Deep-dive guide
EV Home Charging vs Public Station Simulator: Does a Wallbox Pay for Itself?
Executive industry analysis
Choosing between home charging and public stations looks like a simple question about price per kilowatt-hour. At home you pay your domestic tariff, often with a cheaper night rate. At a public fast charger you pay a much higher price for speed and convenience. The gap can be large, and it is repeated every month for as long as you own the car. But the saving only exists if you actually charge at home, and it has to repay the wallbox, the electrician and the small costs that come with them. This simulator turns that comparison into a monthly number so you can see whether the wallbox is a smart investment or an expensive ornament.
The structure of the problem is volume times a price gap, minus fixed costs. Distance and consumption set how many kilowatt-hours the battery needs. The share you charge at home decides how many of them get the cheap price. The gap between public and home price, adjusted for charging losses, is what each of those kilowatt-hours saves. The wallbox, its financing and standby power are fixed costs that do not care how many kilometres you drive. A high-mileage driver spreads them thinly and wins easily. A low-mileage driver may find the wallbox takes years to repay.
The domino cascade starts with the energy you charge at home. That energy multiplies the price gap to produce the gross saving. The fixed cost share then shows how much of the saving is eaten by the wallbox and standby, which determines the real cost per kilometre at home. The last box is the monthly saving. If you drive less, your tariff rises or your home share falls, the first box shrinks, the fixed share balloons and the result can turn negative even though home electricity is still cheaper per kilowatt-hour than the station.
The iceberg separates the bills you watch from the costs you forget. Above the waterline are the home electricity bill and the public charging you still use. Below it sit three costs that rarely appear in a comparison: the wallbox and installation spread over eight years, the energy lost as heat between the wall and the battery, which you pay for but never drive on, and the standby power and subscription of a connected charger. Use the simulator to find the distance, tariff or home share where the wallbox stops paying, then decide whether a simpler setup or a smarter tariff would serve you better.
Formula and methodology blueprint
The model works per month. The battery needs distance times consumption divided by one hundred kilowatt-hours. The home share of that energy is bought from the grid at the home tariff, with a loss on the way to the battery. The same energy would have cost the public price at a public charger, with a smaller loss. The saving is the avoided public bill plus a small allowance for the detours you no longer make, minus the home bill, the monthly cost of the wallbox repaid over eight years at 5%, and standby power.
- Battery energy
- E = km × kWh per 100 km ÷ 100
- How much energy the car takes in a month.
- Home bill
- H = E × home share ÷ 0.90 × home tariff
- Grid energy including about 10% charging loss, priced at your home tariff.
- Avoided public bill
- P = E × home share ÷ 0.95 × public price
- What the same energy would have cost at public stations.
- Wallbox cost
- W = annuity(wallbox cost, 8 years, 5%) ÷ 12
- The monthly share of the wallbox and installation over its working life.
- Monthly saving
- Net = P + detours − H − W − standby
- Positive means the wallbox pays for itself. The breaking point is where this reaches zero.
Cascading elasticity
Distance and home share move the result most because they scale the number of cheap kilowatt-hours. The public price and the home tariff act on the gap per kilowatt-hour, so a few cents either way matter. Consumption works like distance. Wallbox cost is a fixed charge, so it is a threshold rather than a slope: it matters little at high mileage and a great deal at low mileage.
Three real-world case studies
Bootstrapped starter
A city driver with a simple setup
A commuter who drives modest distances, charges mostly at home and installs a basic wallbox. The saving is positive but small, as the fixed cost takes a large bite. Loading it shows how mileage determines whether a wallbox is worth it.
Scaling mid-market
A high-mileage family or business driver
A driver covers three thousand kilometres a month, mostly on routes with expensive fast chargers, and charges at home on a cheap tariff. The wallbox repays quickly. Loading it shows how volume lifts the saving well above the base.
Black-swan crisis
A low-mileage driver with cheap public charging
Very few kilometres, a pricey installation, an expensive home tariff and a public network that happens to be cheap nearby. The wallbox never pays. Loading it shows which input would turn the month positive.
