How accurate is an EV charging time calculator?

Good enough to plan with, not to bet your last 5% on. Charging time depends on cell temperature, how busy the charging site is and the state of health of the pack. Wattrix models the taper curve rather than dividing kWh by kW, which puts it far closer than a linear estimate, but you should always keep the reserve you set.

Does Wattrix work offline?

Yes. A service worker caches the pages and scripts on your first visit, so Wattrix opens and calculates with no connection. That matters because underground car parks and rural charging stops are exactly where you need it.

Know what the drive really costs.

Q: Do I need an account to use Wattrix?

No. Wattrix has no accounts and no server-side component at all. The page you load is the whole product, and every calculation runs in your own browser.

Q: Which electric cars does Wattrix support?

Every one. There are 48 built-in presets for common models to save typing, but any EV works if you know the usable battery size in kWh and roughly what it consumes per kilometre.

Wattrix turns your car, your route and today's weather into four numbers you can act on: energy, time, stops and cost. Everything is worked out in your browser, so nothing about your journeys leaves your device.

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No sign-up, ever Works with no signal 48 models built in

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Battery (kWh)

Wh per km

Distance (km)

Price / kWh

Outside temperature 15°C

Energy

Reach

Cost

Adjust anything. The full tool adds charging stops, taper curves and comparisons.

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Presets for the cars people actually drive

Tools

Car presets

Accounts needed

100%

On your device

One profile, four answers

Everything an EV driver keeps guessing at

Set your car up once. Wattrix reuses it across every tool, so switching from planning a trip to checking a charging bill takes one click.

Trip planner

Distance in, answer out: do you make it on one charge, how many stops if not, how long each one takes and what the whole journey costs door to door.

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Charging session

How long from 20% to 80% on this particular charger, with the taper modelled properly. Shows why the last 20% is never worth waiting for.

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Range today

Your charge, today's temperature, today's roads. Real remaining range instead of the number on the dashboard.

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EV vs fuel

Running costs per 100 km and per year, against petrol, diesel or a hybrid, using your prices and your mileage.

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What people use it for

Built for the decisions, not the spec sheet

Every one of these is a question a real driver asks before they turn the key. Each card opens the calculator already filled in.

The long weekend drive

Helsinki to Lapland, London to Cornwall, Munich to the coast. Find out before you leave how many stops it takes and what the charging bill looks like.

Trip
Stops
Cost

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Winter range reality check

At -15 °C with winter tyres and the heater on, a 400 km car is not a 400 km car. See the real number before you commit to the drive.

Range
Cold
Safety

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Night tariff vs the motorway

Charging at home on a cheap overnight rate against paying rapid-charger prices. The gap over a year is usually the price of a holiday.

Cost
Tariff

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Should I switch from petrol?

Put your actual mileage, your actual electricity price and your current car side by side. No sales pitch, just the two numbers.

Compare
Fuel
Yearly

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Towing and roof boxes

A caravan can add 60% to consumption and a roof box 16%. Plan the trip with the load you are actually carrying, not the empty car.

Load
Towing

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Mileage claims and fleets

Work out the energy cost of a business trip to the cent, export it as CSV, and file it. Repeat trips can be saved and reloaded.

CSV
Expenses

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All use cases

How it works

Three inputs, then it gets out of your way

Pick your car

Choose from 48 presets or type your own battery size and consumption. Wattrix remembers it on this device for next time.

Describe the situation

Distance, starting charge, charger power, price, temperature, how you drive and what you are carrying.

Read the answer

Results update as you type. Share the link, export a CSV, print it, or save the scenario for trips you repeat.

Nothing to upload

There is no backend. Your car, your routes and your prices stay in this browser's local storage. Clearing your browser data deletes everything Wattrix knows.

The taper is modelled

Charging power drops as the battery fills. Wattrix integrates a real taper curve instead of dividing kWh by kW, which is why its 10 to 80% times look like the ones you see on the charger.

Weather counts

Cold batteries hold less and heat the cabin from the same pack. Temperature, speed, tyres and load all feed into the consumption figure the plan is built on.

Quick answers

Common questions

Do I need an account?

No, and there is nowhere to make one. Wattrix has no server-side component at all - the page you load is the whole product.

How accurate are the numbers?

Good enough to plan with, not good enough to bet your last 5% on. Consumption depends on wind, traffic, elevation and driving style, and charging depends on cell temperature and how busy the site is. Always keep the reserve you set.

Does it work without signal?

Yes. After your first visit the page is cached, so it opens and calculates with no connection - which is exactly when you tend to need it.

Which cars does it support?

Every one. There are 48 presets for common models to save typing, but any EV works if you know the usable battery size and roughly what it consumes.

Read the full FAQ and privacy notes

Stop guessing at the charger.

It takes about thirty seconds to set your car up, and it remembers it after that.

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