What battery size do I need?

For most UK drivers doing 20-30 miles per day, a 40 kWh battery is more than sufficient. For 50+ miles per day or frequent longer trips without charging access, a 60-80 kWh battery provides more flexibility. Always factor in a 20% buffer for degradation and cold weather.

Should I get the biggest battery available?

Not necessarily. Bigger batteries cost more, weigh more (reducing efficiency), and take longer to charge. If 90% of your driving is under 50 miles per day, a smaller battery charged nightly at home is more cost-effective than paying thousands extra for range you rarely need.

What is the buffer for?

The buffer accounts for battery degradation over time, reduced range in cold weather, and the recommendation not to regularly charge to 100% or discharge below 10%. A 20% buffer is typical — meaning you should only plan to use 80% of the battery capacity for daily driving.

What if I occasionally need more range?

For occasional longer trips, you can charge to 100% and use the full battery, or plan charging stops using the rapid charging network. Most EV drivers find that 95% of their journeys are well within the daily range, and longer trips just need a 20-30 minute charging stop.

What battery size do I need for my daily commute?

For a 30-mile daily commute, a 40 kWh battery is plenty, giving 100+ miles of real-world range. For 60-mile daily driving, aim for 60+ kWh. Always buy more range than your minimum need to account for winter range loss and battery degradation over time.

CarCalcs

Battery Size Calculator

Calculate what battery size you need for your daily driving needs.

Weekday Daily Miles

Distance in miles

EV Efficiency

Ev efficiency in mi/kWh

Include weekend driving

Weekend Total Miles

Total miles across Saturday and Sunday

Battery Buffer

Reserve for degradation, cold weather, and not charging to 100%

How We Calculate This

This calculator determines the minimum battery size based on your longest daily driving need and desired buffer.

The Formulas

Daily energy need = Daily miles / Efficiency (mi/kWh)
Minimum battery = Longest day energy / (1 - Buffer %)
Recommended battery = Minimum rounded up to nearest 5 kWh

Frequently Asked Questions

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Last updated: February 2026

All calculations are estimates. Actual figures may vary based on driving conditions, vehicle specifications, and other factors.