TECH TORQUE MEDIA INVESTIGATION
Independent real-world analysis based on several months of smart charging and electricity billing data.
The EV Bill Audit: How to Check Whether Your Smart Charging Tariff Is Really Working
By Tech Torque Media
Your EV Knows One Thing. Your Electricity Bill Knows Another.
One of the biggest advantages of owning an electric car is lower running costs.
Instead of filling up at a petrol station, you’re charging at home, often overnight on a discounted electricity tariff. If you’re comparing tariff options, MoneySavingExpert maintains a useful EV energy tariff guide. Every month your car records how much electricity it has received, your home charger logs every charging session and your electricity supplier records every unit of electricity consumed.
So surely all three should tell exactly the same story?
Not necessarily.
After independently reviewing several months of real-world smart charging data, Tech Torque Media developed a simple audit process to compare EV charging records with half-hourly electricity bills.
The aim wasn’t to catch an energy supplier making mistakes.
It was to understand how modern smart charging actually works—and how EV owners can confidently verify their own charging costs.
Why Your Numbers Don’t Match
One of the first things many new EV owners notice is that every system reports a different figure.
Your vehicle reports one number.
Your charger reports another.
Your electricity bill reports something different again.
That doesn’t automatically mean one of them is wrong.
| Source | What it Measures |
|---|---|
| Vehicle App | Energy successfully stored inside the battery |
| Home Charger | Electricity delivered during charging sessions |
| Electricity Bill | Total electricity supplied to your entire home |
Understanding this difference is the first step towards understanding your true running costs.
Charging Losses: The Missing Part of the Story
When electricity travels from your home’s consumer unit to your EV battery, a small percentage is inevitably lost.
Energy passes through:
- Your home wiring
- The charging cable
- The vehicle’s onboard charger
- The battery management system
Some of that energy becomes heat.
Most modern AC home charging systems operate at approximately 90–93% efficiency.
That means if your vehicle stores 90 kWh in its battery, your electricity meter may record around 97–100 kWh leaving the grid.
This is completely normal and explains why your electricity bill is always slightly higher than the figure shown inside your vehicle.
Your Electricity Bill Doesn’t Just Measure Your Car
Another common misconception is assuming your overnight electricity usage belongs entirely to the EV.
It doesn’t.
Your electricity meter records everything happening inside your home.
That could include:
- Refrigerators and freezers
- Broadband equipment
- Dishwashers
- Washing machines
- Heat pumps
- Hot tubs
- Home battery systems
- Everyday background electrical loads
Once household consumption and normal charging losses are considered together, the numbers usually make far more sense.
Is This Audit Relevant To Every EV Owner?
Not necessarily.
If you’re using a standard charger or a simple timer that charges your vehicle during fixed overnight off-peak hours, checking your electricity bill is usually straightforward. As long as your charging stays within your tariff’s cheap-rate window, there is generally very little to audit beyond confirming the correct tariff has been applied.
Smart charging tariffs are different.
If your vehicle or home charger is paired directly with a smart tariff—such as Intelligent Octopus Go—your electricity supplier can automatically start, pause and resume charging throughout the day or night to help balance demand on the electricity grid.
That means some charging sessions may take place outside the normal overnight off-peak window while still qualifying for the cheaper electricity rate.
Because charging schedules become dynamic rather than fixed, comparing your charger history with your half-hourly electricity bill becomes much more valuable.
It allows you to verify that your charging sessions appear to have been billed in accordance with your tariff.
How To Audit Your EV Electricity Bill
After reviewing several months of charging data, we developed a straightforward five-step process.
It typically takes less than ten minutes each month.
Step 1 – Download Your Electricity Bill
If your supplier provides detailed half-hourly electricity data, download the full statement.
Those 30-minute readings form the basis of the audit.
Step 2 – Open Your Charger App
Most smart chargers record:
- Charging start time
- Charging finish time
- Energy delivered
- Charging duration
These records become your reference point.
