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Planning a Solar System: 7 Steps to a Photovoltaic System

1.9.2022
  1. Is your house roof suitable for solar power?
  2. Step 1: Calculate the size of the photovoltaic system
  3. Step 2: Costs, subsidies and tax deductions
  4. Step 3: Do you need battery storage?
  5. Step 4: Do you need an e-charging station or wallbox?
  6. Step 5: Plan the photovoltaic system
  7. Step 6: Install the photovoltaic system
  8. Step 7: Apply for the subsidies
  9. Avoid these 5 planning mistakes

More and more homeowners want to produce cheap solar electricity and make themselves independent of electricity price fluctuations or supply bottlenecks with a photovoltaic system. In 2021, 43 percent more solar power systems were installed than in 2020. If you are also considering this, you should clarify whether your house and your household are suitable before planning a photovoltaic system.

Is your house roof suitable for solar power?

Solar radiation has a significant influence on solar power production and depends on two factors: Roof orientation and roof pitch:

  • The ideal roof orientation is to the south. However, a deviation to the south-east to south-west minimises the yield less than assumed for a long time. That is why photovoltaic systems on roofs with a south-east or south-west orientation make sense in many cases.
  • The ideal roof pitch is 30 to 35 degrees. The further the roof pitch deviates from these values, the more important the roof orientation becomes for electricity production. If the roof faces south, the yield should only drop by a few percent.

Houzy Advice

Good to know

In the article "Solar Energy: Is My Roof Suitable for a Solar System?" you can find out more about the ideal roof orientation and pitch and which other criteria are also important.

Houzy Hint

Tip

With our solar calculator you can find out how suitable the roof of your house is for a photovoltaic system. You can also calculate the solar power potential and simulate scenarios.

Step 1: Calculate the size of the photovoltaic system

The rule of thumb is simple: 1 kilowatt peak of power for 1000 kilowatt hours of annual electricity consumption. Kilowatt peak or kWp is the electrical power that solar modules generate under laboratory conditions. With 1 kWp, you produce about 900 kilowatt hours of electricity per year. An average single-family house consumes about 5000 kilowatt hours per year. 6 kWp would be sufficient for this. With 10 kWp you produce about 9000 kilowatt hours per year and are equipped for higher electricity consumption. For example, if you buy an electric car and install an e-charging station. For 1 kWp of power, you currently need about 7 square metres of solar modules, which means about 70 square metres for 10 KWP.

Houzy Advice

Good to know

The electricity bills of the last 12 months tell you how much electricity you consume. Calculate the size of the photovoltaic system with current data and a safety margin.

Houzy Hint

Tip

The result of the rule of thumb "1 kWp for 1000 kWh annual electricity consumption" is a first rough estimate of the required power. If you want to know more precisely, contact a solar professional.

Step 2: Costs, subsidies and tax deductions

A photovoltaic system with 10 kilowatt peak output costs about 25,000 Swiss francs. From the federal government you receive the performance-based small one-off payment (KLEIV), which amounts to up to 30 per cent of your investment costs, in our example about 4,000 Swiss francs. In addition, in every canton except Lucerne and Graubünden, you are allowed to deduct 100 percent of your net investment costs (investment costs minus one-off payment) from your taxable income if the system is subsequently installed. The bottom line is that our 10 kWp photovoltaic system for an average house with average electricity consumption costs around 20,000 Swiss francs, depending on income and tax progression.

Houzy Hint

Tip

In the article "Solar Power System: Is Solar Power Worthwhile?" find out more about costs and subsidies. With the solar calculator find out how much a photovoltaic system costs and how quickly it pays for itself.

Calculate the Solar Potential of the House Roof with the Solar Calculator

Solar potential and costs in a nutshell

With our solar calculator, you can analyse the solar potential of your roof in just a few minutes and calculate the profitability of a solar system.
Check Solar Potential Now

Step 3: Do you need battery storage?

Whether a photovoltaic system is worthwhile depends above all on your own consumption. You can increase your own consumption with a battery or electricity storage system. Self-produced solar electricity costs less than electricity from the grid. In Winterthur, for example, you pay 12 centimes more for a kilowatt hour of electricity than you receive for a kilowatt hour of solar electricity that you feed into the public grid. With an electricity or battery storage system, you get more out of your photovoltaic system: You ...

  • ... cover up to 80 percent of your consumption with climate-friendly and affordable solar power.
  • ... make yourself independent of your supplier, rising electricity prices and power cuts.
  • ... use more low-cost solar electricity and reduce your energy costs by around 30 percent.
  • ... amortise your photovoltaic system more quickly thanks to higher self-consumption.
  • ... increase the value of your home sustainably with a solar energy system and an electricity storage system.

Houzy Hint

Tip

Read in the article "Electricity Storage: Is a Storage Device for the Solar Power System Worthwhile?", what you should know about battery storage. With the solar calculator you can simulate self-consumption.

