See every fee before you charge.
For residents using a charger selected by their building. Enter energy and session fees, model time and idle rules, then see one total you can compare.
Not a charging scheduler. ChargeWindow does not choose charging times or control your car or charger.
Session estimate
Building charger · 35 kWh
Whole session
£21.70
Added fees
£3.50
Rate shown
52p/kWh
Effective rate
62p/kWh
Worked session
35 kWh × 52p = £18.20 energy + £1.50 session + £2 time and idle = £21.70 total · 62p/kWh effective
Product definition
Reviewed
By Wolven Tech
What is ChargeWindow?
ChargeWindow is a £29, one-time EV charging cost calculator for residents using a charger selected by their building or parking operator. It does not find chargers, show live prices, schedule charging, or control a vehicle. You enter tariff values from the provider notice: energy rate, fixed session fee, charging-time rules, and idle fees. ChargeWindow adds those inputs deterministically to show the whole-session total, effective price per kWh, and driving cost per 100 miles or kilometres. This makes tariffs with different fee structures easier to compare before charging. Calculations and one saved tariff remain in your browser, no account is required, and the provider remains authoritative for current prices, availability, and terms. ChargeWindow is owned and created by Wolven Tech. It is designed for manual comparison, not financial advice, live tariff verification, route planning, solar optimisation, or a promise that one charging provider will be cheaper than another.
Read verified product facts →One calculation, useful answers
Read the bill your tariff implies.
ChargeWindow separates the advertised energy price from everything added around it.
Energy price in blue. Added fees in coral.
See session total, effective rate, cost per 100 miles, and the markup caused by non-energy fees.
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Private by design
Calculator runs in browser. No login, charger connection, or stored session history.
Read privacy policy →Compare like with like
One unit for every provider
Convert different fee structures into whole session cost and an effective rate per kWh.
Compare providers →Provider terms stay authoritative
No live-price guesswork
You copy current rates and rules from provider app, charger, or building notice. ChargeWindow handles the arithmetic.
Check product limits →Three steps
From tariff to total.
Fee guides
Know what each charge means.
What an EV charging session actually costs
Read energy, time, session, and other fees as one bill—not four unrelated numbers.
Read guideIdle fees: find the trigger before you plug in
Separate charging time from occupancy time and forecast the fee provider can add after charging changes state.
Read guideCompare charging providers without trusting headline rate
Normalize different tariffs against same charging session and same payment route.
Read guideEV charging cost calculator for flats and apartments
Add energy, session, connected-time and idle charges for one building-charger session. Worked UK flat example: £20.32 total and 72.6p/kWh effective.
Read guideDirect answers
Common questions.
What does an EV charging session cost?
Energy added multiplied by energy rate, plus any fixed session, time, and idle fees. ChargeWindow adds those amounts before calculating effective price per kWh.
Why can the effective price per kWh be higher?
A charger may lead with its energy rate. Effective price per kWh divides the complete session bill—including fixed and time-based fees—by energy delivered.
Does ChargeWindow use live charger prices?
No. You enter the tariff shown by your provider, charger, or building notice. That source remains authoritative for current prices and rules.
Does ChargeWindow choose or automate charging times?
No. ChargeWindow does not recommend a charging window, schedule a session, or control a car or charger. It calculates the cost of a session from tariff values you enter.
Where does my tariff data go?
The browser calculator runs locally. It requires no account and does not store your sessions on ChargeWindow servers.
Check the whole cost before the cable clicks in.
Pay once for browser access. Save one tariff locally, then add session usage whenever you need another calculation.