Electric Car Charging Costs: Home vs Public Charging

How EV charging costs work

EV charging costs are not based on “a full tank”. They are based on energy, measured in kilowatt-hours (kWh).

A simple way to think about cost is:

• Charging cost (£) = energy added (kWh) × unit rate (price per kWh)

If you add 40 kWh and you pay 30p/kWh, your cost is:

• 40 × £0.30 = £12.00

Two practical points matter in real life:

• You rarely charge from 0% to 100%. Many drivers top up little and often.
• Not all energy drawn from the wall reaches the battery. Some is lost as heat (especially in cold weather). This is known as charging losses.

The difference between “battery size” and “energy used”

Your EV might have a 60 kWh battery, but you will not always use 60 kWh between charges. Your energy used depends on:

• How far you drive
• Your efficiency (miles per kWh)
• Your driving speed, weather, and use of heating

A small, efficient EV can use less energy than a larger SUV even if they drive the same distance.

Key factors that affect charging cost

Electricity tariff (your price per kWh)

At home, your unit rate depends on your electricity tariff. Many people are on a standard variable or fixed tariff. EV-specific tariffs often offer a cheaper overnight rate.

Important: if your tariff has a cheap overnight window but a more expensive daytime rate, it can be excellent for EV charging but less suitable if most of your household usage is during peak hours.

Charging location (home vs public)

Where you charge can change your unit rate dramatically.

• Home charging is usually cheapest (especially off-peak).
• Public charging tends to be more expensive because you pay for networks, maintenance, site costs, and convenience.

Battery size (kWh)

A larger battery can cost more to fill because it holds more energy.

However, battery size alone does not decide running cost. A larger, more efficient EV might still be cheap per mile if it travels many miles per kWh.

Driving efficiency (miles per kWh)

Efficiency is the biggest factor behind “cost per mile”.

• Higher miles per kWh = more miles for the same electricity = lower cost per mile
• Lower miles per kWh = fewer miles for the same electricity = higher cost per mile

Efficiency changes with:

• Motorway speeds
• Cold weather and cabin heating
• Tyre pressure and tyre type
• Carrying passengers and luggage
• Wet roads and headwinds

Home charging explained

Home charging is the baseline for EV running cost because it is where most drivers do most of their charging.

Standard domestic tariffs

If you charge on a normal domestic tariff, your cost is your unit rate per kWh multiplied by how much energy you add.

This is simple and predictable, but not always the cheapest option if you can shift charging overnight.

EV-specific off-peak tariffs

EV tariffs are designed to encourage you to charge when the grid is quieter, usually overnight.

Common features include:

• A cheaper unit rate for a fixed overnight window (for example 4–7 hours)
• A higher unit rate during peak hours (often late afternoon and early evening)
• A requirement for a smart meter

Before switching, check:

• Off-peak hours and whether they match your routine
• Peak unit rate (it can increase your household bill if you use a lot of electricity at peak times)
• Standing charge and exit fees
• Any charger or smart charging requirements

Smart chargers and scheduling

A smart charger lets you schedule charging so your EV uses the cheapest hours.

Scheduling matters because even with the right tariff, you only get the benefit if your car is actually charging during off-peak times. A smart charger can:

• Start and stop charging automatically
• Limit maximum charge (useful for battery health)
• Track energy use for EV charging separately
• Integrate with solar or home batteries (if you have them)

You can also schedule charging from the car itself in many EVs, but a smart charger is often more reliable and gives better reporting.

Typical home charging costs per full charge

To estimate home cost for a “full charge”, start with your battery size, then apply a realistic charging amount.

Many drivers use 10%–80% for day-to-day charging. That is 70% of the battery.

Example battery sizes:

• 40 kWh
• 60 kWh
• 80 kWh

Example “everyday” charge from 10% to 80%:

• 40 kWh battery → 28 kWh added
• 60 kWh battery → 42 kWh added
• 80 kWh battery → 56 kWh added

If you do occasionally charge to 100% at home, the simple estimate is battery size × unit rate, plus a small allowance for charging losses.

Cost per mile for EVs at home

Cost per mile is a quick way to compare EV charging with petrol and diesel.

You can estimate:

• Cost per mile (p) = unit rate (p/kWh) ÷ efficiency (miles per kWh)

Example (home at 28p/kWh):

• Efficient EV (4.5 mi/kWh): 28 ÷ 4.5 ≈ 6.2p per mile
• Average EV (4.0 mi/kWh): 28 ÷ 4.0 = 7.0p per mile
• Large EV (3.0 mi/kWh): 28 ÷ 3.0 ≈ 9.3p per mile

If you charge off-peak at a much lower unit rate, your pence-per-mile can drop sharply.

Public charging explained

Public charging can be convenient, essential for drivers without home charging, and critical for longer trips. It also tends to cost more per kWh.

Slow and fast chargers

Slow and fast public chargers are often used in:

• Car parks and supermarkets
• Streetside bays
• Leisure centres
• Hotels

They are typically used when you can leave the car for longer.

Key points:

• Pricing is usually per kWh, but some networks also have session fees or overstay fees.
• Some locations offer reduced rates for members.
• If a charger is free, there may still be parking fees or time limits.

Rapid and ultra-rapid chargers

Rapid and ultra-rapid chargers are common on:

• Motorway services
• Major routes
• High-throughput hubs

They are designed for quick top-ups. These are usually the most expensive kWh rates, but they save time.

Practical considerations:

• Charging speed depends on your car and battery temperature, not only the charger.
• Charging from 10% to 80% is typically faster than 80% to 100%.
• Some networks have cheaper off-peak pricing or subscriptions.

