Tariff Calculator: Standard vs Day/Night

Compares annual cost including EV charging, household peak/off-peak usage, and standing charges.

Inputs

Usage assumptions (applies to both tariffs) Average annual mileage — miles/year Miles per kWh of vehicle — miles/kWh

EV energy (kWh/year) = mileage ÷ (miles per kWh)

Average peak consumption (household) — kWh/year Average off-peak consumption (household) — kWh/year

These are your non-EV household kWh split between peak/off-peak.

% of EV charging done off-peak

80%

Used only for the day/night tariff. Standard tariff assumes a single unit rate.

Standard tariff inputs Unit rate — pence/kWh Standing charge — pence/day

Day/Night tariff inputs Peak (day) unit rate — pence/kWh Off-peak (night) unit rate — pence/kWh Standing charge — pence/day

EV energy used —

kWh/year

Total annual consumption (EV + household) —

kWh/year

Standing charges (annual) —

Standard vs Day/Night

Standard tariff total cost —

Unit rate + standing charge

Day/Night tariff total cost —

Peak/off-peak unit rates + standing charge

Recommendation —

Break-even EV off-peak % —

Minimum EV off-peak charging % needed for day/night to match standard (given your household split + standing charges).