Step 4: Do you need an e-charging station or wallbox?

If you own or want to buy an electric car, an e-charging station is a must. Of course, you could charge the car at a household socket. But that is dangerous because cables or junctions in junction boxes can heat up and catch fire under full charging power. A wallbox is safer, faster and more convenient. An average single-family home consumes about 5000 kilowatt hours per year (see "Calculating the size of the photovoltaic system"), an average electric car about 15 kWh/100 kilometres. If you drive 15,000 kilometres a year, you need about 7250 kWh for the house and the car. A 10 kWp photovoltaic system is easily sufficient for this and still has sufficient reserves.

Houzy Advice

Good to know

Simple e-charging stations are available from 600 to 700 francs. For a better wallbox with 11 kilowatts of charging power, you should expect to pay 3500 francs for the wallbox, materials and installation.

Houzy Hint

Tip

Learn more about the topic of electromobility in the article "E-Charging Station or Wallbox: Smart Charging Solutions for Your E-Car".

Step 5: Plan the photovoltaic system

As soon as you have decided to install a photovoltaic system, you should commission a solar professional with the planning. He will clarify how high your energy consumption is, how it could change in the next few years due to an electric car, a sauna or a heat pump and how powerful the system would have to be. On this basis, the solar builder or installer calculates the economic efficiency and recommends solar modules, inverters and battery storage. Photovoltaic systems for single-family or two-family homes are usually planned by the installation companies. For larger projects such as apartment buildings, for example a condominium owners' association, there are special planning offices.

Houzy Hint

Tip

Solar professionals have their hands full. The climate crisis, the war in Ukraine and the rising energy and raw material prices have increased the high demand for solar power. That's why projects are taking longer than usual at the moment. Keep this in mind when planning your photovoltaic system.

E-Charging Station

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Step 6: Install the photovoltaic system

Leave the installation to a solar professional. Installing modules is easy if you don't suffer from vertigo, but connecting modules and inverters correctly and accurately requires experience. In our partner network you will find certified solar builders and solar installers who you can contact with just a few clicks. Ask them how many photovoltaic systems they have already installed and ask them for reference projects you can look at. Decide on an installation company from the region that offers you a quick on-site service if you should ever have any problems.

Houzy Hint

Tip

If you register the system with your building insurance company before installation, damage during installation is insured. Learn more in the article "Insure the Photovoltaic System Correctly".

Worker Installs Solar Panels on the Roof of a Single-Family House
As soon as you have commissioned the photovoltaic system, the solar installer can apply for the one-off payment on your behalf.

Step 7: Apply for the subsidies

The application for the one-off payment for photovoltaic systems with an output of less than 100 kilowatts may only be submitted after the system has been commissioned. The installer can apply for the one-off payment at www.pronovo.ch. Pronovo is responsible, among other things, for handling the federal government's renewable energy subsidy programmes. If you want to feed surplus solar power into the electricity grid, a connection application to the energy supplier is usually sufficient.

Avoid these 5 planning mistakes

Small mistakes can be costly. Therefore, when planning your photovoltaic system, avoid these 5 mistakes that others have already made:

  1. Old plans: Measure the available roof area precisely. Especially if you want to install a system on the roof of an older house. Old plans are often inaccurate or no longer up to date because, for example, skylights or hatches were subsequently installed.  
  2. Weight: Photovoltaic systems are heavy. Calculate 30 kilograms per square metre for a pitched roof and 200 kilograms per square metre for a flat roof plus the load of gusts, rain or snow. Without structural proof, a structural engineer or specialist planner must assess the load-bearing capacity.
  3. Distances: The higher the wind load, the greater the distance from the solar modules to the edge of the roof should be, otherwise the wind can tear modules out of their anchorage. Equally important is the distance between the modules and the roof. If they are calculated incorrectly, a dangerous suction effect or a fire-accelerating chimney effect can occur. That is why the planning and installation of photovoltaic systems is a task for solar builders and solar installers.
  4. Inverter: Photovoltaic systems produce direct current; your electrical and household appliances need alternating current. An inverter converts direct current into alternating current. If it is not optimally designed, the system will produce less than it could. You can have the design optimised by a solar installer or check and adjust it yourself with a programme.
  5. Shading: Consider the influence of shading on performance. Most people only pay attention to tall trees and neighbouring houses, but antennas, distant hills, chimneys or streetlights also cast shadows. You can leave out shaded areas when planning.

Do you want to produce cheap solar power, do something for the environment and make yourself independent of rising energy or raw material prices? A photovoltaic system is an investment in the future that pays off ecologically and economically. Use our solar calculator to find out whether your house roof is suitable, how much a photovoltaic system costs and how much subsidy money you will receive. However, you will probably need some patience: many solar professionals are currently very busy because the demand for photovoltaic systems is higher than ever before.

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