Skip to content

Frequently asked questions

  • Technical requirements
    • Can I install a solar PV system myself?
      The ready-made configurations of solar PV systems that we offer include connection diagrams that make their installation easy to perform by the customer. Off-grid systems, depending on their size, require basic knowledge of electrical engineering and their self-assembly is completely acceptable. It is important to follow the attached diagrams and instructions for installation and use of the separate components. In on-grid systems, the requirements for compliance with security conditions are slightly different. Relevant protocols and declarations of conformity by technical persons must be submitted for connection to the network.
    • What is the technical warranty of the solar PV modules ?
      The technical warranty of the solar PV modules, which we integrate into our solar PV systems is guaranteed by Munich Reinsurance Company:
      Гаранционен период на панелите
      A chart of the length of the warranty period of the CSUN solar PV modules
      The modules come with a 12-year technical warranty. Additionaly, there is a 12 year guarantee for maintaining 90% of the power capacity of the modules and a 20 year guarantee for 83% of their power capacity. The solar PV modules, which we integrate into our ready-made solar PV systems and the off-grid systems which we design come with a 10 year tehnical warranty and 25 years for maintaining 80% of their power capacity. Detailed information about the technical characteristics of the solar PV panels which we offer, can be found in our online store at
    • If the location does NOT have access to an energy source other than a solar PV system, can I use energy appliances with a power capacity larger than that of the system ?
      Not possible, unfortunately. It is for this reason that when calculating the power of an off-grid system, all electrical appliances, including their nominal power capacity and hours of usage, are taken into account. If you turn on a device that consumes more than the maximum power of the inverter, it will simply report an error and stop. If the overload is very high, there is a risk for the inverter fuse and even the inverter itself burning out.
    • I have a house and I would like to power it with solar energy entirely. How many solar PV modules do I need?
      With off-grid solar PV systems households rely entirely on the electricity they produce. These systems are most often used when there is no access to the grid or it is very expensive to connect to it. Or you aim to avoid the lengthy procedure that comes with getting connected to the grid. This type of solar PV system can have all kinds of power capacity. An off-grid system can power from a simple lamp to an entire production base. The sizing of off-grid systems is a complex process and depends on many factors. It depends on whether the system will be used all year round or seasonally. It depends on the power of the appliances, how many hours a day they will be used, the location of the system and many more. In order to calculate exactly what kind of off-grid system you need, you must first gather information about the appliances you will use and their unit capacities. Estimate how many hours a day they will work and then send us an inquiry so that we can offer you the best solution. Contact us for a free consultation.
    • Can I use a three-phase inverter with a single-phase grid?
      No, unfortunately, it is not possible to connect a three-phase inverter to a single-phase network. Only the opposite scenario is possible - connecting a single-phase inverter to a three-phase network. The three-phase inverter will not start without seeing three phases and a "zero". You could contact us for a free consultation.
    • How much will the efficincy of the solar panel decrease if it faces south-west, with a 40 degree slope?
      A specialized software is required to calculate the fall in efficiency at different orientations and at different inclines. It is also possible to calculate what the losses are and, accordingly, what the production will be if you change the slope or orientation of the solar PV panels. For this purpose, however, it is good to consult with experts in the field. You could contact us for a free consultation.
    • Is the application of steel possible for the mounting structure or does it have to be made from aluminium?
      Of course, the mounting structure does not have to be made entirely from aluminium. When we build our systems, we want to be sure that they will withstand a MINIMUM of 20 years in outdoor weather conditions. That is why we use only aluminum, galvanized and stainless steel for the supporting structure. Remember that building a solar PV system is a long-term investment and short-term savings usually lead to trouble.
    • Can a hybrid system be transformed into a battery-free off-grid system?
      The term "battery-free off-grid system" is a bit confusing, because a battery-free solar PV system can hardly be off-grid. That is, in the absence of batteries, it can only work when the amount of energy produced by solar panels is large enough to power the energy appliances. If there is no additional power supply from the mains or from a generator, the solar system becomes very unreliable. In our opinion, the answer to this question is rather NO, because we say again, the system would lose its autonomy.
    • How can I curtail the "excess" electricity from the inverter to the grid?
      The curtailment of "excess" energy to the main grid in most inverters is done by means of the so-called "smart" electricity meter or also known as a Smart Meter. Its function is to constantly monitor the consumption on site, whether it is a house, warehouse or a large production facility.The device transmits this information to the inverter 24/7. In this way, the inverter knows at any given point in time whether the amount of energy produced is greater than the amount consumed. It is when production exceeds consumption that this "excess" energy begins to return to the grid. If the inverter detects a situation in which the production is greater than the consumption, it immediately reduces its production so that it is equal to or less than the consumption of the site. In this way, the return of energy back to the EDC network is avoided.
    • What is the annual yield of a 5kW,10kW, 30kW solar PV plant?
