Why Solar Panels Shouldn’t Always Face South

Solar panels depend on light from the sky to make electricity. Therefore, facing them the right direction will allow your panels to produce the most power at the most important times. Read on or watch the video to find out why South is often, but not always, the best direction for solar panels in Ireland.

Why South is Not Always the Best Orientation for Solar Panels

Why Face Solar Panels South?

Photovoltaic solar panels produce electricity from light. More light means more electricity. You might have heard that a South-facing garden gets more light than a North-facing garden. Well, it’s the same for solar panels. Researchers have found that in Ireland, South-facing panels produce the most electricity. So why is South not always the best direction for solar panels?

Sun and Clouds in the Southern Half of the Sky
In Ireland, the Southern sky is generally brighter than the Northern sky

Why Face Solar Panels East-West?

East-facing panels produce most power in the morning. On the other hand, West-facing panels produce most power in the evening. By combining East-facing and West-facing panels in one system, you get high power output from early morning right through to late evening. This is ideal for people who work away from home during the day. These people generally need less power during the day while they’re away at work and more power during the morning and evening while they’re at home. East-West arrays are ideal for meeting this pattern of electricity demand. For a similar reason, East-West arrays are very popular with Irish dairy farmers who go solar. This is because power-hungry milking equipment is mostly used in the morning and in the evening.

West-facing solar panels on the roof of a house in Ireland catch the evening sun
These West-facing solar panels provide high power output late into the evening. Image credit: Energyd.ie; License CC:BY.

But What About the Reduced Power Output?

True, South-facing solar panels still produce about 16% more power than East-West panel systems. However, boosting the power of East-West solar panels to match South-facing solar panels can cost very little. The benefit of a better generation profile is often well worth this small added cost. On top of this, you can increase “DC over-sizing” with East-West solar panels compared to South-facing solar panels. “DC over-sizing” means using more than 3kW of solar panels with a 3kW inverter. You can do this with an East-West system because the panels will never all be at maximum output at any one time. This way, DC over-sizing helps you get the maximum return for your investment by controlling inverter costs.

Other Directions for Solar Panels

Solar panels in Ireland will produce some electricity no matter what direction they face. However, North-facing solar panels produce substantially less power than South-facing solar panels. North-East and North-West are also fairly poor choices of orientation. On the other hand, South-West and South-East facing solar panels will produce almost as much power as South-facing panels.

Solar Panel Slope/Tilt/Angle

Another consideration is how much to tilt your solar panels. It’s often said that the angle of your solar panels should match your latitude. However, this does not take account of scattered light. In reality, a tilt of around 30 degrees from horizontal is about ideal in Ireland. Luckily, 30 degrees is roughly the slope of a pitched roof, and getting the angle exactly right is not critical. It’s also worth noting that steep angles are best in winter while shallow angles are best in the summer.

Conclusion

South-facing and East-West facing solar panels both have their merits. Choosing the right direction for you will depend on the way you use electricity. In particular, you should consider what time of day your electricity demand is highest. Practical considerations, like the layout of your roof, may also affect your choice of orientation.

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