Solar panel orientation: South or east–west?

Do all panels need to face south, or is an east–west layout worth considering? Before you choose, ask for two things to be compared: how much energy each option is estimated to produce, and when it will be available in relation to your own consumption.

The decision does not depend on the compass or the number of panels alone. The roof geometry, shading, equipment and your daily schedule all need to be taken into account. The aim of this guide is to help you know which alternative scenarios to ask for in the design study.

In the Northern Hemisphere, a south-facing orientation is often used when the priority is to maximize production. In an east–west layout, some panels face east and others west. SMA explains that the two sections reach peak power at different times, which can produce a smoother daily curve.

This does not mean that the second option will necessarily produce more kilowatt-hours or meet every morning and afternoon need you have. Ask to see the estimated production throughout the day. An appliance you use after sunset needs to be considered differently from consumption that coincides with production.

If one proposal includes more panels than the other, you are not comparing orientations alone. System size and equipment change at the same time, and the work involved may also differ.

First, ask for two scenarios with the same total panel capacity, as far as technically feasible. Then ask for a second comparison using the layout that can actually fit on your roof and is permitted. This lets you distinguish the effect of direction from the effect of system size.

For each scenario, keep a written record of panel capacity, inverter model, tilt, the orientation of each section and the assumptions used for losses. The European Commission’s PVGIS uses separate data for location, tilt, orientation, capacity and losses. A general estimate without these details does not adequately explain the difference between your proposals.

Ask for a roof plan showing the panel locations and the areas that must remain accessible: equipment, drainage outlets and maintenance paths. For a tiled roof, ask for the usable surfaces to be shown separately.

The Sunny Design documentation allows for different surfaces and orientations, maintenance paths and shading checks across different seasons. This is the kind of survey you can discuss in a meaningful way: not just a total panel count.

If you already have a solar water heater, also see our guide to combining it with solar panels on the same roof. The required checks of structural support and suitability remain the responsibility of the relevant professionals.

Describe when your main energy-consuming appliances operate on weekdays and weekends. For a business, also note operating hours, holidays and any seasonal closures. If you do not have detailed measurements, distinguish what you know from what is an estimate.

Ask the design study to show total production, the energy estimated to be used directly, and any surplus separately. A smoother curve is practically useful only if it serves loads that are present at those times.

A purely hypothetical example: scenario A produces 10.000 kWh annually and 3.500 kWh for direct use, while B produces 9.200 and 3.800 kWh respectively. The figures are arbitrary and intended to explain the comparison; they are not an estimate for an installation in Greece or an actual customer result. They show why you need both figures; by themselves, they do not prove which investment is worthwhile.

Do not base your choice on a single summer day. Ask for monthly results and daily curves for different seasons, using the same assumptions for both scenarios.

Also check how chimneys, parapets, trees and neighboring buildings have been taken into account. The JRC clarifies that the automatic horizon profile in PVGIS does not include very nearby obstacles, such as houses and trees. Therefore, an estimate from a map does not replace an assessment of the specific site.

To understand what each option offers, first ask for a comparison of the layouts, then for a storage scenario if you are interested. Ask which additional assumptions change and what equipment is included.

Do not treat east–west as an automatic substitute for a battery, or a battery as a reason to skip the roof assessment. To compare the final proposals, also use the solar panel quote comparison guide.

At Solar Home, we assess your site and the needs of your installation before deciding on the layout. Contact us to discuss which options are worth evaluating for your property.