A useful charging log needs only four columns: the date, the energy added in kWh, the price you paid per kWh, and a short note on what the charge was for. Most of those numbers already exist in your charger app and on your utility bill — the log simply joins them in one place. This article is about record-keeping, not tax advice: what a tax adviser or an employer will ask for varies, and they are the people to confirm it with.
Key Takeaways
- Four fields are enough: date, kWh, price per kWh, and a purpose note.
- The app and the utility bill already hold most of it — a monthly five-minute routine joins them up.
- Use your own bill’s rate; the 18.31 cents/kWh EIA average is an estimate, not your price.
- Keep installation documents with the tax records for the year they relate to, and let your tax adviser set retention.
What to Record, and Where It Comes From
| Field | Where it comes from | Why it is there |
|---|---|---|
| Date and start time | Charger app session history | Places the charge in the right billing and tax period, and in the right off-peak window. |
| Energy added (kWh) | App, wallbox display, or car | The quantity everything else is calculated from. |
| Price per kWh | Your utility bill or tariff schedule | Turns kWh into money. The U.S. residential average is 18.31 cents/kWh (EIA) — an estimate only; your bill’s rate is the better number. |
| Session cost | kWh × price | The figure an employer reimbursement or a household split actually uses. |
| Note: personal, work, or shared | You | The split is the part no device can record for you. |
If working out what share of a bill belongs to the car is the problem, our guide to the cost of charging an electric car at home covers the arithmetic behind these columns.
Why People Keep One
- Employer reimbursement. If you charge a work vehicle — or your own car used for work — at home, an employer will want dated kWh figures, not a guess. A session log is exactly that evidence.
- Household splits. Where a charger is shared or a tenant reimburses a landlord, the log is the neutral record both sides can check.
- Tax-time records. If your tax adviser asks what home charging cost, or you claimed something for the installation itself, the log plus the installation file is the answer. Our overview of charger installation and tax deductibility explains the questions to take to that adviser.
Installation paperwork matters here too. The Section 30C credit, for example, applied to property placed in service between January 1, 2023 and June 30, 2026 — so for a return covering that period, the invoice, permit record and proof of the property’s location belong with that year’s documents. Your tax adviser sets how long to keep them; the IRS page on the 30C credit states the terms.
A Five-Minute Monthly Routine
- Export or screenshot the month’s session history from the charger app before it rolls over.
- Note the rate from that month’s utility bill, including which sessions fell in an off-peak window.
- Add the purpose note while you still remember which trips were work.
- Save the file with the month’s bill, so the two halves of the record stay together.
Equipment That Logs for You
A smart wallbox removes most of the manual work: sessions are recorded automatically with dates and kWh. The EV-ACT3204PE is a 22 kW three-phase wallbox with app control and RFID, so different drivers’ sessions can be told apart — useful when a household split or a work claim depends on who charged. You still add the price per kWh and the purpose note yourself.
Frequently Asked Questions
My app already records every session. Do I still need a log?
The app history is the log’s raw material, but export it regularly: accounts change, apps are replaced, and an export with your bill and your purpose notes is what an employer or adviser can actually use.
Can I just use the national average electricity price?
Only as a clearly labelled estimate — the EIA residential average is 18.31 cents/kWh. Your own bill’s rate is more accurate and just as easy to record once a month.
How long should I keep a charging log?
Ask your tax adviser if taxes are the reason, and your employer if reimbursement is — they set the requirement. Keeping the log with the matching utility bills, for as long as you keep those bills, is a sensible default.
Related Reading
- How Much Does It Cost to Charge an Electric Car at Home?
- Is EV Charger Installation Tax Deductible?
- Wallbox Home Charger Installation Guide 2026
