Frequently asked questions - Photovoltaics

1. What is worth knowing about installing photovoltaics?

Installation is handled by our qualified and experienced team of professionals, including automation specialists, roofers and electricians.  Our company PROWABLE sp. z o.o. offers the best quality installation and consultancy services so that you will not have to worry about anything. First, we prepare an offer for the customer, then we proceed with the design and installation of photovoltaic panels. 

PROWABLE sp. z o.o. has a third-party insurance policy so that the investor can be sure that in case of any damage, the insurance company will cover the repair costs.


During installation, our fitters make only as many holes in the roof sheathing as necessary to properly install the photovoltaic system on the roof, and they do it in a professional manner so that you do not have to worry about possible leaks. 


2. What type of roof for photovoltaic panels?

Photovoltaic panels can be mounted on any roof covering. 


If the customer is just building a house or planning to replace the roofing, it is worth thinking before buying materials. Because if you cover most of the roof with photovoltaic panels, it is a pity to waste on expensive roofing, which will be covered anyway.


It is more economical to put much cheaper roofing under photovoltaic panels.

3. What kind of information do we need to install photovoltaic panels on your home?

We need some basic information from customers:


  • How much electricity they currently use (this is best illustrated by annual consumption)
  • Who is the operator of the electricity network that the customer uses.
  • What is the structure of the roof, and what is the roof covering.


The best place for installation is on the south and west sides, which get the most sunlight. This is why we ask clients to provide photos of the roof slope on which the installation is to be made. The customer can send us all the necessary information or contact our advisor who will come to the place, take photos of the roof and write down all the data needed to create an offer.

4. What do I need to prepare for the installation of photovoltaic panels?

If you are building a house, on which you want to install photovoltaic panels, leave a groove or a hole to hide cables from the photovoltaic installation.


In older buildings, our fitters, before starting work, agree with the customer the most convenient way to lead the cables and the place for the inverter.

5. What is Photovoltaics?

PV stands for photovoltaics or photovoltaic. Photovoltaic panels convert the sun’s free rays into direct current. The energy is then sent to an inverter (or inverter). The inverter converts the energy into alternating current – the one you use in your home.

6. What power installation do I need?

The power an installation should have can be estimated in several ways. In the case of a house that you have used for many years, you only need to give us your monthly energy consumption and electricity bills. 


On the other hand, if you are just building a house, you should consider what electrical appliances you will use in the future. Then we will estimate how much electricity you will use and what kind of power you will need.


If you plan to use electricity to heat your home using, for example, heating films, then you will need to have a thermal performance certificate for the building. This is necessary in order to estimate your full energy consumption.

In addition, one year after the installation has been put into operation, we check how well these estimates have been confirmed. It is often the case that people who were saving energy no longer pay attention to this after the installation. And the amount of electricity they consume has increased significantly.

7. Does photovoltaics on a new house make sense?

Of course you can! It does not matter whether you want to install a photovoltaic system in a new or old house. In the case of houses that have been used for many years, we only need the electricity bills to estimate the power of the panels.


On the other hand, if you are just building a house, you need to think about which electrical appliances you will use in the future. Then estimate how much electricity you will use and what wattage you will need.


If you plan to use electricity to heat your home using, for example, heating films, then you will need to have a thermal performance certificate for the building. This is necessary in order to estimate your full energy consumption.

8. What is the efficiency of photovoltaic panels?

The efficiency of photovoltaic panels is the amount of electricity they are able to produce. More and more efficient modules are appearing every year. Back in 2017, the panels were around 300 watts. Today, Prowable sp. z o.o. offers 390 W modules as standard, which are similar in size to those in 2017. 


The more powerful the panel, the greater its efficiency. Consequently, the amount of energy it can produce is greater.

9. Is it worth installing the system before moving into a new house?

Yes, it is worth it. However, we approach the matter individually. If the customer is afraid of burglary or vandals, then it is better to hold off on the installation. It is best to carry out the installation shortly before or just after the move.

