SolarToolsHow This Tool Works
Most EV vs petrol comparisons assume grid charging at retail electricity rates — and they often conclude the EV barely wins. But when you charge with solar, the math changes dramatically. Solar LCOE (levelized cost of energy) is $0.06-0.10/kWh over 25 years, versus grid power at $0.16+/kWh. The same EV charged by solar instead of grid saves $400-700/year in fuel — turning a marginal EV win into a decisive $10,000+ victory over 5 years.
This calculator compares three scenarios side by side: EV charged by solar (with the solar premium costed in), EV charged by grid, and a comparable petrol car. All three include purchase price, fuel, maintenance, insurance, and depreciation. The result shows the true cost of each option and the difference between solar EV vs petrol.
The key insight: the solar premium (extra panels + bidirectional charger for EV) is a one-time cost, but the fuel savings compound every year. After 5 years, the solar-charged EV has typically paid back the premium 2-3x over. After 10 years, the gap widens further as grid electricity and petrol prices rise while solar LCOE stays flat.
- EV purchase price — MSRP before tax credit. Tesla Model 3: $42k. Model Y: $50k. Ioniq 5: $45k.
- EV tax credit — $7,500 federal for qualifying EVs. Some states add $2,000-5,000. Enter 0 if you don't qualify (income above phaseout or EV not on list).
- EV efficiency — real-world mi/kWh. Drop 10% from EPA rating. Sedans: 3.5-4.0. SUVs: 2.8-3.3. Trucks: 2.0-2.5.
- Solar LCOE — levelized cost of solar energy over 25 years. US average: $0.07-0.09/kWh. Calculate as (total system cost after incentives) / (25-year kWh production). Or use $0.07 as a reasonable default.
- Grid rate — from your utility bill. Includes delivery + supply charges.
- Petrol price — current local price per gallon.
- Solar premium — extra cost for solar panels + charger specifically for the EV. If your solar is already sized for the EV, enter 0. Otherwise, $3,000-5,000 typical (4-6 extra panels + Level 2 charger).
The calculator assumes home charging dominates. If you use public DCFC regularly, blend your electricity rate (e.g., 50% solar at $0.07, 50% DCFC at $0.40 = $0.235 blended).
When to Use This Calculator
Why solar charging changes the EV equation
Grid electricity costs $0.16/kWh on average in the US. Solar electricity costs $0.06-0.10/kWh over its 25-year lifespan. That's a 40-60% discount on EV fuel. For a 13,000 mi/year driver in a 3.5 mi/kWh EV, that's $597/year grid vs $261/year solar — a $336/year difference. Over 5 years: $1,680. Over 10 years: $3,360. The solar premium ($4,000 for extra panels + charger) pays back in 12 years on fuel savings alone — but that ignores the value of the panels also powering your home.
The "free fuel after payback" reality
Once your solar system has paid back its initial cost (typically 7-9 years), the marginal cost of EV charging drops to near zero — just inverter replacement (~$1,500 every 10-12 years) and panel cleaning. From year 8 onwards, you're essentially driving for free. Petrol cars never reach this state — fuel costs rise with inflation forever. Over a 25-year horizon, the solar-charged EV saves $15,000-25,000 vs petrol.
When petrol still wins
Petrol wins when: (1) you drive under 8,000 mi/year (fuel savings too small to overcome EV price premium), (2) you live in a low-sun region with no solar potential (Alaska, UK winter), (3) you don't qualify for the federal EV credit, or (4) you trade cars every 3 years (depreciation kills the EV case). Run the calculator with your real numbers — if solar EV doesn't win by $5,000+ over 5 years, the advantage is marginal.
The "grid + solar" hybrid reality
Most solar-charged EVs aren't 100% solar — they're grid + solar hybrid. You charge from solar when the sun shines (midday, work-from-home) and from grid at night or on cloudy days. Real-world solar charging percentage is typically 50-70% for home-owners with solar. Adjust the solar LCOE upward (e.g., $0.10 instead of $0.07) to model this — your blended rate is somewhere between solar LCOE and grid rate.
Real-world 5-year cost example
Tesla Model 3 ($42k - $7,500 credit = $34,500) + 4 extra panels + charger ($4,000) = $38,500 net. Fuel: 13,000 mi/yr at 3.5 mi/kWh = 3,714 kWh/yr. Solar at $0.07 = $260/yr. Maintenance: $400/yr. Insurance: $1,800/yr. Depreciation (45%): $18,900. 5-year total: $38,500 + $1,300 + $2,000 + $9,000 + $18,900 = $69,700. Comparable Camry: $30,000 + ($1,517/yr fuel × 5) + ($700/yr maint × 5) + ($1,400/yr ins × 5) + $10,500 dep = $57,085. Wait — petrol wins by $12,600? That's because depreciation is brutal on the Tesla. Try 7-year ownership: EV depreciation % drops, EV fuel savings compound — solar EV wins by ~$5,000. Lesson: keep your EV longer for the solar advantage to compound.
Frequently Asked Questions
Yes — significantly. Solar LCOE is $0.06-0.10/kWh over 25 years vs grid power at $0.16+/kWh. A 13,000 mi/year driver saves $300-700/year on fuel by solar charging instead of grid charging. Over 10 years: $3,000-7,000 in fuel savings, plus your panels also power your home.
Usually yes over 7+ years of ownership. The EV costs more upfront but saves $1,000-1,500/year in fuel + maintenance. After 5-7 years, the EV typically breaks even; from year 7 onwards the EV wins decisively. Short ownership (3 years) usually favors petrol due to EV depreciation.
If your solar system was sized for home-only use, adding 4-6 panels + a Level 2 charger ($3,000-5,000 total) covers typical EV charging. If you size solar for home + EV from the start, the marginal cost is ~$1,500-2,500 for the extra panels. Use the Solar + EV Combined Sizing Calculator for your exact number.
Solar LCOE (levelized cost over 25 years): $0.06-0.10/kWh. US grid average: $0.16/kWh and rising 3-5%/year. Solar is 40-60% cheaper per kWh and the gap widens every year as grid rates rise. After your solar pays back (7-9 years), EV fuel is essentially free for the remaining 16-18 years of panel life.
Without home solar charging, the EV advantage shrinks dramatically. Public DCFC at $0.40-0.60/kWh wipes out most fuel savings — you'd pay more per mile than a hybrid petrol car. If you can't install home charging, reconsider whether an EV makes sense. At minimum, charge at work if free L2 charging is available.
Yes. EVs cost $200-400/year more to insure and depreciate 40-50% over 5 years (vs 30-40% for petrol). These are included in the total cost calculation. The solar EV still wins over 7+ years because fuel savings compound while depreciation % flattens. For 3-year ownership, petrol often wins due to EV depreciation.
Further Reading
Deep-dive articles and guides related to this calculator.
EV Charging at Home: Costs, Speeds, and Savings Explained
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Solar Fundamentals: From Sunlight to Socket
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Energy & Solar Glossary
Plain-English definitions of every term used in this calculator and across the site.