Typical public charging prices and cost per mile

Public charging prices vary by:

• Charger speed (slow/fast vs rapid/ultra-rapid)
• Network pricing
• Location (city centre vs motorway services)
• Memberships and time-of-day pricing

As a rule of thumb:

• Slow/fast public charging is often priced as a “mid-range” option.
• Rapid/ultra-rapid is priced as a premium convenience option.

If you want a quick estimate, use the same cost-per-mile calculation:

• Cost per mile (p) = unit rate (p/kWh) ÷ efficiency (miles per kWh)

The next section gives worked examples and a clear home vs public comparison.

Home vs public charging cost comparison

This section uses realistic example numbers so you can estimate your own costs.

Step 1: choose a realistic efficiency

Use your car’s trip data if you have it. If not, pick a sensible estimate:

Efficiency band	Typical driving profile	Efficiency (mi/kWh)
Excellent	Small EV, mixed roads, gentle driving	5.0
Good	Modern hatchback, mostly mixed driving	4.5
Average	Mixed driving, some motorway	4.0
Heavy / motorway	Large EV or frequent motorway driving	3.5
Winter worst-case	Cold weather + short trips	3.0

Step 2: estimate pence per mile at home

Example home rates:

• Standard home unit rate: 27.7p/kWh
• EV off-peak rate: 7–9p/kWh

Now the cost per mile:

Electricity price	4.5 mi/kWh	4.0 mi/kWh	3.5 mi/kWh
27.7p/kWh	6.2p	6.9p	7.9p
9p/kWh	2.0p	2.3p	2.6p
7p/kWh	1.6p	1.8p	2.0p

Even small changes in efficiency can be worth paying attention to if you drive a lot.

Step 3: estimate pence per mile on public charging

Example public rates:

• Slow/fast public charging: 54p/kWh
• Rapid/ultra-rapid charging: 76p/kWh

Public price	4.5 mi/kWh	4.0 mi/kWh	3.5 mi/kWh
54p/kWh	12.0p	13.5p	15.4p
76p/kWh	16.9p	19.0p	21.7p

Public charging can still be cost-effective compared with petrol or diesel in some cases, but it depends on your efficiency and how often you need rapid charging.

Typical costs per charge: quick reference

Use these examples as a sanity check. They assume you add the stated energy at the stated price.

10% to 80% top-up on a 60 kWh EV (about 42 kWh)

Where you charge	Example price	Cost for 42 kWh
Home (standard)	27.7p/kWh	£11.63
Home (EV off-peak)	7p/kWh	£2.94
Public slow/fast	54p/kWh	£22.68
Public rapid/ultra-rapid	76p/kWh	£31.92

Full charge on a 60 kWh EV (about 60 kWh)

Where you charge	Example price	Cost for 60 kWh
Home (standard)	27.7p/kWh	£16.62
Home (EV off-peak)	7p/kWh	£4.20
Public slow/fast	54p/kWh	£32.40
Public rapid/ultra-rapid	76p/kWh	£45.60

If you want a closer estimate, add 5–12% for charging losses depending on weather and charging speed.

Workplace and free charging options

Workplace charging can reduce your cost significantly if it is subsidised or free.

Common patterns:

• Free charging as an employee benefit
• Reduced rates compared with public networks
• Limited bays and time limits (move the car when done)

If you rely on free charging, plan for what you will do when it is unavailable. Having a backup public charging option near home or work reduces stress.

How to reduce EV charging costs

Use an EV tariff if your routine fits

If you can reliably charge overnight, an EV tariff is often the biggest cost lever.

• Set the car or charger to start within the off-peak window.
• Avoid peak charging unless you have to.

Charge to what you need, not to 100%

Charging to 100% is not necessary day-to-day for most drivers. For many EVs:

• 10%–80% covers most routines
• Save 100% charges for long journeys (when recommended by the manufacturer)

Reduce rapid charging when you can

Rapid charging is useful, but it is often the most expensive energy.

• Use rapid charging for trips, not weekly routine
• Plan stops around cheaper networks or off-peak windows where available

Improve efficiency

Small habits can reduce energy use:

• Keep tyres correctly inflated
• Drive smoothly and avoid high motorway speeds where practical
• Preheat the cabin while plugged in (in winter)
• Remove unnecessary weight

Track your real-world cost

Use your charger app, vehicle app, or a simple spreadsheet:

• kWh added per month
• total £ spent
• miles driven

This gives you your actual pence per mile, which is more useful than any generic estimate.

Is an EV cheaper than petrol or diesel?

It depends on how you charge and how you drive.

As a simple comparison:

• Home charging (especially off-peak) is often significantly cheaper per mile than petrol or diesel.
• Public rapid charging can narrow the gap and, in some cases, can approach petrol-like costs if your efficiency is low.

A petrol or diesel car’s “cost per mile” depends on:

• Fuel price per litre
• Real-world mpg
• Your mix of town vs motorway driving

If you are deciding between cars, the most accurate approach is:

1. Estimate your miles per year.
2. Estimate your EV efficiency (mi/kWh).
3. Estimate how much of your charging will be home vs public.
4. Compare pence per mile using the tables in this guide.

Before you commit: a quick checklist

• I know my typical efficiency (mi/kWh) for my driving.
• I know my home unit rate and whether an EV tariff would reduce it.
• I have a reliable way to schedule charging in off-peak hours.
• I know my nearest public chargers and their typical prices.
• I have a plan for longer trips (rapid charging stops and expected cost).
• I have compared EV pence per mile with my current petrol or diesel cost per mile.