10. What is in the PV project?

We prepare an individual offer for each customer, in which we precisely calculate the cost of installation and how quickly the investment in PV will pay off. We also specify the scope of the service (design, installation, connection of the installation to the power grid).


Once the offer is accepted, we prepare a project which we deliver to the grid operator. The installation design includes information on the type and power of photovoltaic panels and the type of inverter or microinverters.

11. Do photovoltaic panels produce electricity in winter?

Photovoltaic panels also produce electricity in winter, but with lower efficiency, due to weather conditions.


In the winter months, the sun is further away from the earth, the angle of the sun’s rays is also different than in summer. And the days of sunshine are much shorter and shorter than in June, July or August.

12. Does photovoltaic installation on the ground pay off?

Regardless of the type of substrate, a photovoltaic installation always pays off, as it pays for itself after a longer or shorter period of time. In addition, this way of generating electricity does not pollute the environment.


The most important thing is to design the installation so that it works in the most efficient way. The panels must be fixed to the frame at the right angle and positioned so that as much sun as possible falls on them during the day.

13. PV insurance - is it worth it?

An insurance policy protects the insured against damages incurred. Micro installation insurance has become a standard in policies over the last year. When contracting with an insurer, you have to increase the value of the property by the price of the photovoltaic kit. PV insurance can cover damage to panels caused during heavy hail, fire, windstorm, storm or other random event. Depending on the type of policy and insurance company, the customer can also expect compensation if the installation does not work for a longer period of time and he suffers financial losses as a result. Of course, the basis for the payment is a valid inspection of the electrical installation, carried out in accordance with the law. 


You should also consider insuring your PV against theft or damage by vandals.


The cost of the policy with buildings insurance is about 30 PLN per year.

14. Plot for photovoltaics?

There are many factors that influence the choice of a site for a ground-mounted photovoltaic installation.


Different conditions must be met by the land on which the domestic installation will be built and different land for a photovoltaic farm.


The choice of the appropriate land is therefore an individual matter and depends on, among other things, the needs of the customer and the applicable regulations. Our consultants will be happy to help clarify this issue in detail.

15. Subsidies - money to install photovoltaic panels?

Currently, Poles can take advantage of many forms of assistance in the installation of photovoltaic installations.


For more information, see the “Subsidies” section.

16. How to use surplus energy produced by PV?

All photovoltaic installations must be connected to the electricity grid under current legislation. If you are installing PV panels on the roof of your house, you should submit a so-called micro-installation notification, and the utility must replace the meter with a two-way meter within 30 days. The next step is to annex your contract or sign a new one.


The new meter measures the amount of electricity you take from the grid and the electricity you give back to the grid. The only energy that will be given back is the energy that your panels produce and that you will not be able to use immediately.


Typically, panels produce surplus electricity from spring to autumn. You can take the electricity back to the grid at any time.

17. How does grid electricity storage work?

You only give back to the grid the surplus electricity produced by the photovoltaic installation that you have not been able to use. You can take back the stored electricity at any time, when you need it. You pay nothing for storing energy. As payment, the utility company will keep 20% of the stored energy.  For example, the installation produces 5000 kWh, you use half of it (2500 kWh), and give the rest to the grid (2500 kWh). The utility will take 500 kWh (20%* 2500 = 500). You will have 2000 kWh to collect.

18. Zero electricity bills - self-sufficiency?

Anyone with a photovoltaic installation must – by law – be connected to the electricity grid. You have no right to cut yourself off from it.


However, you can ensure that your photovoltaic installation produces as much electricity as you need. The balance of power should cover the whole year, because in summer the modules produce surplus energy, which you can use in winter when the panels are less efficient. For this reason, a connection to the power grid is essential, as this is where you can store any surplus electricity produced without incurring high costs.


Of course, you can also opt for an off-grid system, which will consist not only of photovoltaic panels, but also of capacious batteries and charge controllers. The off-grid system is useful in zero-energy houses and in buildings that are located in areas where the power grid often fails.


