10 common mistakes when installing solar panels and how to avoid them

Last updated: October 17, 2026

Most solar panel installation mistakes don't become apparent on the first day; the system might work, but its output is less than expected, it might break down after a summer or two, or it might even become a hazard to the house. This article outlines 10 common design, installation, and usage errors, and explains how to avoid each one before you pay the price.

Design phase errors

1. Determining the size of the system by estimation

Many people request a "5-kilowatt system" simply because their neighbor has one, without considering their own consumption. The result is either a system too small to meet their needs, or a large system where some of the output is wasted, especially in split systems that don't export surplus.

How to avoid it: Start with a full year's bills or a list of actual loads and operating hours. A quick example: if your goal is to cover 900 kWh per month, the daily consumption is approximately 900 ÷ 30 = 30 kWh. With an approximate daily output of 5 kWh per kWh, you would need approximately 30 ÷ 5 = 6 kW of solar panels, before accounting for losses and site conditions. Try it. Solar system size calculator To obtain a preliminary estimate.

2. Ignore the partial shadow

The shade of a water tank, stairwell, or adjacent wall may cover a small portion of a single board, but it reduces the output of the entire string because the boards connected in series are affected by the weakest one. Shade also varies between winter and summer; what appears sunny in June may be shady in December when the sun is lower.

How to avoid it: Inspect the roof at different times of day, and consider the low winter sun. If there is no shaded area, raised structures may lift the panels above the level of obstructions.

3. Inappropriate direction and angle

Installing panels perfectly flat or at any angle that "suits the shape of the roof" is a common mistake. Flat panels accumulate more dust and are not easily cleaned by rain, and orienting them east or west can result in a loss of approximately 10 to 15% of production compared to orienting them south.

How to avoid it: Point the panels south, and adjust the angle of inclination close to the city's latitude: approximately 24° in Riyadh, 21° in Jeddah, 26° in Dammam and Qassim, 28° in Tabuk, and 18° in Abha. Details are available in the article. Best orientation and angle for panels in the cities of the Kingdom.

4. The inverter is not compatible with the panels.

Each inverter has a permissible voltage range at the panel input. If many panels are connected in series, the voltage may exceed this range, especially on cold winter mornings when the panel voltage rises, potentially damaging or shutting down the inverter. Conversely, if the series is too short, the inverter may not start working until late in the morning, and the voltage drops even further in the summer heat.

How to avoid it: The designer must calculate the number of panels in the string based on the panel and inverter specifications, as well as the minimum and maximum expected temperatures at your location. This is one of the skills you explain. MITS Free Academy At the basic technical level.

Installation errors

5. Weak or non-rust-resistant structure

The structure holds the panels for twenty years or more, exposed to sun, wind, sandstorms, and the humidity of the Jeddah and Dammam coasts, which accelerates rusting. Ungalvanized iron, thin sections, or poor roofing can cause the structure to warp or the panels to be ripped off in a strong storm.

How to avoid it: Choose structures made of hot-dip galvanized steel or aluminum, with sections calculated for panel area and height, and appropriate fixing for the surface type, whether concrete or metal. Estimate the appropriate structure from Solar Mounting Structure Calculator.

6. Cables with a smaller cross-section than necessary

Using a few meters of thick cable might seem tempting, but thin cables cause voltage drops, daily energy losses, and overheating of the connections, potentially leading to insulation melting. Furthermore, ordinary cables not specifically designed for solar energy crack under ultraviolet radiation over time.

How to avoid it: Calculate the cable cross-section based on current and distance, use dedicated solar cables and compatible connectors pressed with the correct tool, and secure the cables away from sharp edges.

7. Neglect of protection and grounding

Some installations only include panels and inverters, neglecting DC circuit breakers, fuses, lightning protection, and grounding. These components don't increase power output, so some omit them to reduce costs, but their absence exposes the system and the home to the risk of fire, electric shock, and damage in the event of a lightning strike or other malfunction.

How to avoid it: Make sure the price quote clearly states: DC circuit breakers and fuses, disconnect switch, transient voltage protection on both DC and AC sides, AC circuit breaker, and grounding of structures and devices.

8. Installing the inverter and batteries in a hot location

Placing the inverter in direct sunlight on a rooftop, or the batteries in a closed, unventilated room, raises their temperature, shortens their lifespan, and causes the inverter to automatically reduce its power output at midday. Similarly, attaching the panels to the roof without ventilation also raises their temperature; for every degree above 25°C, the power output decreases by approximately 0.29% to 0.40%.

How to avoid it: Install the inverter in a shaded and well-ventilated location, leave space under the panels for air to pass through, and keep the batteries in a place with a moderate temperature as much as possible.

Errors after installation and during operation

9. Over-discharging the batteries and choosing an unsuitable type.

Gel and lead-acid batteries are recommended to be discharged no more than approximately 50% of their capacity and have a lifespan of roughly 500 to 1500 cycles. Those who calculate the full capacity and use it every night will find the batteries depleted much sooner. Lithium phosphate batteries, on the other hand, can withstand a discharge depth of 80 to 90% and a greater number of cycles, approximately 3000 to 6000.

How to avoid it: Calculate the capacity based on the appropriate depth of discharge for the battery type, and do not add significant new loads to the separate system without reviewing the design. Ask the designer to explain the depth of discharge on which the calculation is based.

10. Neglecting cleaning and maintenance

In dusty areas, an uncleaned board can lose approximately 0.3 to 0.5% per day, meaning that two weeks without cleaning can result in a significant loss, and the loss is much greater after a dust storm. However, many systems are left without access routes or without monitoring of production data.

How to avoid it: Leave safe passages between rows of panels, clean them with water and a soft tool early in the morning rather than during the hot afternoon, and monitor production from the inverter app to detect any abnormal drop in output. Read Cleaning solar panels from dust وPeriodic maintenance checklist.

Additional error: Connecting to the network without formal procedures

Connecting a solar system haphazardly to the electricity grid can endanger network technicians and violates regulations. The regulatory framework for small-scale solar systems covers systems from 1 kilowatt to 2 megawatts for all subscriber categories. Implementation is carried out by a contractor qualified by the Electricity Regulatory Authority, and application and connection are handled by the Saudi Electricity Company. Always verify the current procedures with the relevant authorities before starting.

Quick review table before receiving the system

If you have an existing system and doubt its performance, or want to review a design before implementation, you can use a service Solar energy engineering consulting.

Frequently Asked Questions