      The annual yield of a solar PV system depends on a number of factors, including its location, whether it will be built on a rooftop or land, the slope and orientation of the property / building with regards to the sun. The figure below shows the estimated production of a ground-mounted solar PV plant with a capacity of 30kW, located in the region of Pazardzhik, with an ideal slope and orientation with regards to the sun. This system will produce 39,265.12 kWh per year. A system with a power capacity of 5kW will produce 6,544.19kWh under the same conditions, and a system of 10kW - 13,088.37kWh per year. In general, in Bulgaria, a power plant operates between 1200 and 1400 hours per year, depending on the region in which it is installed. That is, if it is 10kWp, at 1200 hours per year, it will produce about 12,000kW of energy per calendar year. месечно производство на слънчев енергия от 30kW система
  • Energy production
    • If I sign a PPA, the contract will be valid for 15 years, but feed in tariffs will be changed annually or will the tariff which was set at the time of contract signing be valid for the duration of the contract?
      The feed-in tariffs for solar PV energy are determined annually by a decision of the Energy and Water Regulatory Commission (EWRC) on July 1. The new tariff applies to all new investments in solar PV systems which are connected to the grid after this date. Its value is fixed for the term of the Power Purchase Agreement (until 2035). That is, at whatever price you sign a contract, it will remain the same until the end of 2035.
    • Is it possible for feed-in tariffs to be cancelled for solar PV systems up to 30kWp?
      The feed-in tariffs for the purchase of energy from solar PV systems are determined with a decision of the Energy and Water Regulatory Commission (EWRC) every year on July 1 and they are fixed for the term of the Power Purchase Agreement, but not longer than 31.12.2035. After this date, all solar PV plants start selling the electricity produced on the electricity market, as all power plants over 30kWp trade the produced energy at the moment. There are constant rumors about what will happen to preferential prices. Our advice is not to believe everything you hear, because the people who really know what will happen are very few and work in EWRC and do not have the habit of exporting such information.
    • What is the total value of the investment in a 30kW solar PV system and what are the associated monthly costs and revenues from the system?
      The value of the investment in a 30kW grid-connected solar PV power plant depends on a number of factors. It depends on the type of equipment, the location of the property, as well as the type of structure on which the panels will be mounted. Equipment costs also often change depending on supply and demand at a given time. At the moment we offer design, delivery of the equipment, construction and commissioning of 30kWp at a value between 40,000 and 45,000 BGN incl. VAT. The revenue from the investment depends mainly on the feed-in tartiff at which the respective Power Purchase Agreement has been signed. The tariff is determined with a decision of the EWRC every year on July 1. It is fixed for the term of the Purchase Agreement, but not longer than 31.12.2035. After this date, all solar PV plants start selling the produced electricity on the electricity market. As of 1-07-2021, the tariff for feeding energy from a power plant with a capacity of 5 to 30 kilowatts is BGN 160,11 per MWh (excl. VAT). By law, EDCs are required to purchase the entire amount of energy produced by these power plants until reaching 1 380 hours of annual system operation time. A 30kW system in Bulgaria produces between 35 and 40MWh per year, which is within the allowable production for purchase at a feed-in tariff. 0.03 x 1 380 = 41.40 mWh This production generates between BGN 6,000 and 6,500 per year for the investor. The revenue varies on a monthly basis, depending on the season and the intensity of sunshine in a given month. The only costs are fees and taxes on these revenues. The system does not require any technical support. It needs regular cleaning of the solar panels to ensure maximum efficiency in their operation.
  • Administrative process
    • Do I need to insure my solar PV system??
      The insurance of solar PV systems is an individual decision. If you have taken out a loan for the system, you will probably need to insure it. In general, you need to decide what the risks are and whether this will give you more peace of mind. For example, we rarely insure our systems. As far as we know, currently only Unica insures solar PV systems and power plants. Under the insurance "All risks of solar PV and thermal solar power plants" all types of solar PV and thermal solar power plants can be insured, owned by legal entities and individuals. The object of the insurance are operational technical facilities for electricity generation, thermal installations for water heating and other additional devices. The coverage is based on all risks. Any unforeseen or sudden loss, damage or damage to the objects or parts of them for any reason is subject to compensation, except for the risks excluded in the general conditions of the insurance.
    • I have my eye on a plot of land with a dilapidated house/ without a roof, with several dilapidated walls. If I manage to restore it with a few beams and a tin roof, and I find the lot number for electricity consumption, will it be legally eligible for solar PV system construction?
      For the construction of a solar PV power plant on a dilapidated house, you will most likely receive a grid connection refusal. Although it appears on the municipal plans, you need to bear in mind that a person from EVN does a site inspection and takes pictures of the property and buildings. That is, if the house is visibly dillapidated, it will not be recognized as a building. If you restore it so that it is intact, in our opinion, you will not have any problems.
    • How long does the administrative process take until commissioning of the solar PV plant?
      The administrative process related to the preparation for construction and connection to the network of a solar PV system with a capacity of 30kW takes about 6 months. This period may vary depending on the requirements and deadlines set in the specific Municipal Administration and EDC. Our many years of experience with these procedures helps us assist clients during every step of the process.
    • Which are the active EU Programmes for funding of solar PV systems at the moment?
