EV Charging Calculator

How much does it cost to charge your EV, and how many solar panels does it take to cover it?

EV details

EV battery size?

kWh

Daily miles driven?

miles/day

Efficiency?

mi/kWh

Charger level?

Cost & solar

Electricity rate?

$/kWh

Peak sun hours?

hrs/day

Existing solar (if any)?

EV charging energy & solar needs

11.43 kWh/day for EV · $51.43/month

Monthly EV kWh343 kWh

Cost per mile (electric)$0.043/mile

Daily charge time1.5 hrs/day

Full charge time9.7 hrs (0-100%)

vs. gas (30 mpg, $3.50)Save $89/mo

To fully power your EV with solar: add 3.0 kW (8 × 400W panels) to your system. At $51.43/month charging cost, the additional solar pays back in approximately 10.9 years.

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How to Use This Calculator

Enter your EV and driving details

The three key numbers are battery size (kWh), daily miles driven, and efficiency (mi/kWh). Daily miles drives how much you actually need to charge each day — a 60 kWh battery doesn't need to be charged from 0% every night if you only drive 30 miles. Efficiency varies significantly: sporty driving reduces it, highway speeds reduce it, cold weather reduces it by 20-30%.

Charger level selection

The charger level determines how quickly you replenish what you use — it doesn't change daily energy consumption, only charging speed. A Level 1 charger (120V wall outlet) adds about 4-5 miles per hour of charging — fine for short daily commuters but too slow for long-range drivers. Level 2 (240V) adds 20-30 miles per hour and fully charges most EVs overnight.

Existing solar field

If you already have solar, enter your system size to see if it covers the EV load. Many homeowners add solar when getting an EV because the math is compelling: the EV adds $50-100/month in electricity but solar can cover that for free after the investment payback.

The Formula

Daily kWh for EV = Daily Miles ÷ Efficiency (mi/kWh) Monthly kWh = Daily kWh × 30 Monthly Cost = Monthly kWh × Electricity Rate Cost per mile = Electricity Rate ÷ Efficiency Daily charge time = Daily kWh ÷ Charger kW Full charge time = Battery kWh ÷ Charger kW Solar panels to offset EV = Daily kWh ÷ (Peak Sun Hours × 0.86) ÷ 0.4 kW per panel

Electric vehicles are extraordinarily efficient energy converters — about 90% of electrical energy reaches the wheels, versus 25-35% for gasoline engines. This is why the per-mile electricity cost is $0.03-0.06 while gas vehicles cost $0.10-0.18 per mile — a 3-4x fuel cost advantage that solar can push even lower.

Example

Tesla Model Y LR — San Diego, CA

Emma drives 40 miles daily in her Model Y Long Range (100 kWh battery, 3.8 mi/kWh). She has a Level 2 32A charger and pays $0.28/kWh (California rate). She wants to know how many solar panels would cover EV charging.

Daily kWh to charge10.5 kWh/day

Monthly EV electricity315 kWh/month

Monthly charging cost$88.20/month

Cost per mile$0.074/mile

vs. 30 mpg at $4.50/galSave $60/month

Solar to offset EV

Additional solar needed2.7 kW (7 × 400W panels)

Solar panel cost (~$3/W)~$8,100 gross / ~$5,670 after ITC

Monthly savings with solar$88/month

Payback period~5.4 years

In California's high-rate environment, solar panels specifically sized for EV charging are an excellent investment — 5.4 years payback with 20+ years of essentially free EV fuel. Emma also qualifies for California's SGIP battery rebate and can charge from solar during peak rate hours, avoiding California's expensive peak-time-of-use charges.

FAQ

How much does it cost to charge an EV at home? ▼

At the US average rate of $0.15/kWh: $0.04/mile for an efficient EV (4 mi/kWh). Monthly cost for 40 miles/day: about $45-60. At California rates ($0.28/kWh): $0.07/mile, or $85-100/month for 40 miles/day. Compare to a 30 mpg car at $3.50/gallon: $0.117/mile or $140/month. EVs are 2-3x cheaper per mile even without solar.

How many solar panels do I need to charge an EV? ▼

A typical EV driving 40 miles/day uses about 10-12 kWh/day. At 4.5 peak sun hours with 86% efficiency, you need about 2.5-3 kW of solar — roughly 6-8 × 400W panels. In sunny climates (Phoenix, Miami), fewer panels are needed. In cloudy areas (Seattle, Portland), you may need 8-10 panels. A $7,500-9,000 solar addition specifically for EV charging typically pays back in 5-8 years.

What is the difference between Level 1 and Level 2 EV charging? ▼

Level 1 (120V, 1.4 kW): adds 4-5 miles per hour. Free to install (use existing outlet). Only practical for short daily commuters (under 40 miles). Level 2 (240V, 3.8-11.5 kW): adds 15-35 miles per hour. Requires NEMA 14-50 outlet or hardwired EVSE ($500-1,500 installed). Can fully charge most EVs overnight. Level 2 is the standard recommendation for most households.

Should I get a time-of-use rate for EV charging? ▼

Potentially yes. Many utilities offer time-of-use (TOU) rates with lower off-peak rates (often midnight-6am) as low as $0.05-0.08/kWh. If you charge overnight on a TOU rate, you can cut EV charging costs by 50-70%. With solar, the equation changes — daytime solar generation offsets peak-rate usage. Evaluate your utility's specific TOU plans; in some areas (California's NEM 3.0), TOU rates with solar and battery storage are the optimal setup.

Can my solar system charge my EV directly? ▼

Yes — if you have a grid-tied solar system, your EV charger can be powered by solar during the day (when production exceeds home consumption). Some smart chargers (Wallbox, ChargePoint Home Flex) optimize to maximize solar self-consumption. Without battery storage, surplus solar that doesn't charge the EV goes to the grid (at net metering rates). With battery storage, you can store solar to charge the EV at night — maximizing solar self-consumption and avoiding TOU peak rates.