Choosing a Photovoltaic System for Your Home in Romania

Choosing a residential photovoltaic system involves more variables than most homeowners initially expect. The decisions made at the specification stage — system size, panel type, inverter architecture, mounting method — determine yield, reliability, and long-term maintenance cost for the next 25–30 years. Getting them wrong at the start is far more expensive than taking the time to understand them.

This article covers the main specification decisions for a residential system in Romania, the criteria for evaluating components, and the questions worth asking before signing a contract with an installer.

How much capacity does a household actually need?

The most common sizing error is specifying a system based on the maximum available roof area rather than on the household's actual consumption profile. Oversizing wastes money; undersizing means a lower self-sufficiency rate than expected.

Starting with consumption data

The starting point is 12 months of electricity bills, which should show monthly consumption in kWh. For most Romanian households, annual consumption falls between 2,800 and 5,000 kWh/year. Households with electric water heating, underfloor heating, or a heat pump will be at the upper end or above it.

A rough rule for south-facing installations in southern Romania: 1 kWp installed produces approximately 1,200–1,450 kWh/year. A 4,000 kWh/year household could theoretically cover its full consumption with 3–3.5 kWp — but since the system will produce mostly during daytime and the household may not be at home to consume it, a larger system with battery storage or a grid-export strategy is typically specified.

The self-consumption vs export trade-off

Under Romania's prosumer billing rules (ANRE Order 228/2021 as amended), exported electricity is compensated at a rate set periodically by ANRE — generally 60–70% of the consumption tariff. This means exported energy is worth less than consumed energy. A system sized to match daytime consumption (or to fill a battery) is financially more efficient than one sized to maximise export.

A practical approach: size the system so that peak production in June does not exceed 150% of average daytime household load, unless the economics of export compensation clearly support it. For most Romanian tariff structures in 2024–2025, they do not.

Roof assessment: what to check before getting quotes

Orientation and tilt

A south-facing roof at 30–35° tilt is optimal for annual yield in Romania. West and east orientations lose approximately 15–20% of annual yield compared to due south. North-facing sections should not carry panels. A roof tilted at 15° will produce around 5–8% less annually than one at 30°, and will accumulate more soiling and be slower to shed snow.

Available area and structural assessment

A standard 400 Wp monocrystalline panel measures approximately 1.0 × 1.7 m (1.7 m²). A 6 kWp system requires 15 panels = 25.5 m² of unobstructed, structurally adequate roof. Common obstructions — chimneys, skylights, vent pipes, dormer windows — reduce usable area and can create shading on adjacent panels if not accounted for in the layout design.

The roof structure should be assessed for its capacity to carry the additional load of the mounting system and panels (typically 15–25 kg/m²). Older rural properties in Romania may have timber roof structures that require reinforcement. Any reputable installer should carry out a visual structural assessment as part of the site survey.

Roof covering and attachment method

The roof covering type determines the mounting hardware. Common Romanian roof types:

• Ceramic or concrete tile: Tile hooks are inserted under individual tiles. Standard approach for most residential systems in Romania.
• Metal sheet (tabla): Seam clamps or penetrating mounts with EPDM seals. Common on rural and agricultural properties.
• Flat bitumen membrane: Ballasted (weighted) mounts with no penetration, or low-angle penetrating mounts with flashing. Used on flat-roof residential properties in urban areas.

Component selection criteria

Panel manufacturer tier and warranty

The Bloomberg New Energy Finance tier classification — while not an industry standard — is widely used as a shorthand for manufacturer financial stability. Tier-1 panels from manufacturers with a track record of honouring warranty claims are preferable to cheaper unclassified units, given that the 25-year output warranty is only as good as the company that issues it.

Romanian consumers have documented warranty claim difficulties with several Chinese manufacturers that exited the European market between 2018 and 2022. Sticking to manufacturers with established European distribution and service presence reduces this risk.

Inverter choice: string vs microinverter

For a simple, unshaded, south-facing roof, a string inverter from a reputable brand (Huawei, Fronius, SMA, SolarEdge, GoodWe) is adequate and cost-effective. String inverters have a typical lifespan of 10–15 years; budget for a replacement mid-system-life.

If the roof has sections facing different directions, or if shading is expected at any point during the day, microinverters or a DC optimiser system (SolarEdge) can recover 10–25% of lost yield. The higher upfront cost needs to be weighed against the yield improvement specific to the site.

Monitoring

All grid-tied inverters sold in Romania for residential use include monitoring via manufacturer apps. The data logged — yield, grid export, inverter temperature, fault codes — is essential for detecting underperformance early. Set up monitoring before final sign-off and confirm the data matches expected figures within the first week of operation.

Evaluating installers

The quality of the installer is the single factor most within the homeowner's control. Equipment differences between mid-tier and top-tier panels represent a few percentage points of yield; installation quality differences can affect yield, safety, and durability far more significantly.

AFM registration

For Casa Verde programme eligibility, the installer must be registered on the AFM list of authorised operators. This list is public and searchable on the AFM website. An installer not on this list cannot issue a valid invoice for grant reimbursement.

ANRE authorisation

Installers carrying out electrical work must hold an ANRE Type B or C electrical installer authorisation. Verifying this takes two minutes on the ANRE website and confirms the person signing off on the electrical installation is legally authorised to do so.

References and documented installations

Ask for references from installations completed in the past 12 months, ideally in similar roof conditions. A credible installer will be able to provide SCADA or monitoring screenshots showing real production data from comparable systems in the same region.

Common specification mistakes

• Over-specifying string size: Connecting too many panels in series can push string voltage above the inverter's maximum input voltage on cold winter mornings (when module Voc is highest). This is a safety issue that also voids inverter warranty.
• Ignoring cable sizing: Undersized DC cables cause resistive losses and, in extreme cases, fire risk. All cable sizing should comply with IEC 60364-7-712.
• Skipping the DNO pre-notification: The DNO technical feasibility study must be completed before installation begins. Installing first and applying later puts the prosumer agreement at risk if grid constraints are discovered post-installation.
• No surge protection: Romania's electrical distribution grid experiences more voltage surges than Western European grids. DC and AC surge protection devices (SPDs) are not optional.
• Assuming the grant covers battery storage: The Casa Verde programme as of 2024–2025 does not include battery storage in the eligible cost. Batteries are an out-of-pocket cost.

After installation: what to expect in the first year

New installations in Romania typically show a 2–5% below-expected yield in the first three months. This is normal and reflects the initial break-in of panel encapsulant and the calibration of inverter MPPT algorithms. Output stabilises by month three to six.

Monitor monthly yield against the P50 estimate provided by the installer (this should be in the quote documentation). A deviation of more than 10% below P50 in a month with normal weather warrants an investigation — common causes include an MPPT fault, loose DC connector, or unexpected shading from a new structure or vegetation.

Related reading: How Solar Panels Work in Romanian Conditions • Solar Panel Installation Costs and Subsidies in Romania