Single-phase or three-phase connection? Differences, costs and when to choose each
Single-phase or three-phase connection: the quick answer
The essential difference lies in the voltage and the available power: a single-phase connection operates at 230V and covers an approved power typically around 8-11 kW, sufficient for an ordinary home. A three-phase connection operates at 400V between phases, distributes the load across three conductors and allows for much higher power, making it necessary for heat pumps, professional cooking ranges, fast EV chargers or machinery with three-phase motors.
At SUN WATT SRL (bransam.ro), a company certified by ANRE for execution and design of electrical connections (bransamente) in Bucuresti, Ilfov and Giurgiu, indicative prices start from 1,800 lei for single-phase and 2,900 lei for three-phase. For an estimate tailored to your project, use the connection cost calculator or request a quote via contact. Tel: 0733 097 440.
What single-phase and three-phase actually mean
The single-phase connection (230V)
A single-phase connection brings energy through a single phase conductor plus neutral. It is the standard solution for most individual homes, apartments and small premises. All ordinary household appliances (fridge, washing machine, electric oven, boiler, sockets, lighting) work without any problems on single-phase.
The main advantage is the lower cost and the simpler installation. The disadvantage appears when simultaneous consumption rises significantly: at high power on a single phase, the risk of imbalance and tripping of protection devices is higher. See details on our single-phase connection page.
The three-phase connection (400V)
A three-phase connection brings three phase conductors plus neutral, with a voltage of 400V between phases and 230V between phase and neutral. This means you can distribute the load across three circuits, obtaining a significantly higher total available power without overloading a single phase.
Three-phase is mandatory or strongly recommended for: high-power heat pumps, fast EV charging (three-phase wallbox), workshops with three-phase motors, industrial air-conditioning systems, lifts, warehouses and commercial premises. Full details on the three-phase connection page.
Comparison table: single-phase vs three-phase
| Criterion | Single-phase connection | Three-phase connection |
|---|---|---|
| Voltage | 230V (phase + neutral) | 400V between phases / 230V phase-neutral |
| Conductors | 1 phase + neutral | 3 phases + neutral |
| Typical approved power | approx. 8-11 kW | from ~11 kW upwards |
| Load balancing | everything on one phase | spread across 3 phases |
| Recommended use | homes, apartments, standard consumption | heat pumps, wallbox, motors, workshops, warehouses |
| Compatibility with three-phase motors | no | yes |
| Indicative cost (from) | 1,800 lei | 2,900 lei |
| Installation complexity | low | medium-high |
The power values are indicative; the actual approved power is set through the ATR (Technical Connection Approval / Avizul Tehnic de Racordare) issued by the distribution operator Retele Electrice Romania S.A. (formerly E-Distributie/Enel).
When to choose single-phase
A single-phase connection is the right choice if:
- You are building or connecting an individual home with ordinary consumption.
- You have no appliances or machinery that require a three-phase supply.
- The total requested power typically falls below ~11 kW.
- You want the lowest execution cost and a simpler dossier.
For an ongoing construction site, there is also the option of a temporary construction-site connection, with indicative prices from 2,200 lei.
When to choose three-phase
You opt for a three-phase connection if:
- You are installing a high-power heat pump or several sources of consumption running simultaneously.
- You want fast EV charging through a three-phase wallbox.
- You have a workshop, warehouse or commercial space with three-phase motors or equipment.
- You anticipate high consumption and want to avoid phase imbalances.
- You are planning future extensions of the installation.
Even if your consumption is currently modest, if there is a chance you will later add a heat pump or an EV charging station, three-phase saves you a costly upgrade down the line.
How much it costs and what the final price depends on
SUN WATT SRL indicative prices:
| Type of work | Indicative price (from) |
|---|---|
| Single-phase connection | 1,800 lei |
| Three-phase connection | 2,900 lei |
| Underground connection | 3,500 lei |
| Temporary construction-site connection | 2,200 lei |
| DIU (documentation, excluding labour) | 1,200 lei |
| Connection dossier | 900 lei |
The final price depends on several factors: the distance to the existing grid, the type of routing (overhead or underground), the approved power, any additional works and the technical solution in the ATR. The DIU (Utilisation Installation Dossier / Dosarul de Instalatie de Utilizare) documentation is usually required and carries a separate cost, from 1,200 lei, excluding labour.
See the full list on the prices page or get a quick estimate with the cost calculator.
How the grid connection works
- Determining the power and the type of connection (single-phase / three-phase) based on your consumption.
- Preparing the connection dossier and submitting the application to Retele Electrice Romania S.A. (from 900 lei).
- Obtaining the ATR, which confirms the approved power and the technical solution.
- Execution of the connection by an ANRE-certified company such as SUN WATT SRL.
- Energisation after checks and the installation of the meter.
SUN WATT SRL is ANRE-certified both for execution and for design, and issues the DIU nationwide. We thus manage the entire process, from documentation through to energisation.
Conclusion
If you have a home with standard consumption, single-phase (from 1,800 lei) is sufficient and cheaper. If you have high consumption, three-phase equipment or expansion plans (heat pump, wallbox), three-phase (from 2,900 lei) is the right long-term investment. The exact power and technical solution are confirmed through the ATR.
Not sure which one suits you? Call 0733 097 440 or write to us via the contact page and we will recommend the optimal solution.