How we calculate

1. Where does the data come from?

Vehicle data comes only from Tesla's official Fleet API and Fleet Telemetry, with the consent the vehicle owner gives on Tesla's own screen. No hardware, no Tesla password.

Access is read-only: we never send commands and never wake a vehicle. A sleeping vehicle therefore sends no data; the calculations account for this (see below).

• Charging sessions: start/end, energy added to the battery, peak charging power, AC/DC, location.
• Odometer and battery level (for distance, efficiency and battery health).
• Tesla Supercharger history: the amount Tesla billed — this is an actual cost.

2. How do we know where charging happened?

We never ask for addresses. Home and workplace are detected from location history:

• Home: each night the vehicle's last parking location between 18:00 and 03:00; in 150 m clusters, the place seen on at least 4 different nights and at least 40% of observed nights is home.
• Workplace: on weekdays, the place where the vehicle stays longest between 09:00 and 15:00; same thresholds and at least 400 m from home. Fast-charging sites never count as a workplace.
• Public charging: the station within 150 m of the charging location is looked up in the country's official charging-station register (Turkey: EPDK). The station's network (e.g. ZES, Eşarj, Trugo) is recognised from that register.
• Supercharger: from Tesla's charging history.
• You can dismiss an automatically detected place at any time; it is not suggested again.

3. Charging cost

When an actual amount exists (Supercharger invoice, uploaded invoice/receipt) it is always used and marked "actual". Otherwise the amount is estimated and shown as "estimated" together with its reasoning. When an actual amount arrives, the estimate is removed automatically.

An estimate has two steps: first the energy drawn from the grid, then the price.

• Grid energy: as measured by the charger when available; otherwise energy added to the battery ÷ (1 − charging loss). Assumed loss: company setting for AC (default 10%), 5% for DC.
• Home / workplace: energy is split across tariff bands in proportion to the session time in each band and multiplied by that band's price. Your own tariff is used if defined, otherwise the country's official default tariff (Turkey: EPDK residential and commercial three-rate; UK: Ofgem price cap). The explanation says when a default is used.
• Dynamic (hourly) tariffs: day-ahead market prices in 15/30-minute slots (Energy-Charts: DE-LU, NL, BE, AT, CH; UK: Octopus Agile), plus your tariff's multiplier and per-kWh adder.
• Public charging: the list price of the station's network (AC, DC and high-power DC separately), excluding VAT because companies can reclaim it. If the network is unknown, the median price of networks is used — never the home tariff, which would understate the cost. Membership and promotional discounts are not known and not applied.
• The price catalogue is dated: every estimate states the period and source of the price used.

4. Savings opportunities

Each item in the savings report is calculated separately, and overlaps are avoided before items are added together:

• Charging at expensive hours: the difference if home/workplace charging had been done in the cheapest band of the same tariff (achievable with scheduled charging in the vehicle).
• Fast-charging premium: the difference if public-station and Supercharger kWh had cost your own average home/workplace price per kWh that month.
• Tariff recommendation: home/workplace charging of the last 90 days is re-priced with the other tariff structures available in your country (e.g. single-rate / three-rate, an EV tariff in the UK). "Current charging times" and "with scheduled charging" are shown separately; no recommendation is made below a 5% difference. If we don't know your tariff, the country's standard tariff is assumed and this is stated. Other consumption on the meter is unknown, so only vehicle charging is compared.
• Diesel/petrol equivalent: what would a vehicle driving the same distance cost with the consumption (L/100 km) and fuel price you set? Only vehicles with odometer data at period start/end and charging energy consistent with distance are counted.

5. Before / after and the savings guarantee

The 30 days from the first charging record are your fleet's baseline (cost per kWh, cost per km, fast-charging share). At the end of day 30 the report is emailed to managers; every later period is compared with this baseline.

For the savings guarantee, value = opportunities found + realised savings (drop in cost per kWh versus the baseline × that month's kWh). The EV-versus-diesel saving is not included, because it is not our doing. If the value falls short of the monthly subscription fee, that month's fee is refunded. Conditions: paid subscription, month completed and the cost of at least 90% of charging sessions known (Terms of Service section 7.5).

6. Carbon report

We follow the GHG Protocol Corporate Standard. Scope 1 is zero because EVs burn no fuel; charging electricity is reported under Scope 2 using the location-based method: grid kWh × the country's grid emission factor (adjustable in settings).

Avoided emissions = direct emissions of a combustion vehicle driving the same distance − the EV's Scope 2 emissions. If recorded charging energy is below 10 kWh per 100 km (meaning some charging was not seen), that vehicle-month is excluded from avoided emissions. The report does not replace independent assurance.

7. Battery health

Only readings taken at 40% state of charge or higher are used, as daily medians; no value is shown with fewer than 5 days of readings. The reference is the new-vehicle value you enter or, after 60 days of history, the value of the first 30 days; health is capped at 100%.

A Battery Health Passport is a frozen copy of these values; anyone can verify it via its QR code and the issuer can revoke it. It is an estimate and does not replace a Tesla service diagnosis.

8. What we never do

• We don't invent figures: a value that cannot be calculated is shown as "—", not produced as a guess.
• We don't silently mix actual and estimated amounts; every line shows its type and source.
• We don't wake vehicles or send them commands.
• We don't sell your data; location history is deleted after the retention period you set.