How to bill residents for EV charging

Why you end up paying for other people’s electricity

Chargers in an association’s garage or car park are usually supplied from the common-area meter. The association pays the energy bill, and its cost is spread across all units — including those without an electric car.

The problem arises when the chargers lack MID-certified submeters, which allow consumption to be measured reliably, as well as an access and charger management system. Without them, anyone can plug in a car, nobody knows who used how much energy, and the association has no grounds to charge the costs to unit owners.

The scale grows quickly: one electric car often uses 150–300 kWh a month. Five cars at 250 kWh each is 1,250 kWh, which at an energy cost of around 1 zł/kWh means over 1,200 zł a month that, without billing, is covered by all unit owners.

Illustrative calculation: the actual cost of 1 kWh depends on the association’s tariff and contract, and consumption depends on the number of cars and how they are used.

Three billing models compared

Associations usually use one of three models. With more than one charger, we recommend the last one — per-session billing: it is fair, scales with the number of cars and doesn’t burden the property manager with copying meter readings every month.

• Flat fee — a fixed monthly charge for each charger user. Simple to run, but unfair: someone who charges 50 kWh pays the same as someone who charges 500 kWh. As the number of cars grows, it quickly stops covering the costs.
• A submeter at a charger assigned to a unit — works when the charger is at a specific parking space. However, it requires manual readings, and with a shared charger it is impossible to tell who used how much.
• Per-session billing in a system — each session is assigned to a user, energy is metered in real time and the cost is calculated automatically. It works both for chargers assigned to units and for shared ones, with no manual readings.

In-house system or public operator

An association can hand its chargers over to an external charging network to manage or bill them in its own in-house system. At first glance, both do the same thing — meter energy and calculate charges. But they differ in who sets the rules and who keeps the money.

• Pricing: a public operator usually imposes its own commercial per-kWh rate, higher than the association’s energy cost. In an in-house system, the association sets the rate itself — equal to the actual cost of 1 kWh.
• Commission: the operator takes a commission on every kWh sold or a margin on the energy price. An in-house system costs a flat subscription, independent of consumption.
• Money flow: with an operator, residents’ payments go to the operator’s account first, and the association is reimbursed after the commission is deducted, often with a delay. In an in-house system, the amount due goes directly to the association — on the basis of a debit note.
• Access: public networks are geared towards serving any driver. In an in-house system, the association decides who can charge — only residents, specific units or selected chargers — and can revoke access at any time.
• Billing units: the operator settles with the driver, not the unit owner, so the association doesn’t get a per-unit report for its own billing. An in-house system provides reports assigned to units, ready for issuing debit notes.
• Data and contract: with an operator, user data and session history stay with the external company, and contracts are often multi-year. In an in-house system, the data belongs to the association and the subscription can be cancelled.

Why a public operator doesn’t pay off

The public operator model makes sense in a publicly accessible car park, where revenue from outside drivers is an end in itself. In a housing community, it works against residents: they pay a higher rate than the real cost of energy, and the difference goes to an intermediary instead of staying with the association.

Example: five cars draw a total of 1,250 kWh a month, and the rate for drivers is 1.50 zł/kWh. That is 1,875 zł a month. With a 20% commission, the operator keeps 375 zł a month, or 4,500 zł a year — and this amount grows with every additional electric car in the building. The Domena Power in-house system for 6 chargers costs a flat 80 zł net a month, regardless of the number of kWh.

Illustrative calculation: the commission and rates depend on the specific operator and contract, and consumption depends on the number of cars in the building.

MID meters and remote reading

Billing is based on knowing who started a session and how much energy they used. The charger communicates with the system via the OCPP protocol and sends energy readings, and the system assigns them to the logged-in user and unit.

Reliable billing requires chargers with MID-certified energy meters. Only then is the reading a credible basis for charging the unit owner, and it is easy to defend in the event of a complaint.

The second requirement is a convenient system, such as Domena Power, that collects readings remotely. The property administration doesn’t need to regularly visit the site and painstakingly write down meter readings — all the data is in the panel, assigned to specific units.

How to set the per-kWh rate

The rate for residents should correspond to the actual amount the association pays for 1 kWh. That way, nobody subsidises anyone else’s charging and the association doesn’t profit from residents. The rate is calculated from the bill for the meter that supplies the chargers.

• Add up all the components of the bill: active energy, distribution charges, the capacity charge and other variable charges, then divide by consumption in kWh. The gross result is the base cost of 1 kWh.
• If the association has a two-zone (day/night) tariff, set two rates in the system matching the prices on the bill — a cheaper night rate will encourage off-peak charging.
• Update the rate after every change in energy prices or distribution charges so that it still reflects actual costs.

How VAT is handled and how charging fees are documented depend on the association’s legal form and billing model — it is worth confirming this with your accountant.

An app, with RFID cards as an option

In the Domena Power system, residents start and stop charging in the app. They see the charging power, energy used and session cost in real time, and after the session ends — a detailed cost breakdown and full charging history.

The property manager doesn’t have to issue or replace RFID cards, although the system supports them if the community prefers cards. They add a new person remotely in the panel and can revoke access at any time, e.g. after a unit is sold, without a service visit.

Monthly billing step by step

With a system, billing comes down to downloading a report and issuing debit notes — no trips to the garage and no manual meter reading. The process looks like this:

• The system collects all sessions from the association’s chargers — with the date, duration, energy used and calculated cost.
• At the end of the period, the property manager downloads a report per user or unit from the panel: consumption in kWh, amount and number of sessions.
• On this basis, the property administration issues debit notes to unit owners for the energy used. We integrate with property administration and billing systems, including Betasi.
• Residents see the same data in the app as the property manager, so billing is transparent and doesn’t lead to disputes.

How much the billing system costs

The Domena Power subscription is 30 zł net (36.90 zł gross) a month for the first charger in a group and 10 zł net (12.30 zł gross) for each additional one. The first M2M SIM card, providing connectivity even in an underground car park, is included. We take no commission on energy — the entire amount from billing stays with the association.

Example: with 6 chargers, the subscription is 80 zł net (98.40 zł gross) a month, regardless of how many kWh residents use. You can calculate the cost for your site in the calculator below.