Running a solar IPP in Hungary: five operating decisions and the data behind each

A solar independent power producer (IPP) owns solar parks and sells their power. Its results turn on five operating decisions: when to curtail, how to schedule, how to maintain, how to enforce availability and warranties, and how to hedge and report. This is a general framework as of October 2026. It does not describe how any one company decides.

What is a solar IPP?

A solar IPP is an independent power producer that owns and operates solar parks and sells the electricity they generate. It is not a utility that also runs the grid or supplies households. Its revenue comes from support schemes, market sales, power purchase agreements (PPAs) or a mix. The comparison of METÁR, METÁROLÓ and KÁT covers the Hungarian support schemes. SolServices, a Budapest solar IPP, lists its parks on the portfolio page.

What are the five decisions, and what does each depend on?

Each decision turns a data stream into money. The table shows the data, a typical review rhythm and the financial lever for each. The rhythms are typical practice, not rules.

When should a solar park curtail during negative prices?

A park should curtail when the price it would receive for an interval is below the cost of producing it, after counting any support payment it would lose. In Hungary the answer depends on how the park sells.

Negative intervals are frequent enough to matter, and the capture rate article has the counts. The decision runs on the day-ahead price of HUPX, the Hungarian Power Exchange, which it publishes in quarter-hour steps, 96 per day.

Three cases apply:

• Market-exposed parks. A negative price means the park pays to deliver, unless it curtails or sells under a contract that ignores the spot price.
• Premium-supported parks. No premium is paid for output in the negative-price units that section 15(4) of Decree 299/2017 counts, which depends on a run of at least six consecutive negative units. Check the unit length in the offtaker's rules. The METÁR comparison linked above explains the premium and how the unit length is read, and the consolidated decree has the full text.
• Grid-ordered reductions. These are not a price decision. Under Regulation (EU) 2019/943, Article 13, redispatch must use market-based mechanisms with financial compensation. Non-market redispatch is allowed only in listed cases, such as when no market-based alternative is available.

A simple decision routine has three steps:

1. Identify which rule governs each park: the support scheme, the sales contract, or both.
2. Compare the expected interval price with the support payment that would be lost.
3. Log curtailed MWh and the cause, economic or ordered, so that compensation claims and revenue analysis use the same record.

Who bears a negative interval under a PPA depends on its type, which the article on pay-as-produced and pay-as-nominated PPAs explains.

How do scheduling, nominations and imbalance costs work?

A solar park sells a forecast, and the gap between forecast and actual output is settled as imbalance. Regulation 2019/943, Article 5(1), states that "all market participants shall be responsible for the imbalances they cause in the system". In practice this runs through a balance responsible party (BRP), and a schedule (also called a nomination) is the forecast the BRP submits.

MAVIR, the transmission system operator, publishes the list of valid BRPs, the interface specification for BRPs and mandatory-purchase balance group members, and the schedule file template. Producers under the KÁT scheme have scheduling duties and a surcharge for deviations of their own, which the METÁR comparison covers.

The imbalance price follows MAVIR's methodology:

• Hungary has applied single imbalance pricing since 1 January 2022.
• The price depends on the system direction. Its base is the volume-weighted average price of activated balancing energy, and the methodology adds an incentive element that references the HUPX day-ahead clearing price.
• MAVIR said the rules had to be redesigned for access to the European MARI and PICASSO platforms, with the new model applying from the business day of 1 October 2026 (network code version 3.1.35, approved by the regulator MEKH on 1 July 2026 and revised on 26 August 2026).
• In its update of 20 June 2026, MAVIR said it had not submitted the network code amendment that would bring a scarcity surcharge into effect.

Earlier patterns may not carry over. Montel reported in March 2024 that the system was long in 80% of quarter-hour settlement periods across seven consecutive months, in a trend that began in the fourth quarter of 2022. That predates the redesign.

Forecast quality drives the result. The International Energy Agency's Photovoltaic Power Systems Programme (IEA PVPS) notes that PV forecasting can be offered by the O&M contractor or an outside provider, and that the choice can affect contracts with trading partners. Points to settle include who acts as BRP, which forecast provider is used, how often the schedule is updated, and how imbalance cost passes through the sales contract.

