You should carefully consider which way to face your solar panels. Solar panels depend on light from the sky to make electricity, and facing them in the right direction will allow your panels to produce the most power at the most important times. Read on to find out why South is often, but not always, the best direction.
Solar PV panels produce electricity from light. The more light that reaches them, the more electricity the panels will produce. 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?
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 can 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 much 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. This is because power-hungry milking equipment is mostly used in the morning and the evening.
But what about the reduced power output?
True, panel-for-panel, South-facing PV systems still produce about 16% more power than East-West PV systems. However, boosting the power of an East-West to match a South-facing array 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 an East-West system compared to a South-facing system. “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. DC over-sizing helps you get the maximum return for your investment by controlling inverter costs.
South-facing and East-West facing solar PV arrays both have their merits. Choosing the right one will depend on the way you use electricity, especially what times of the day your demand is highest. Logistical considerations, like the layout of your roof, may also play a role in your decision. A site survey will help you to weight up all of these factors and come to the best decision.