      Currently, an active EU Programme is Measure 4.1 of the RDP, related to investments in agricultural holdings. Eligible applicants are farmers with a minimum of 36 months of history and SPO of at least 8000 euros and systems only for their own consumption! BUT the solar PV systems are only eligible as a supplement to the main project, which must be related to agriculture or animal husbandry. There are no programs and in the last 7-8 years there have not been any that would finance only the solar PV system as a separate project.
    • Is it possible to insure a solar PV system without a security system installed at the site? Could you recommend an insurance company?
      As far as we know, currently only Unica insures solar PV systems and power plants. Can it be done in the absence of an alarm system? It is most likely possible, but with a higher insurance premium.
    • Is it possible for a solar PV system to be connected to the grid on the basis of an existing garage structure?
      According to Art. 24 of the Renewable Energy Sources Act (ZEVI, amended SG No. 21 of 12 March 2021) the construction of a solar PV plant with a total installed capacity of up to 30kW is possible “on roofs and façade structures of buildings connected to the electricity distribution network and on real estate adjacent to them in urban areas ”. In our many years of experience, it is sufficient to have a building in the property, which is reflected in the municipal plan and to have an active account for electricity consumption with the local EDC, in order to be eligible for connecting a solar PV plant to the main grid.
    • How long does it take to receive a construction permit for a solar PV plant?
      The construction permit for a solar PV power plant with power capacity of up to 200kW is issued on the basis of an approved technical project. This is possible only after approval of the project by the EDC and the Municipal Administration of both the structural part and the electrical part of the designs. The process from the approval of the project to the issuance of the construction permit takes about one calendar month. The steps from the administrative process to the preparation of a technical project, including obtaining a position document for connecting to the grid by the EDC, in turn, take 1-2 months. Variations are possible depending on the specific requirements and deadlines of the local municipal administration and the local EDC.
    • Is it true that the administartive procedure for connecting a 10kW solar PV system to the grid is the most simplified?
      The duration and administrative burden of the procedure for connecting a solar PV system to the respective electricity distribution company (EDC) depends mainly on the purpose of the produced energy. For on-grid systems up to 30kW, where the energy will be used for own consumption, the procedure is the shortest and easiest. It is usually about 4-5 months depending on the requirements of the specific EDC. If the produced energy is intended for sale at a tariff, the process is extended by 1-2 months. This is due to the need for an additional step upon request for a Power Purchase Agreement. The tariffs for energy from solar PV power plants, which are determined by the EWRC by July 1 of each calendar year, are divided into two categories: up to 5kW inclusive, installed on roofs and facades, and from 5 to 30kW inclusive, installed on roofs, facades and land. There are no special preferences for roof power plants up to 10kW either in terms of purchase price or in terms of the administrative process. There was only discussion of such relief, but no action was taken with regards to legal changes.
    • Is it possible to build a 30kW solar PV system entirely on agricultural land?
      • According to the Renewable Energy Sources Act (ZEVI) solar PV power plants up to 30kWp enjoy preferences regarding the administrative process of grid connection and tariff only in the cases when it is envisaged that they will be installed on rooftops and facades of buildings connected to the electricity distribution network and on the land adjacent to them in urban areas.
      Theoretically, it is possible to build a power plant on agricultural land, but only when it falls within the scope of the pre-approved capacity by region (Article 22, paragraphs 1 and 2) and is not under Article 24, item 1 (power plants up to 30kW). At the same time, such an investment is meaningless, unless it is large (over 500kW), because the energy will not be bought at a tariff and will have to be traded on the electricity market.
    • Is it possible for the EDC to refuse connecting my solar PV system to the grid?
      The legal framework and conditions are different depending on the power capacity of the solar PV plant and the purpose of the energy which it produces. Usually the plants are built either to cover their own needs or to sell electricity at a tariff. According to the Renewable Energy Sources Act (ZEVI), the operator of the electricity transmission grid have the right to the so-called "Motivated refusal" to connect a solar PV plant only in two cases. One is when the required power is over 200kW, and the second when it will be built to sell the produced electricity. They may refuse connection on the basis of exhaustion of the approved electrical connection capacities determined for the respective region (Art. 23, item 6). This provision does not apply to energy sites for production of electricity from renewable sources under Art. 24 of ZEVI, namely:
      • solar PV systems with a total installed capacity of up to 30kW, which are planned to be built on roof and facade structures of buildings connected to the electricity distribution network and on real estate adjacent to them in urban areas;
      • solar PV systems with a total installed capacity of up to 200kW, which are planned to be built on roof and facade structures of buildings for production and storage activities connected to the electricity transmission or distribution network in urban areas;
      • for solar PV systems, when when submitting a request for connection, the investor declares that they will not take advantage of the tariffs for the produced energy.
      These categories of solar PV systems join the network with priority and enjoy simplification of the administrative process. In other words, regional operators have no legal basis to refuse their connection to the grid, as they fall outside the scope of pre-approved regional capacities (Article 22, paragraphs 1 and 2). The conditions for connection of these systems to the grid are determined within 2 weeks from the submission of a request to the respective EDC. In short, in the presence of a positive response from the EDC, in the subsequent steps, there is no way to refuse the purchase of the energy produced by the solar PV system.

Got questions? Contact us!