How to Use This Tool
Reconcile electricity drawn at the wall with energy reported as added to the battery. Calculate EV home charging loss, efficiency, lost energy and electricity cost from wall and battery readings for one charging period.
The decision this tool supports
Dashboard battery energy and utility-meter energy use different boundaries, so comparing them without the wall-to-battery gap hides charging overhead. This page keeps the decision bounded to charging loss and the supporting outputs shown beside it. EV Charging Loss does not import an account, infer a market rate, or silently substitute an industry average.
Inputs and units
The EV Charging Loss calculation uses Energy drawn from wall, Energy added to battery, Electricity price. Keep all money values in one currency and all time, distance, mass, energy or volume entries in the unit printed beside the field. Mixing EV Charging Loss scopes can produce a plausible number with the wrong meaning.
- Energy drawn from wall is entered in kWh.
- Energy added to battery is entered in kWh.
- Electricity price is entered in currency/kWh.
Formula and worked check
Charging loss percentage = (wall kWh − battery-added kWh) ÷ wall kWh × 100; efficiency is the complementary stored share. A session drawing 40 kWh and adding 34 kWh is 85.0% efficient with 6.00 kWh, or $1.08 at $0.18/kWh, not stored. The EV Charging Loss default is an executable known-answer case, not a benchmark or recommendation. Change one input and verify that the direction of charging loss still matches the stated relationship.
How to interpret the result
Compare similar temperatures, starting state of charge and charging power; one session can be distorted by battery conditioning or measurement timing. The additional EV Charging Loss outputs expose the denominator, comparison, capacity or reverse value needed to audit the primary result instead of presenting one unexplained number.
Assumptions
- Wall and battery energy cover the same session boundary.
- Battery-added energy does not exceed wall energy.
- Electricity price is user supplied.
Save the EV Charging Loss input values and date with any material decision. A later EV Charging Loss rerun is reproducible only when the same assumptions and units are available.
Limitations and safety boundary
Vehicle estimates may not be calibrated energy meters; cabin conditioning, standby, charger overhead, temperature and rounding can enter the gap. EV Charging Loss is an estimate and cannot replace a contract, local code, licensed professional, calibrated measurement, lender statement or platform report where one governs the decision.
Source and privacy
The EV Charging Loss definition or rule was checked against U.S. EPA — Fuel Economy and EV Range Testing on 2026-08-26. Recheck U.S. EPA — Fuel Economy and EV Range Testing when a specification or policy behind EV Charging Loss can change. EV Charging Loss arithmetic runs in this browser tab; ecech does not receive the values through a calculation API.
Sources & assumptions
Tool Spec v2 · verified 2026-08-26. Platform rules and fees can change; the editable inputs remain authoritative for your account.
Official references
- U.S. EPA — Fuel Economy and EV Range Testing (checked 2026-08-26)
Model assumptions
- Wall and battery energy cover the same session boundary.
- Battery-added energy does not exceed wall energy.
- Electricity price is user supplied.
- Vehicle estimates may not be calibrated energy meters; cabin conditioning, standby, charger overhead, temperature and rounding can enter the gap.
