# How to Read Your EV Charging Session Data By EV Charge Cables ยท Published 18 October 2026 **The short version** Your EV charging session data shows energy added in kWh, charge rate in kW, session duration, start and end state of charge, and cost, giving you a clear picture of every charge. - kWh added is your key energy figure; charge rate shows how fast it arrived - State of charge at start and end tells you how much of the battery you used - Download session history from your car's app or the network portal for expense records Your EV's charging session data tells you how much energy entered the battery, at what speed, over what period, and in many cases what it cost. Learning to read it takes a few minutes and gives you a much clearer picture of your real-world energy use, whether you charge at home with a [charging cable](https://www.evchargecable.co.uk/collections/ev-charging-cables) and wallbox or top up at a public rapid charger. Most of the information you need is in your car's dashboard display, the manufacturer's companion app, or the charging network's app. | Data field | What it means | Where to find it | | --- | --- | --- | | Energy added (kWh) | Total electricity delivered to the battery during the session | Car display, manufacturer app, charger receipt | | Charge rate / power (kW) | Speed at which electricity is currently flowing into the battery | Car display, wallbox or public charger screen | | Session duration | Total time plugged in and charging | Manufacturer app, charger receipt | | Start and end state of charge (%) | Battery level when you plugged in and when you unplugged | Car display, manufacturer app | | Cost | Charge for the session, based on kWh or time billing | Public charger receipt, network app, home energy bill | ### What is kWh and why does it matter? Kilowatt-hours (kWh) are the unit of energy used in EV charging, in the same way that litres measure petrol. When a session shows "10 kWh added", that is the energy that entered the battery. Your car's total battery capacity is also measured in kWh, so dividing energy added by total capacity gives a sense of how much of the battery you filled. Home charging is billed in pence per kWh on your electricity tariff; public charging may be billed per kWh, per minute, or as a flat session fee. Check your tariff and the network's app for current pricing. ### How do you read charge rate and what limits it? Charge rate, shown in kilowatts (kW), tells you how fast energy is flowing into the battery right now. This figure changes during a session: it may start lower if the battery is cold, rise as the battery warms, and taper off as the battery approaches full, particularly on rapid DC chargers. The rate shown is always the actual rate in use, limited by whichever of three things is smallest: the charger's output, the cable's current rating, or the car's onboard charging capacity. If the rate seems unexpectedly low, check whether the cable is rated for the charger's full output. ### What is state of charge and how should you use it? State of charge (SoC), shown as a percentage, tells you how full the battery is. A session starting at 20% and ending at 80% added 60 percentage points of capacity. The important nuance is that filling from 80% to 100% takes disproportionately longer than filling from 20% to 40% on a rapid DC charger, because the BMS tapers the charge rate to protect the cells. Reading start and end SoC alongside kWh added also helps you estimate usable battery capacity, which narrows gradually as a battery ages over many years. ### Where can you view your session history? Most EV manufacturers offer a companion app that stores a history of charging sessions: kWh, duration, start and end SoC, and sometimes estimated cost. Public charging networks such as BP Pulse, InstaVolt, Osprey, Pod Point, and Shell Recharge also store session history in their apps or online account portals, and most email a receipt after each session. Your home wallbox may have its own energy dashboard. Combining all three sources gives a complete picture of your charging habits and costs over time. ### How can session data help you save money? Reviewing a month of session data shows which sessions were most expensive and why. If most of your energy comes from a home tariff, confirming that sessions complete during the cheap overnight window tells you whether you are capturing the off-peak rate. A session showing a low kWh figure for a long duration may indicate the car was paused or the wallbox had a connectivity issue. Tracking kWh per session against driven miles gives you a real-world efficiency figure more accurate than the official WLTP test result. ### What does a public network receipt tell you? A receipt from a public charging network typically shows: site address and charger identifier, session start and end times, total energy in kWh, the billing rate, and total cost. Some networks also show the peak charge rate achieved. Keep receipts if you claim charging costs through an employer or business, as HMRC may require evidence. For current guidance on claiming business charging costs, refer to HMRC's published rules at gov.uk, which are updated periodically. ### Frequently asked questions #### Why does the kWh on a public charger differ from my car's display? Small losses occur in the charging cable and the car's onboard charger as alternating current is converted to direct current for the battery. The charger measures energy leaving its end; the car measures energy arriving at the battery. The difference is normal and typically modest, varying by car, charger, and cable condition. For billing, the charger's figure is what you are charged. #### Can I use charging session data to claim back VAT or tax? Potentially, for business users. HMRC sets rules on claiming business electricity costs for EV charging, and these change over time. You will need records of energy delivered and, for public charging, receipts showing kWh and cost. Speak to your accountant and check current HMRC guidance at gov.uk before making any claim; this guide does not constitute tax advice. #### How accurate is my car's range estimate after a charge? Range estimates are calculated using recent driving patterns, battery level, temperature, and other factors. They are an approximation, not a guarantee. The official WLTP figure in the car's specification does not reflect every driver's real-world conditions. Your session data matched to driven miles gives a more reliable picture of your specific car's real efficiency. #### My wallbox app shows a different energy figure from the car. Which is right? Both are measuring at different points in the charging chain. The wallbox measures energy leaving its socket; the car measures energy entering the battery. The difference is cable and conversion losses. For billing purposes, the wallbox figure is what you are charged for. For battery management purposes, the car's figure is more relevant. #### How do I know if I am on the best tariff for home charging? Your session data shows how many kWh you use at home per month. Multiply this by your current per-kWh rate to see your monthly EV charging cost, then compare that with off-peak EV tariffs your supplier or others offer. Many energy suppliers offer overnight cheap-rate windows specifically for EV charging; check your supplier's options and comparison sites for current rates. #### Can I export my session data? Many manufacturer apps and network portals allow you to download session history as a CSV or PDF, which is useful for expense reporting or tax records. Check the settings or account section of your car's app or the relevant network's online portal. Not all apps offer export; if yours does not, screenshot or manually log monthly totals. Your session data is a genuinely useful tool for managing charging costs and spotting equipment issues. If a session prompts you to check your cable, browse our [EV charging cables](https://www.evchargecable.co.uk/collections/ev-charging-cables) to make sure your setup is running at full capacity. For more practical charging advice, visit our [guides library](https://www.evchargecable.co.uk/blogs/guides). --- Canonical version: https://www.evchargecable.co.uk/blogs/guides/how-to-read-your-ev-charging-session-data EV Charge Cables, EV charging cables matched to your car: https://www.evchargecable.co.uk. Some links in this article are Amazon affiliate links; as an Amazon Associate we earn from qualifying purchases at no extra cost to you.