Our methodology
Charging cost
Battery energy in kWh equals usable capacity multiplied by the percentage-point change in charge, divided by 100. Grid electricity divides battery energy by charging efficiency expressed as a fraction. Multiplying by the VAT-inclusive unit rate gives estimated charging cost.
The estimate excludes standing charges, installation and public charging. The prefilled values are illustrative inputs, not measured market averages. Changing country clears monetary inputs so a GBP rate cannot be silently reused as EUR; no exchange-rate conversion is applied.
Charging time
We take the minimum of the vehicle AC limit, charger power and optional property limit. For single-phase or unknown supply, we also apply an assumed 7.4 kW ceiling; this does not establish the actual single-phase capability of the car. Delivered power multiplies that minimum by efficiency. Dividing required battery energy by delivered power estimates hours.
An optional charging window estimates the charge reached up to the target and additional charging time required. This AC model assumes constant power and ratings valid for the actual supply phases. Cold batteries, tapering, scheduled pauses and load management can increase the time. Ties between limits are shown together.
Tariff comparison
Driving energy uses either miles per kWh or kWh per 100 km, with the exact conversion 1 mile = 1.609344 km. We multiply by home charging share and divide by charging efficiency for battery-based figures; meter-based figures already include those losses. Household electricity excludes EV consumption.
EV and household energy each use a separate off-peak share. We add daily standing charges for 365 days, then compare with the entered flat-rate scenario. A negative saving means the entered tariff costs more. We also solve the EV off-peak share needed to match the comparison bill, keeping household use fixed. Negative unit prices are supported, but this is not a forecast of dynamic prices.
Charger matching
We exclude chargers outside your country, incompatible supply phases, unknown or over-budget hardware prices and missing required supplier integrations. Smart capability and mandatory supplier integration are separate controls; a supplier preference alone does not exclude other products. Scores award 20 points for meeting the vehicle AC limit capped by the assumed supply limit, 25 for requested solar capability, 20 for hardware budget, 10 for cable preference, 15 for a listed supplier integration and 10 for load balancing.
Scores depend on your preferences and available evidence. Unknown prices are excluded; qualifying prices earn budget points. Installation costs are separate. Warranty and grant eligibility need contextual review and are not included in the score.
Corrections and limitations
Check source dates before acting. We aim to make assumptions inspectable and correct errors at the source. The same calculation functions power the tools and automated tests.