How to compare electric car charging tariffs
Start with your annual distance, battery-side consumption and the share of energy you can actually charge at home. Enter the home and public rates from your own bills. A low home tariff is useful only for energy you can buy during its applicable hours. Use a blended rate if you also charge outside that window.
All prices must use the selected currency. For a UK tariff of 25p/kWh, enter 0.25 with GBP selected. Enter tax-inclusive prices consistently. The currency selector does not convert prices.
Worked example: monthly home vs public charging cost
These are invented arithmetic inputs, not advertised rates: 12,000 km a year, 18 kWh/100 km, 10% losses at both billing boundaries, £0.25/kWh at home and £0.60/kWh publicly. The car needs 2,160 kWh in its battery and 2,400 billed kWh. At an 80% home share:
| Scenario | Average month | Year |
|---|---|---|
| 100% home | £50 | £600 |
| 100% public PAYG | £120 | £1,440 |
| 80% home / 20% public PAYG | £64 | £768 |
| Same mix, £8/month membership at £0.45/kWh | £66 | £792 |
Here, membership costs £24 more per year despite its lower unit price. A £0.15/kWh discount must cover the £8 monthly fee: £8 ÷ £0.15 = 53.3 eligible billed kWh per month. The example uses only 40 public kWh a month. At £1,000 net installation cost, home charging’s simple payback against all-public PAYG is £1,000 ÷ (£1,440 − £768), approximately 1.5 years. This excludes finance and maintenance.
Formulas and billing boundaries
- Battery energy = annual kilometres × kWh/100 km ÷ 100.
- Billed energy for each location = its battery energy share ÷ (1 − loss percentage ÷ 100).
- Annual mixed PAYG cost = home billed kWh × home price + public billed kWh × public price + additional home fixed costs.
- Subscription cost = mixed PAYG cost + 12 monthly fees − eligible public kWh × (PAYG price − member price).
- Subscription break-even billed kWh/month = monthly fee ÷ per-kWh discount, when the discount is positive.
If a consumption figure already measures electricity from the meter, set losses to zero on that same boundary. Public charging may meter energy at a different point from your home supply. Do not add upstream station losses that the quoted per-kWh bill does not charge to you. The defaults are assumptions, not measured average charging losses.
Is an EV charging subscription worth it?
It depends on eligible energy, the discount and the fee. Reduce the eligible share when you use other networks. The calculator assumes the subscription stays active for all twelve months; a holiday-only subscription needs a separate monthly comparison. Minimum terms, roaming rates, blocked chargers and session fees can change the outcome.
What if I cannot charge at home?
Set the home energy share to zero. The comparison then tests public PAYG against public membership; it does not count a home installation as usable. A zero home share or no recurring home saving produces no positive installation payback. An installed charger with a positive saving still needs a practical access and contract check.
Does a cheaper overnight tariff make the whole bill cheaper?
Not necessarily. Enter the effective rate for your charging hours, then check daytime household prices and standing charges outside this calculator. Only an extra fixed charge caused by your charging setup belongs in the additional home-cost field. Comparing the complete household bill is a different task.
Sources and scope
US Department of Energy: home charging and electricity cost factors. The comparison formulas and scenarios above are EVVerity’s original arithmetic. Prices and access must be checked with your supplier. Methodology and limitations.