Solar Panels on a Private House: Roof and System Planning

The performance of solar panels depends on roof orientation, shading and how well the system fits the household's consumption. All of this is easier to plan before building or re-roofing.

In a climate with plenty of sunny days, turning a roof into a power plant seems a natural idea. Yet the same number of panels can give very different results on two houses. On one, the system covers a large share of daytime consumption; on the other, shading, the wrong angle or a set-up that does not match the household's needs leaves expectations unmet. A solar system is technical equipment, but it is also part of the roof and the house design.

Start by understanding consumption

Before choosing a number of panels, you need to know how much electricity the house uses and when. A year of electricity bills shows the seasonal pattern: air conditioners in summer, and electric heaters or a heat pump in winter, push the load up.

Timing matters as well. Panels produce energy during the day. If people are at home in daytime and the air conditioning, water pump or pool filter run during those hours, the output is used directly. If the family is out during the day and most consumption falls in the evening, exchange with the grid or battery storage becomes the key question.

The roof: orientation, pitch and shade

In the northern hemisphere, a south-facing pitched roof is considered the best surface for panels. East- and west-facing roofs can be used too: total output is somewhat lower, but it is spread more evenly across morning and evening. A pitched roof facing north is usually not a good choice.

Shade has a bigger effect than expected. Even a small shadow from a chimney, vent, satellite dish, neighbouring building or tall tree can pull down the output of a whole string of series-connected panels. To prevent this, panels are placed outside shaded zones, or equipment is chosen that manages each panel individually.

On flat roofs, panels are mounted at an angle on special frames. Row spacing must be calculated so that one row does not shade the next under low winter sun.

Structure and waterproofing

Panels, frames and the wind load acting on them add load to the roof structure. In a new house this is easy to account for in the design. On an existing roof, the condition of rafters, covering and fixing points should be checked by a specialist before installation.

Penetrating the roof covering to fix mounting brackets is a leak risk. Every penetration must be sealed with flashing elements suited to the type of covering. If the roof covering is due for replacement soon, it makes sense to do that before the panels go up; otherwise they will have to be removed and reinstalled.

Cable routes are planned in advance too: runs under the roof, along the facade or through a service shaft, the location of the inverter, and access for maintenance.

Types of system

• Grid-tied: surplus energy goes to the grid and shortfalls are drawn from it. With no battery it is simple, but for safety reasons it usually shuts down during a grid outage as well.
• Off-grid: for places without grid access. Battery capacity and a backup source are sized with cloudy days in mind.
• Hybrid: connected to the grid and fitted with batteries; it can cover evening consumption and short outages.

Grid connection rules, metering and permit requirements should be clarified in advance with the local electricity supplier.

Batteries deserve separate attention. Their capacity is sized to the household's evening and night-time consumption, but where they sit matters too: batteries must be protected from excessive heat and frost and kept in a ventilated place, separate from living rooms. A plant room that does not overheat in summer, or a shaded, protected enclosure, suits this purpose. The manufacturer's fire-safety requirements and installation clearances should be reflected in the design.

Planning checklist

• Collect a year of electricity consumption, month by month.
• Note the roof's orientation, pitch and any shading elements.
• Have the roof structure and covering inspected.
• Set aside a dry, ventilated and accessible place for the inverter and batteries.
• In dusty conditions, plan safe access for cleaning the panels.
• Get equipment warranty terms and a maintenance schedule in writing.

Zaferoğlu İnşaat also installs roof coverings in private house construction, and in its architectural designs the form and orientation of the roof are developed together with the overall plan of the house. Even if panels are not going on now, reserving a south-facing slope and a cable route in the design saves a lot of work later.