Electric Car Running Costs: How Much Cheaper with Solar?

Switching from a petrol car to an electric vehicle is a big financial decision. The purchase price is higher, but the running costs are dramatically lower. Add solar power, and the maths becomes compelling. A solar carport with EV charging can reduce your car's running costs to almost nothing.

Let's break down the real numbers: cost per mile for petrol cars, grid-charged EVs, and solar-charged EVs. Then we'll explore how much you actually save over a year and how solar carports impact payback periods.

Cost Per Mile: Petrol vs EV vs Solar EV

This is the figure that matters most to drivers. Here are realistic 2026 UK costs:

The difference is staggering. A solar-charged EV costs roughly one-hundredth the price to run compared to a petrol car.

Breaking Down the Real-World Scenario

Let's model a realistic UK household driving 12,000 miles per year (slightly above average):

Petrol Car (e.g., Ford Focus)

• Annual miles: 12,000
• Fuel efficiency: 45 mpg (combined)
• Annual fuel consumption: 267 litres
• Petrol price (average): £1.35/litre
• Annual fuel cost: £360

Grid-Charged EV (e.g., Volkswagen ID.4)

• Annual miles: 12,000
• EV efficiency: 3.5 miles/kWh
• Annual electricity consumption: 3,429 kWh
• Grid electricity price (average): 28p/kWh
• Annual electricity cost: £960

Wait—grid charging costs more than petrol running costs in this scenario! This is true for many UK drivers on standard tariffs. The EV advantage erodes if you're on a high-cost tariff and can't shift charging to off-peak hours.

Solar-Charged EV (with 6kW Solar Carport)

• Annual miles: 12,000
• EV efficiency: 3.5 miles/kWh
• Annual electricity consumption: 3,429 kWh
• Solar generation (6kW system, Midlands): ~5,200 kWh/year
• Percentage of EV charging from solar: ~85%
• Grid electricity required: 514 kWh/year
• Grid electricity cost (at 28p/kWh): £144
• Total annual EV charging cost: £144

With solar, you're essentially charging your car for free, with grid electricity as backup on cloudy days or winter evenings.

Annual Fuel Savings: The Comparison

For a 12,000 mile annual driver:

A solar carport adds £716-£916 per year in fuel savings compared to charging from the grid. That's a tangible financial benefit beyond the environmental advantage.

Real-World Scenarios: Different Mileages

Fuel savings scale with mileage. Here's how different annual drive distances affect total savings:

Low Mileage: 8,000 Miles/Year

• Petrol annual cost: £1,080
• Grid EV annual cost: £640
• Solar EV annual cost: £96
• Annual solar advantage over grid: £544

Medium Mileage: 12,000 Miles/Year

• Petrol annual cost: £1,620
• Grid EV annual cost: £960
• Solar EV annual cost: £144
• Annual solar advantage over grid: £816

High Mileage: 20,000 Miles/Year

• Petrol annual cost: £2,700
• Grid EV annual cost: £1,600
• Solar EV annual cost: £240
• Annual solar advantage over grid: £1,360

For high-mileage drivers, solar charging adds significant value. A company car doing 20,000 miles yearly saves £1,360 per year on fuel—enough to offset battery storage costs.

Battery Storage Impact on EV Charging

Adding a home battery (like a 9.5kWh GivEnergy or 10kWh SolarEdge) changes the maths further. Instead of exporting unused solar to the grid, you store it for evening charging:

Without Battery Storage

• Solar carport generates 5,200 kWh/year
• EV consumes 3,429 kWh/year (for 12,000 miles)
• Daytime solar EV charging: ~3,000 kWh (if car is parked during generation)
• Home consumption: ~3,500 kWh/year (typical)
• Excess solar exported to grid: ~699 kWh/year (at £0.15/kWh = £105 SEG income)
• Grid electricity needed for evening EV charging: ~429 kWh/year (£120)
• Net EV charging cost: £15

With 9.5kWh Battery Storage

• Solar carport generates 5,200 kWh/year
• Daytime solar charges car directly: ~2,500 kWh (limited by parking time)
• Excess solar charges battery: ~2,000 kWh
• Battery supplies evening EV charging: ~929 kWh (from stored solar)
• Grid electricity needed: 0 kWh for EV charging
• Home consumption covered by battery + solar: ~5,200 kWh
• Grid electricity needed for home only: ~100 kWh/year (£28)
• Net EV charging cost: -£28 (you're actually saving money)

With battery storage, you can charge your car almost entirely on solar power, even when you charge in the evening. This is the real game-changer for EV owners.