How should O&M, cleaning and vegetation management be decided?

Each round of cleaning, mowing or inspection pays when the energy it recovers, valued at the price the park captures, exceeds its cost. The price part matters, because the capture rate determines what a recovered kilowatt-hour is worth.

The IEA PVPS Task 13 guidelines list the common preventive maintenance actions: periodic module-level electrical sampling, infrared inspections, cleaning, site and vegetation management, upkeep of inverters and trackers, and upkeep of monitoring systems. On vegetation and soiling the report says:

• Grass or plants growing next to arrays can shade them and cause hot spots.
• Where mowing is needed, there is a risk of projectiles damaging modules, and grazing animals in cooperation with local farmers have gained popularity.
• For temperate climates, it advises an on-site evaluation of vegetation, wildlife and farm animals, and combining grass cutting with a module inspection to decide whether cleaning or repairs are needed.
• Cleaning should follow the equipment maker's recommendations, with plain demineralised water and mild detergents.
• Soiling should be measured locally to optimise cleaning schedules.

On cost, the same report gives typical base O&M costs, including soiling mitigation, of EUR 6.5 to 16.5 per kWp per year. This is a global range, not a Hungarian price. It also recommends that owners set aside maintenance reserve accounts for replacements. The best practices guide from the US National Renewable Energy Laboratory (NREL) argues that standard O&M planning makes costs more predictable, which helps financing.

How do availability guarantees and warranty claims protect output?

O&M contracts guarantee plant availability, and the owner protects output by checking inverter-level data against the contract definition. IEA PVPS says guaranteed plant availability is the second most common O&M guarantee after performance ratio, and that most good-practice guidelines recommend at least 99%.

The definition decides the result:

• Time-based availability is the share of time the plant produces, using inverter-level data and a production window. IEA PVPS suggests an irradiance threshold, with a minimum of 30 W/m2 usually a good approach.
• Energy-based availability uses the reference yield, so it shows the energy lost while unavailable. The time-based method is used more often because its input data comes straight from inverter monitoring.
• Plant-level availability excludes the grid, which is outside the O&M operator's control.

The report recommends using the performance ratio guarantee and the availability guarantee together. It also describes response-time guarantees, with critical events needing immediate action and major events a response within a day or two. Neither availability measure weights lost hours by price, so the owner's own analysis has to add that.

Warranty handling sits in the same contract. IEA PVPS lists "equipment warranty and claim management" among common O&M scope items. It also says to specify warranty periods for replaced components and who owns spares, and it warns that module makers' recommendations must be followed to avoid loss of warranty. Infrared inspections are used for end-of-warranty checks. The decision is which faults to claim on, and when to inspect before a warranty runs out.

How should a solar IPP hedge, and what should it report?

An IPP hedges by deciding how much output sits on fixed or supported prices and how much on market prices, then reports the realised result against budget on a fixed schedule. The tools are support schemes, PPAs, forwards and storage.

Solar output tends to sell below the market average, so a hedge priced on an average price does not lock in the revenue of solar output. The capture rate article measures that gap. PPA structure decides who carries it, as the pay-as-produced and pay-as-nominated comparison shows. Storage changes the exposure by moving output out of weak hours, and the article on the battery storage revenue stack covers that case.

For lenders and owners, the NREL guide recommends solar asset transparency for investors and rating agencies. A monthly pack usually draws on the data from the other four decisions:

1. Generation against budget.
2. Availability and open warranty claims.
3. Realised price and capture rate.
4. Imbalance cost per MWh.
5. Curtailed MWh by cause.
6. O&M spend against budget.

What this means for solar park owners, investors and corporate buyers

The five decisions share data, so they are best run as one process.

• Park owners can start by mapping which rule governs each park in negative-price intervals, and by checking that the availability definition in the O&M contract matches the inverter data.
• Investors and lenders can ask for the monthly pack above and for curtailed MWh split by cause, because ordered and economic curtailment have different compensation rights.
• Corporate buyers under a PPA should check which party carries negative-price intervals and imbalance cost, since the contract type decides it.
• All three should treat imbalance history before 1 October 2026 with care, as MAVIR changed the settlement model from that date.