If you are planning a PV system with battery storage, careful preparation lays the foundation for an economically successful project. Generating your own electricity increases your independence and protects you against the erosion of purchasing power. It becomes especially attractive when your own contribution keeps the cost of a complete PV system low from the outset.
👉 It usually starts with the roof:
The number of solar panels that fit on the roof determines the output of the PV generator—in other words, the peak capacity in kWp that can be installed. This then determines the size of the inverter or hybrid inverter and, naturally, the photovoltaic system with battery storage as a whole.
💻 Step 1: Simple planning and digital measurement
Today, the easiest way to get started is with free design software such as K2 Base. The program does much of the work for you: simply enter the address, mark the building on the map and select the roof-tile type. Approximate dimensions are available immediately. You then only need to add details such as rafter spacing and the heights of the eaves and ridge.
👉 Get free access to K2 here.
📏 Step 2: Measure the roof yourself as an alternative or cross-check
If you prefer a conventional approach or want to verify the digital dimensions, you can measure the roof yourself in a practical way. The width can often be measured from outside with a folding ruler or tape measure.
There is a simple trick for determining the height: measure the height of a single roof tile—for example from a roof window—and count the tiles from the eaves to the ridge. This provides a very reliable measurement for optimising the solar-panel layout on the roof.
If the roof does not provide quite enough space, panels can also be installed on the façade or on a ground-mounted structure.
☀️🔋 Step 3: Tip—make full use of the roof
People often ask whether it is better to leave a margin or cover only part of the roof. Our recommendation is to fill the available area in one operation wherever possible. Solar panels are currently extremely affordable and can easily last more than 30 years. Adding panels later is usually disproportionately expensive and more complicated.
A few practical placement tips:
- Remove obstacles: relocate satellite dishes where possible. This creates valuable room for additional panels and produces a cleaner appearance.
- Distance from the gutter: do not install too close to the gutter. During heavy rainfall, water could otherwise shoot over it.
- Distance from the ridge: it is generally wiser to stop slightly below the ridge because ridge tiles are often firmly mortared in place and difficult to remove.
- Pay attention to wind loads at the roof edges: wind pressure is particularly high around the edges because turbulence forms there. Depending on the structural design, it may sometimes be possible to omit a rafter hook in the centre of a panel array. At the edges—especially when installing right up to the sides of the roof—use sufficient, secure fixings. K2 software provides precise results for this.
🧩 Step 4: Choosing panels—bigger is not always better
The first instinct is often to choose enormous panels with the highest wattage. Be careful, however: they are extremely awkward to handle. Slightly smaller panels can be arranged much more flexibly on a roof, almost like pieces of a puzzle. As a result, a greater total capacity may fit into the available area.
There is also an aesthetic consideration. Complete full-black panels—with a black frame and black backsheet—look exceptionally elegant. However, completely black surfaces heat up more strongly in sunlight, and heat slightly reduces output. In midsummer, the yield can therefore be around 5% lower.
📋 Step 5: Efficient installation and automatic bills of materials
Portrait versus landscape orientation
On conventional detached houses, the roof timbers or rafters run from the top downwards. The mounting rails must be fixed across them.
If the panels are installed in portrait orientation, each panel requires only around one metre of rail and substructure. Landscape installation requires almost two metres. Portrait orientation can therefore reduce material costs considerably.
👉 The result
The planning software automatically produces a structural calculation, installation plan and precise bill of materials. This allows you to determine the total system capacity and number of panels, design the strings and compare different panel types.
👷 Step 6: Who will install the panels on the roof?
If you do not want to carry out the roof work yourself, it is generally best to appoint a roofing contractor. Roofers usually move across the roof much more quickly and safely than electricians and often have appointments available sooner.
➡️ Conclusion and outlook
The foundations are now in place: plan the roof layout, choose the panels intelligently and obtain prices for the mounting materials.
In the next two articles, we will cover essential principles that help prevent planning errors and enable you to understand, install and operate the system correctly:
Important photovoltaic principles—Part 1
- Understand the important standard test conditions.
- Plan current and voltage correctly.
- Understand the influence of temperature.
Important photovoltaic principles—Part 2
- Understand data sheets.
- Connect panels correctly—in series or in parallel.
☀️ Keep sunshine in your heart—until next time!
Alexander & Dat
inutec