Solar Panel Size for EV Calculator
Size the home solar array needed to cover daily EV miles, with panel count and roof area.
- Daily EV Energy
- 11.4
- kWh/day
- Array Needed
- 3,048
- W
- 400W Panels
- 8.0
- count
- Roof Area
- 168
- sq ft
Calculator
EV miles per day
Miles per kWh
Peak sun hours
Live statistics
11.4
kWh/day
3,048
W
8.0
count
168
sq ft
Driving plans — pick your profile
Plans adjust the projected fuel use so estimates match how you actually drive. Your measured MPG stays untouched.
Results
Daily EV Energy
11.4kWh/day
Charging need
3,048W
Solar watts required
8.0count
Panels rounded up
168sq ft
About 21 sq ft per panel
Exact arithmetic on your inputs. Verify measurements and current rates for decision-grade figures.
Visualizations
Array Needed sensitivity
EV solar array
Formula
How Solar Panel Size for EV Calculator is computed from its inputs, with every derived figure shown.
Alternative Form
Variables
| Symbol | Name | Unit | Description |
|---|---|---|---|
| M | Daily miles | mi | Driven distance |
| E | Efficiency | mi/kWh | Vehicle economy |
| H | Sun hours | hrs | Peak equivalent |
Explanation
Driving energy from efficiency, array from yield balance at 0.75 derate, roof from standard panel footprint.
Derivation
Driving energy from efficiency, array from yield balance at 0.75 derate, roof from standard panel footprint.
Step-by-Step Calculation
Follow each step to understand how the result is calculated from your inputs.
Set daily miles.
Set ev efficiency.
Set sun hours.
Convert miles to kWh, size watts, count panels and roof.
Worked Examples
See how the calculator works with different scenarios.
Scenario
40 mi at 3.5 mi/kWh, 5 sun.
Inputs
Calculation
Apply the stated formula to the example inputs; the primary result follows the steps above.
Result
Array Needed 3,048 W.
Interpretation
Near 3,048 W, 8 panels.
Understanding Your Result
Your Result: Daily EV Energy: 11.4 kWh/day
Typical range: Five sun hours with 0.75 derate is a solid planning baseline. Daily camper loads commonly 500 to 2000 Wh; EV miles need house-scale arrays.
What This Means
Daily EV energy is miles over efficiency. Array watts equal that energy over sun hours over derate; panels and roof follow.
Why It Matters
Car roofs harvest a few miles daily; real EV offset needs house-scale arrays. This sizes that array honestly.
Professional Interpretation
Installers audit loads with meters, size arrays to worst-season sun, and pair panels with batteries sized for nights plus storm days.
How the plan factor applies
Plans do not scale physics results here; selections are recorded while energy figures follow sun and load.
Loads first
Metered daily watt-hours precede every panel and battery decision.
Recommendations
- •Watt-hour budgets end dead-battery surprises
- •Sun-hour math sizes arrays honestly
- •Charge-time views plan around weather
- •Cost views price energy independence
Learn — fuel economy, deeply
Vehicle solar is an energy budget: panel watts times sun hours times system efficiency must cover the load. Calculators in this group size panels, time solar charging, budget EV, camper, RV and battery charging, and price solar energy against fuel and hookups.
1 · Where the gallon goes (energy path)
Engine heat
60–70% lost
Coolant + exhaust carry most energy away. Hybrids recover some via Atkinson cycle + regen.
Driveline
5–15% lost
Transmission, differential, accessories. CVTs and 8–10 speed autos lose less.
Aero drag
∝ v²
Doubles from 55→78 mph. Roof boxes hurt more than trunks.
Rolling + brakes
10–20%
Tires, weight, stops. Regen braking (hybrid/EV) reclaims city braking energy.
2 · What EPA / WLTP ratings actually mean
- City cycle — stop-and-go, 21 mph average, idle included. Hybrids shine here (regen + engine-off).
- Highway cycle — steady 48 mph average with gentle accelerations. Aero and gearing dominate.
- Combined — 55% city + 45% highway weighting. The single number most drivers should compare.
- Real-world gap — expect 5–15% below the sticker with normal driving; hypermilers can beat it, aggressive drivers miss by 25%+.
- MPGe — 33.7 kWh = 1 gallon-equivalent. A 120-MPGe EV uses ~⅓ the energy per mile of a 35-MPG car.
3 · Factor-impact table — what moves your number most
| Factor | Typical impact | Why |
|---|---|---|
| Speed above 55 mph | −5 to −25% | Aero drag rises with v². Each 5 mph over 55 ≈ +$0.30–0.50/gal equivalent. |
| Aggressive driving | −10 to −30% | Hard acceleration + braking wastes kinetic energy, especially in the city. |
| Under-inflated tires (−5 PSI) | −2 to −4% | Higher rolling resistance. Check monthly; pressure drops ~1 PSI per 10°F. |
| Roof rack / cargo box | −5 to −25% | Empty rails ≈ −5%; loaded box at highway speed up to −25%. |
| Excess weight (+100 lb) | −1 to −2% | Matters most in stop-and-go. Clean the trunk before long trips. |
| A/C at city speed | −5 to −15% | At highway speed A/C beats open windows (drag). Use recirculation. |
| Cold weather (20°F vs 77°F) | −10 to −20% | Rich warm-up mixture, thicker fluids, winter-blend fuel, heater load. |
| Clogged air filter / bad O2 sensor | −4 to −40% | A failed oxygen sensor alone can cut economy by up to 40%. |
| Idling | 0 mpg | 0.2–0.5 gal/hr burned standing still. Restart beats 30 s+ idling. |
| E10 → E85 fuel switch | −15 to −30% | Ethanol carries less energy per gallon; flex-fuel range drops accordingly. |
Winter playbook
- • Expect −10 to −20% on short trips; combine errands on one warm engine.