However, it should be remembered that the construction of an off-grid system is connected with the fulfilment of many conditions, as well as with considerable expenses on expensive batteries.

19. Increase in property value after installation of PV?

The value of the building increases significantly after PV is installed. Because the potential new owner can use it right away, which will reduce the cost of maintaining the house.


Answering the question “By how much does PV increase the value of the house?” is much more difficult. Because it is an individual matter and depends, among others, on the size of the installation, type and power of the modules, as well as how old the panels are and what their technical condition is.

20. What is the procedure for replacing a meter with a two-way meter?

Once you have installed a photovoltaic system in your home, you must send an application for connection of the microinstallation to the electricity provider to whom you belong. The electricity supplier has 30 days from the date of application to replace the meter with a two-way meter. This will measure how much electricity you take in and out of the grid.


You do not pay anything for the installation of a two-way meter.


You will probably be given a new customer number and bank account number to pay. The utility will also bill you for the electricity you used on the old meter.


Billing to the electricity company can be on a monthly, bi-monthly or six-monthly basis depending on what is stated in the comprehensive agreement with the energy supplier.

21. How and where can photovoltaic panels be installed?

Photovoltaic panels should be mounted on a suitably prepared rack. The mirror of the modules must be directed towards the south or possibly west, which are the sunniest directions. 


The rack for the installation can be placed on the roof of: a house, an outbuilding, a block of flats, a tenement house, a factory and many other buildings. It is important that the roof structure is strong enough to support the weight of the panels. Modules are also increasingly installed on a metal structure, placed directly on the ground.


It is also possible to mount photovoltaic panels instead of roofing a shed or terrace, on a balustrade, if the existing electrical installation in the building allows the use of such a device.

22. Photovoltaic guarantee - what is worth knowing?

All photovoltaic panels are covered by a manufacturer’s warranty. It is up to 25 years and concerns the linear decrease of power. The manufacturer guarantees to the customer that during this time the efficiency of the panels will not decrease by more than 20% (for installations up to 10 kW or 30% when the panels have more power).

23. How much energy is used annually in the house?

Electricity consumption in the home is an individual issue for each home. To accurately assess the annual electricity consumption of your home, it is best to look at your energy bills for the last 12 months.

24. Can the photovoltaic installation be used as a generator in case of emergency?

This is not possible because the panels also need electricity to operate and produce energy. 


To protect yourself in case of a grid failure, you can either buy a generator and prepare a place at the meter to connect it quickly, or choose an off-grid installation.

25. What is the size and weight of the panels?

This is usually approximately 1 metre wide and 1.67 cm long. Panels measuring 1 metre wide by 2 metres long are becoming more common. The weight of one panel is approximately 19 to 23 kg.

26. What is the lifetime of PV panels?

The manufacturer’s guarantee is 25 years, but good quality panels can produce energy for up to 50 years, provided of course that they are well installed and undamaged.

27. How quickly will the cost of a photovoltaic installation be recovered?

In most cases it is a maximum of 7 years, usually 5-6 years. In addition, if the customer receives a subsidy, this time will be shorter. You can also speed up the process if you make use of the thermomodernization allowance, thanks to which you can deduct PV expenses from your taxes for up to 6 years.

28. How much energy do photovoltaic panels produce?

The standard offer of Prowable sp. z o.o. includes photovoltaic panels of 390W. That is, each panel can optimally produce 390 kWh per year.

29. When to install PV?

The time of year does not matter, provided the roof is dry and the temperature is positive.

30. Monocrystalline or polycrystalline photovoltaic panels?

Both cells work well at the latitude where Poland is located. However, more and more often monocrystalline modules are installed, which are thin and have a dark colour (full black). They look particularly attractive on roofs covered with black or various shades of grey.

31. Inverter - what is it?

Inverter – A device that converts the direct current produced by PV panels into alternating current that can be used in the home.  It is an essential part of a photovoltaic installation.

