What Are Common Mistakes When Sizing Solar Systems for Winter?

Misunderstanding Solar Yield in Winter

When sizing solar systems for winter, many designers fall into the trap of simply reducing the summer yield by a fixed percentage. However, this approach overlooks the more significant impact of shorter days and reduced sunlight hours on solar power output. A more accurate method involves using a derating factor that takes into account the average winter irradiance and temperature. For example, a common derating factor for winter in the Northern Hemisphere is 20-30% lower than the summer yield, while in areas with mild winters, a 10-20% reduction may be more suitable.

Overlooking Temperature Effects on Efficiency

Temperature has a significant impact on the efficiency of solar panels, with efficiency decreasing by around 0.5% for every degree Celsius above 25°C. In winter, temperatures are often lower, but this can still affect panel efficiency, particularly if the system is not designed to account for these effects. To accurately size a solar system for winter, designers should consider the average temperature range for their location and adjust the system size accordingly.

Importance of Accurate System Sizing

Accurate system sizing is critical to ensuring that the solar system meets the energy needs of the building during the winter months. Overestimating winter yields can result in an oversized system, which not only increases upfront costs but also reduces the payback period and return on investment. Conversely, undersizing the system can lead to energy shortfalls and the need for costly backup power systems. By using a derating factor and accounting for temperature effects, designers can create accurate and reliable solar systems that meet the energy demands of their users year-round.