- • Tires lose ~1 PSI per 10°F — re-inflate monthly.
- • Idle 30 s max, then drive gently; cabin heat comes faster under light load.
- • Winter-blend fuel has slightly less energy — a 2–3% seasonal dip is normal.
Summer playbook
- • City: windows down under ~45 mph; highway: A/C + recirculation beats open windows.
- • Park in shade; ventilate before blasting A/C.
- • Hot asphalt softens tires — still check pressure, heat raises it.
- • Roof cargo hurts most in summer road-trip season — move it inside or to a hitch carrier.
4 · Measure like a pro (the 3-tank protocol)
- Fill to first click at the same pump, record the odometer (Tank 0).
- Drive normally for 2–3 tanks; always refill to first click at the same pump.
- MPG = total miles ÷ total gallons across all tanks — averaging kills pump-click noise.
- Cross-check with the trip computer; a persistent >10% gap means the computer needs calibration — or the car needs service.
- Log with an OBD-II dongle for per-trip MPG if you want to isolate commute vs. highway behavior.
Practical Tips
- •Measure loads with a meter, not labels
- •Face panels to the sun when stationary
- •Clean dust; output drops fast
- •Size wire and fuses with the panels
- •Track sun hours by season
- •Keep a generator or hookup backup
Common Mistakes
Assumptions
This calculator makes the following assumptions to provide estimates:
Limitations
Be aware of these limitations when using this calculator:
Frequently Asked Questions
Answers to common questions about this calculator.
How does the Solar Panel Size for EV Calculator work?
What is a peak sun hour in the Solar Panel Size for EV Calculator?
How much margin belongs in the Solar Panel Size for EV Calculator?
How accurate is the Solar Panel Size for EV Calculator?
Can the Solar Panel Size for EV Calculator replace a generator?
How many solar watts does my camper need?
How long does solar charging take?
Can solar charge an EV?
How do I size panels for an RV?
What does solar energy cost?
How much battery do I need?
Do panels work in winter?
What is peak sun hour?
Solar versus generator for RVs?
Related Calculators
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Related Guides
Deepen your understanding with these educational resources.
Glossary
Technical terms used in mortgage calculations explained in plain language.
- MPG
- Miles per gallon. Distance travelled per gallon of fuel; higher is better. US gallon = 3.785 L.
- L/100 km
- Litres consumed per 100 kilometres; lower is better. Standard metric efficiency unit.
- MPGe
- Miles per gallon-equivalent. EV metric: miles travelled on 33.7 kWh (energy of 1 gal of gasoline).
- CAFE
- Corporate Average Fuel Economy — US fleet-average efficiency standard enforced by NHTSA.
- Rolling resistance
- Energy lost deforming tires as they roll. Low-pressure or wide tires raise it.
- Aerodynamic drag
- Air resistance growing with the square of speed — why highway MPG falls fast above 60 mph.
- Hypermiling
- Driving techniques (coasting, steady speed, anticipation) that maximise real-world MPG.
- OBD-II
- On-board diagnostics port. Scanners and dongles read live MPG, fuel trim and fault codes.
- Peak sun hour
- One hour at 1000 W per square meter. Sizes daily energy.
- Derate
- Combined loss factor for heat, dirt, wiring and conversion.
- Autonomy
- Days of use covered without new solar input.
Authoritative References
Trusted sources and standards referenced by this calculator.
Applicable Standards
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Page Information
2026-09-24
2.0.0
Free to use for educational and professional purposes.
How you compare — vehicle class averages
| Class | Combined MPG | City / Hwy | Fuel / 12k mi | Cost @ $3.50 | CO₂ / yr |
|---|---|---|---|---|---|
| Compact sedan | 34 | 30/40 | 353 gal | $1,235 | 3.1 t |
| Midsize SUV | 25 | 22/29 | 480 gal | $1,680 | 4.3 t |
| Pickup truck | 19 | 17/23 | 632 gal | $2,211 | 5.6 t |
| Hybrid sedan | 49 | 50/47 | 245 gal | $857 | 2.2 t |
| EV (MPGe) | 115 | 125/105 | — (electric) | $550 | 1.1 t |
Combined averages blend EPA city/highway cycles. EV row shows MPGe and home-charging cost; tailpipe CO₂ is zero, grid CO₂ ≈ 1.1 t/yr.
Maintenance checklist
Tick off what you already do — your car scores 1/6 (17%).