32. Which inverter for a photovoltaic installation?

The choice is particularly dependent on the type of PV installation and individual customer needs. Prowable sp. z o.o. offers the assistance of an advisor who will tell you which model will best meet your expectations.


For smaller installations, a single-phase inverter is sufficient. In the case of a more powerful set, a three-phase inverter is necessary.


Microinverters are also available, which allow viewing and independent operation of individual photovoltaic panels. Microinverters are a good solution for people who plan to expand their photovoltaic installation in the future.

33. What is the angle of inclination of the panels?

The angle of inclination depends mainly on the angle of the roof and how the building is positioned. The panels are always installed on the southern slope of the roof where there is the most sunlight, then the eastern and western sides of the roof are taken into account.

34. PV installation on a company ?

A PV installation will work equally well on any building. However, when it comes to energy expenses, installing PV on a company building is very often the only way to significantly reduce business costs.

35. Can an entrepreneur include a PV system as a deductible expense?

This is how an entrepreneur is able to include a photovoltaic system as a deductible expense.

36. Is a photovoltaic permit needed?

If you own the building, land or plot of land, you do not need any permits.


It is different if you plan to install the system on a so-called common area, e.g. the roof of a tenement house or block of flats managed by a housing association.

37. What is net metering?

Net metering – means that the prosumer settles accounts with the power utility company for the electricity they have produced and fed back into the grid, as well as the energy they have taken from it.


For storing the surplus energy produced by the PV panels, the power company charges 20% of the electricity returned to it (in the case of installations up to 10 kW, or 30% if the PV has a larger capacity).  The customer pays only for the kWh he had to buy from the power grid.


From 2019, net metering can be used not only by individual customers but also by companies. However, such an installation must not exceed 50 kWp

38. Who is a prosumer?

A prosumer is both a producer and a consumer. The prosumer is a producer of electricity (surplus) which he gives back to the public grid. He is also a consumer, e.g. where he buys electricity produced by the electricity utility when needed.

39. I am self-employed, can I be a prosumer?

At the end of August 2019, new regulations came into force in Poland under which also small and medium-sized companies can be treated as prosumers. This means that entrepreneurs have the right to install photovoltaic installations and can store the surplus electricity they produce in the public grid. For storing the energy, the operator will deduct 20% from the surplus – in the case of installations up to 10 kW. When a prosumer has a PV installation with a larger capacity, storing the energy in the grid will cost them 30% of the surplus.

40. What is a kWp?

kWp – means the maximum power that can be achieved by photovoltaic panels when they are operated under so-called standard measurement conditions. In other words, how much electricity (1 kWh), a given panel or the entire photovoltaic installation is able to produce.

41. Does photovoltaics in Poland have low efficiency?

The key element is a well-designed and constructed PV installation that can power the house all year round. It is important to store the surplus energy you produce in the summer for use in the winter, when the performance of the PV installation drops due to weather conditions.

42. What conductors should be used in a photovoltaic installation?

Installers use different types of cables during installation – single-core, multi-core. They are selected accordingly to the photovoltaic set. In addition, they have several common features. Cables must be resistant to high and low temperatures, moisture, and they should be flexible and suitable for outdoor use.

43. What to look for when choosing photovoltaic panels?

When choosing, the most important thing is not the price, but the quality. The purchase of PV is not a small expense, and the installation should serve at least 25 years as offered by the manufacturer, and preferably even longer. Check who the manufacturer of panels is – is it a recognized Polish manufacturer such as Bruk-Bet Solar or Hanplast with warranty in Poland or a cheap, Chinese supplier such as JaSolar or EXE? Be sure of the warranty period for the panels, which should be at least 25 years.


In addition, a PV installation will not work without an inverter that converts direct current into alternating current. This current can be used in the home. When choosing an inverter, it is best to ask for help from one of our advisors so that it meets all your expectations. 


This also applies to installation. Our fitters have the necessary knowledge to install and connect the panels in the right way, without damaging the roofing, without short-circuiting and the installation will work efficiently for many years.