Step 3 – Identify Higher Electricity Usage
One useful indicator is unusually high electricity consumption.
In many households, sustained electricity usage above approximately 3 kWh during a single 30-minute period often indicates that the EV charger was active.
Readings above 4 kWh deserve an even closer look because the household is very unlikely to sustain this level of electricity consumption for a full 30-minute period without the EV charger contributing significantly.
This doesn’t prove your vehicle was charging.
It simply identifies the half-hour periods that deserve further investigation.
Step 4 – Compare The Timings
Now compare your charger’s charging history with your electricity bill.
Ask yourself:
- Was the charger active?
- Does the electricity usage reflect that charging session?
- Was the correct electricity tariff applied?
- If you’re using a smart charging tariff, does charging outside the normal overnight window appear to have been billed correctly?
Looking at all three data sources together provides a much clearer picture than relying on any single app.
Step 5 – Look For Patterns, Not Individual Readings
Perhaps the biggest lesson from our review was this:
Don’t jump to conclusions because of one unusual half-hour.
Modern smart charging systems constantly optimise charging schedules to help balance demand on the electricity grid.
An isolated reading may have a perfectly reasonable explanation.
Instead, review several months of charging history.
If similar discrepancies appear consistently, you’ll have much stronger evidence should you ever need to ask your energy supplier to investigate.
What We Learned
Reviewing several months of charging data highlighted just how sophisticated modern smart charging has become.
The overwhelming majority of charging sessions aligned exactly as expected.
Standard overnight charging matched the cheaper electricity tariff.
Smart charging sessions scheduled outside the traditional overnight period generally appeared to be billed correctly.
Occasionally, individual charging periods deserved a closer look because the charging records and billing data did not immediately appear to align.
That doesn’t automatically indicate a billing error.
It simply demonstrates the value of understanding your charging data and reviewing it periodically.
Key Takeaways
✓ Your EV app measures energy delivered to the battery.
✓ Your electricity bill measures energy drawn from the grid.
✓ Smart charging can occur outside the standard overnight off-peak window while still qualifying for the cheaper rate, depending on the tariff terms.
✓ Always compare your vehicle, charger and electricity bill together.
✓ Look for recurring patterns over several months before assuming there’s a billing issue.
Why Every EV Owner Should Understand Their Charging Data
Electric vehicles generate an enormous amount of useful information.
Your vehicle records charging history.
Your charger records every charging session.
Your electricity supplier records every half-hour of electricity consumed.
Together, those three systems provide an incredibly detailed picture of how your vehicle is being charged.
Most owners never look beyond the monthly Direct Debit leaving their bank account.
But spending ten minutes reviewing your charging history can provide reassurance that everything appears to be working as expected—and help you ask informed questions if something genuinely doesn’t look right.
The Tech Torque Media Verdict
Owning an electric vehicle today isn’t simply about plugging in and driving away.
It’s about understanding the technology quietly working in the background.
Across our EV charging and ownership coverage, modern smart charging systems are remarkably capable, but they also generate a wealth of information that can help owners better understand their true running costs.
By comparing your vehicle, your charger and your electricity bill, you can build a much clearer picture of how your EV is being charged and how your electricity tariff is being applied.
In our experience, most charging sessions match expectations remarkably well.
The purpose of an audit isn’t to catch your energy supplier out.
It’s to understand how your smart tariff works, verify that your charging history makes sense and recognise when something genuinely deserves a second look.
As electric vehicles become increasingly connected, understanding your charging data is becoming just as important as understanding your car.
Editorial Transparency
This article is based on Tech Torque Media’s independent review of several months of real-world smart EV charging data. Our testing compared vehicle charging records, smart charger session logs and half-hourly electricity billing to develop a repeatable audit process for EV owners. The purpose of this guide is to help readers understand their charging data rather than suggest that billing discrepancies are widespread. Charging behaviour, tariff rules and billing systems vary between suppliers and charger manufacturers, and readers should always refer to the terms and conditions of their own electricity tariff.
