periods
4. Consider solar integrated EV chargers some chargers can dynamically adjust charging rate based on solar availability
5. Keep your system modular allows easy upgrades of panels, batteries, or inverters in the future

Conclusion

Integrating an EV like the Tesla Model 3 into an off grid solar system is entirely feasible with the right planning. By sizing your solar array and battery bank appropriately, selecting the correct inverter, and implementing smart load management, you can charge your EV reliably without grid power. Future proofing your standalone power system ensures it can adapt to increased energy demands, additional EVs, and emerging technologies.

At standalonepower.com.au, we specialise in designing off grid solar systems capable of handling EV charging while maintaining household reliability. Whether you are a remote property owner, homesteader, or environmentally conscious driver, we can create a system that delivers sustainable independent power today and into the future.

Bottom Line

Off grid EV charging requires careful design, but with the right solar array, battery storage, inverter, and load management, your standalone solar system can easily support a Tesla Model 3. Planning for future EVs and energy growth ensures long term reliability.