44. Can water be heated by a PV installation?

Photovoltaic panels are not used to heat water directly. PV modules are used to generate energy from the sun’s rays, which can then be used to power a boiler or water heater, for example.

45. When should I call for a photovoltaic service?

A service call should only be made if there is a prolonged, significant drop in power. Service technicians will then check the cause of the problem

46. Should photovoltaic panels be cleared of snow in winter?

PV panels should not be shoveled due to the risk of damage when shoveling snow. The panels are mounted at an angle to absorb as much sunlight as possible. In winter, snow does not settle too quickly on the panels, if it does it should melt quickly and run off during a thaw.

47. Should photovoltaic panels be washed?

The dirtier the panels, the less efficient they are, and therefore the less electricity they produce. Therefore we advise our customers to wash the panels at least every five years. If the panels are exposed to dirt faster, for example in the vicinity of a park, forest, pigeon house, then the panels should be washed more often.

48. How durable are PV panels?

PV panels are very durable. They are resistant both to high temperatures (up to +85 degrees Celsius) and low temperatures (down to -40 degrees Celsius). In addition, they can withstand large temperature fluctuations, e.g. during the day at +20°C and at night at 0°C. 


The PV installation is made of waterproof components. Even a thick snow cover should not damage the panels. Strong gusts of wind, even up to 130 km/h, should not pose a problem for a well-fixed installation. 


On the other hand, branches or broken trees may seriously damage the installation during a storm. The installation is also not resistant to large and strong hail or fire.

49. What is the cost of connecting the installation to the grid?

The customer does not pay any fees for connecting the installation to the public electricity network, these are paid for by the utility company. 


The utility company has a maximum of 30 days to install the meter after submitting the relevant grid connection application and replace the meter with a two-way meter. It does this at its own expense.

50. What is the impact of PV panels on the surrounding area ?

The panels do not affect the neighbourhood or its inhabitants in any way. It is a clean energy source that does not cause pollution. When generating energy, the installation works silently and does not cause vibrations.

51. Does photovoltaics produce CO2?

A PV installation is a clean energy source, generating electricity from the sun’s rays without producing any other environmental hazards.

52. Is a PV installation environmentally friendly?

A PV installation is 100% ecological as it produces clean energy from the sun’s rays without producing any other environmental hazards.

53. How long does it take to install a photovoltaic system?

The installation time depends on the size and angle of the roof, the type of roofing and the size of the PV system itself. The installation of the panels, cabling and inverter can take our team from one to several days.

54. What are the components of a photovoltaic installation?

The most important components of a photovoltaic installation are the panels, the inverter or microinverters, the cabling and the racking for mounting the modules.

55. What is the cost of a photovoltaic installation?

The cost of a PV installation is determined individually, as it depends on the order. The price is influenced by: the power of the installation, the number of panels, the type of inverter, the type of roofing, as well as the place of installation of the modules.

56. Selling surplus electricity?

Currently, prosumers cannot sell the electricity that the installation has produced. They can only store the surplus in the public electricity grid. They can use this energy at any time. However, it must be remembered that the time period for retrieving the surplus is 1 year.


For storing the electricity, the electricity grid will deduct 20% from the energy sent by the prosumer – if the installation has up to 10 kW of power – or 30% in the case of PV with a larger capacity.

57. Do photovoltaic panels work at night and on cloudy days?

The panels work when the sun’s rays fall on them, even when the sun is obscured by dense clouds. Then they work less efficiently due to the amount of rays that fall on them.

Photovoltaic panels do not work at night – due to a complete lack of sunlight.

58. What are the types of photovoltaic installations?

There are mainly two basic types of photovoltaic installations. These are the on-grid type:


on-grid – installed when the building is connected to the public grid. In the case of this type of installation, surpluses are returned to the public grid and can be collected at a later date by the installation user.


off-grid – used when the building is not connected to an external, public grid. The energy surplus is stored in batteries.

59. I have a question that is not on the list.

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