Payback Analysis: Carport + Battery + EV Charging

Here's the full financial picture for a 3-bay solar carport with battery storage and EV charging:

Annual savings (assuming switch from petrol car + grid charging):

• EV fuel savings vs petrol: £1,476
• Home electricity savings (battery + solar): £600-£800
• Total annual savings: £2,076-£2,276
• Payback period: 25-27 years

This sounds long, but consider:

• Structural lifespan: Oak frame carports last 50+ years
• Component warranties: 10-year guarantee on structure, 15+ years on solar tiles
• Zero depreciation after payback: Then it's pure savings for another 25 years
• Property value addition: A premium oak carport + solar system typically adds £30,000-£40,000 to home value
• Avoided inflation: Fuel prices historically rise faster than utility costs. Petrol at £2.00/litre would give you £2,700/year EV advantage

If you're planning to stay in your home for 10+ years, the economics are strong. If you sell before payback, you recoup much of the investment through increased property value.

Combining Car Savings with Household Savings

The real value of a solar carport emerges when you calculate total household benefits, not just EV charging:

Annual Savings Across All Sources

• EV charging vs petrol car: £1,476/year
• Home electricity (solar + battery): £600-£900/year
• Smart Export Guarantee (SEG) income: £50-£200/year (if excess generation)
• Maintenance savings (EV vs petrol): £450-£600/year (no oil changes, less brake wear)
• Total annual household savings: £2,576-£3,176/year

With £2,800/year in combined savings, your £56,905 system pays for itself in 20 years—but you've also upgraded your home's value by £30,000+ and eliminated almost all fuel costs.

Impact of Smart Charging and Tariffs

Grid electricity pricing is changing. Time-of-use tariffs like Octopus Go offer 7p/kWh off-peak (typically 11pm-7am). If you charge your EV overnight on a cheap tariff, grid charging becomes even more competitive:

The emergence of cheap off-peak tariffs changes the equation slightly. However, solar carports still provide maximum value because:

• Solar generation is free once installed (no fuel price risk)
• Battery storage lets you use solar even at night (matching smart tariff benefits)
• Household daytime demand is often high (working from home, charging)
• You're not dependent on your utility's tariff pricing strategy

The Bigger Picture: Why Solar EVs Make Sense

The cost-per-mile numbers are compelling, but there's more to the story:

• Energy independence: You generate your own fuel, immune from fuel price spikes
• Carbon footprint: A solar-charged EV produces 95% fewer emissions than a petrol car
• Home resilience: With battery storage, you have backup power during grid outages
• Property premium: Buyers pay more for homes with integrated solar and EV charging
• Depreciation safety: Even if panel efficiency drops 0.5%/year, you're still saving money
• Future-proofing: As the grid decarbonizes, your solar system becomes even more valuable

Real-World Example: The Complete Picture

Sarah, a UK homeowner, switches from a petrol Honda Civic to a Tesla Model 3 and installs a solar carport:

• Petrol car annual cost (12,000 miles): £1,620 fuel + £700 maintenance = £2,320
• Grid-charged EV cost: £960 electricity + £200 maintenance = £1,160
• Solar-charged EV cost (with battery): £50 grid electricity + £200 maintenance = £250
• Annual fuel savings vs petrol: £2,070
• Annual savings vs grid EV: £910

After 25 years:

• Petrol car total cost: £58,000 (fuel + maintenance + car depreciation)
• Grid EV total cost: £42,000
• Solar EV total cost: £56,905 (system) + £6,250 (maintenance) = £63,155, but she's now driven 2+ cars entirely on solar and owns a £35,000+ property upgrade

The math heavily favours solar, especially if you value energy independence and long-term wealth building alongside carbon reduction.