Combining solar panels with electric vehicle charging creates a powerful synergy where you’re powering your car directly from sunshine instead of gasoline or grid electricity. This guide explains how solar EV charging works, what system size you need, how to optimize charging schedules, and the financial and environmental benefits of this increasingly popular combination.
THE SOLAR + EV SYNERGY
Electric vehicles represent the biggest opportunity most households have to increase electricity consumption meaningfully. Where adding appliances might add 50-100 kWh monthly, EVs can add 400-800 kWh monthly depending on driving habits.
Typical EV Consumption:
Average driving: 12,000 miles yearly Average EV efficiency: 3 miles/kWh Annual electricity needed: 4,000 kWh Monthly electricity: 333 kWh
Put in perspective:
- Average home electricity: 900 kWh/month
- Adding an EV: Increases to 1,233 kWh/month (37% increase)
This dramatic consumption increase means your solar system can be sized larger, improving economics through better equipment pricing and maximizing your roof’s potential.
The Gasoline Comparison:
12,000 miles yearly in gas car (30 MPG): 400 gallons At $3.50/gallon: $1,400 annual fuel cost
Same driving in EV charged from grid: 4,000 kWh at $0.13/kWh: $520 annual cost Annual savings vs gas: $880
Same driving in EV charged from solar: 4,000 kWh solar cost: $0 (after system pays off) Annual savings vs gas: $1,400 30-year savings vs gas: $42,000
Environmental Impact:
Gas car (12,000 miles, 30 MPG): 11,000 lbs CO2 annually
EV charged from grid: 4,000-7,000 lbs CO2 (varies by grid source)
EV charged from solar: 0 lbs CO2 during operation
SIZING YOUR SOLAR SYSTEM FOR EV CHARGING
Adding EV charging to your solar planning requires calculating additional capacity needed beyond home usage.
Step-by-Step Sizing:
1. Calculate Current Home Usage
Review 12 months of utility bills:
- Total annual consumption: 10,800 kWh
- Monthly average: 900 kWh
- System size needed: 7-8 kW (produces ~900 kWh/month)
2. Calculate EV Charging Needs
Determine your typical driving:
- Daily miles: 35 miles
- EV efficiency: 3 miles/kWh
- Daily electricity needed: 12 kWh
- Monthly EV consumption: 360 kWh
3. Calculate Total System Size
Home usage: 900 kWh/month (7-8 kW system) EV charging: 360 kWh/month (3 kW additional) Total needed: 1,260 kWh/month (10-11 kW system)
Real Example Calculation:
The Martinez family drives 40 miles daily in their Tesla Model 3 (4 miles/kWh efficiency):
- Daily EV consumption: 10 kWh
- Monthly: 300 kWh
- Their home uses 850 kWh monthly
- Total system sized: 10.5 kW (produces ~1,150 kWh monthly)
This system covers both home usage and EV charging with slight surplus for less-than-ideal weather conditions.