Industry benchmark matrix
| Metric | Danger zone | Industry average | Top 10% elite |
|---|---|---|---|
| Car consumption (real mixed driving) | Above 24 kWh/100 km | 16–20 kWh/100 km | Below 15 kWh/100 km |
| Public-to-home price ratio | Below 1.5 | 2.0–3.0 | Above 3.5 |
| Share of charging done at home | Below 40% | 60–80% | Above 85% |
| Wallbox payback period | Above 6 years | 2–4 years | Under 18 months |
| Wallbox cost as share of yearly savings | Above 100% | 40–70% | Below 30% |
Variables and levers
Distance per month
Kilometres you drive in an average month, including weekends and holidays.
Lever: If you drive little, consider a cheaper wallbox or a socket-based setup, because the fixed cost is spread over very few kilometres.
Consumption
Energy the car uses per 100 km in real mixed driving, not the brochure figure.
Lever: Smoother driving, correct tyre pressure and pre-conditioning while plugged in lower consumption, which reduces both home and public bills.
Home electricity tariff
What you pay per kWh at home, ideally the cheaper night or smart-charging rate you can really use.
Lever: Switch to an off-peak or smart-charging tariff and schedule charging for the cheap hours, because the home price is the whole advantage.
Public charging price
The average you pay at the stations you would otherwise use, with subscriptions and idle fees averaged in.
Lever: Track what you really pay at stations including subscriptions; if public charging is cheap for you, the wallbox has less to save.
Share charged at home
How much of your charging energy could realistically be delivered at home rather than at stations.
Lever: Plug in whenever the car is parked, since each extra share charged at home replaces the most expensive kilowatt-hours.
Wallbox and installation
Hardware, electrician, cabling and any consumer-unit work, after grants you are sure of.
Lever: Get several installer quotes, check grants and avoid an oversized unit; a simple wallbox does the same job for much less money.
How to use this simulator
- 1Enter your average monthly distance and the real consumption of your car.
- 2Enter your home tariff and the average public price you would pay at your usual stations.
- 3Set the share of charging you can realistically do at home and the installed wallbox price.
- 4Read the five domino boxes, then press Find my breaking point to see where the wallbox stops paying.
- 5Open the Parallel universe tab to compare your setup with a smart wallbox on an off-peak tariff.
Mistakes to avoid
- Assuming every kilowatt-hour is charged at home. Trips, holidays and busy days push charging to stations, so use a realistic share.
- Comparing the home tariff with the highest public price. Use the average you would really pay, including subscriptions and any cheaper local network.
- Forgetting charging losses. A tenth or so of the grid energy never reaches the wheels but still arrives on your bill.
- Ignoring the installation. Cable runs, consumer-unit upgrades and permissions can cost far more than the wallbox itself.
Frequently asked questions
Is a wallbox worth it?
It depends on mileage, the price gap and how much you charge at home. High-mileage drivers with a big gap repay it quickly; low-mileage drivers may not. Test your own numbers.
Why does the model include charging losses?
Some energy is lost as heat on the way from the wall to the battery. You pay for it but cannot drive on it, so it makes home charging slightly dearer than the tariff suggests.
Can I skip the wallbox and use a normal socket?
Often yes for low mileage, and it avoids the fixed cost. Check that the circuit and socket are safe for long charging sessions and ask a qualified electrician.
What if I have no home parking?
Then the home share is low and the model will show a small or negative saving. Workplace charging or a cheap local network may be the better plan.
Do tariffs and grants change?
Yes, often. Check current tariffs, public prices and grant rules before deciding, and update the inputs.
How accurate is this?
It is an educational planning model with stated assumptions, not financial or electrical advice. Compare it with your real bills and ask a qualified installer.
This is an educational planning model with stated assumptions. It is not financial, tax or legal advice. Replace the inputs with your own figures and verify important decisions with a qualified professional.