South-facing vs east-west solar arrays — why the lower-yield option often wins for business

Ask most installers about panel orientation and you'll hear "south-facing is best." For maximising total kilowatt-hours, that's true. But it answers the wrong question for a business. Your goal isn't to generate the most electricity — it's to generate the most electricity you actually use on site, because that's what's worth your full retail rate rather than the much lower export rate. Once you frame it that way, an east-west layout often wins.

This guide is about which way the panels face. Where the array physically sits — roof, ground, or carport — is a separate decision covered in ground-mount vs roof-mount. The orientation logic below applies whichever you choose, though it bites hardest on flat commercial roofs where you genuinely have a free choice.

What each orientation does

South-facing points all the panels at the midday sun. It produces the highest total annual yield — around 950 kWh per kWp in southern England — concentrated in a tall spike around the middle of the day.

East-west splits the array: half the panels face east, half face west, usually on an A-frame across a flat roof. Total annual yield drops by roughly 15% versus south. But instead of one midday spike, you get a flatter, wider curve — generation ramps up in the morning from the east-facing panels and stays up into the late afternoon from the west-facing ones.

Why the flatter curve is worth more to a business

Picture a typical commercial load: people arrive, equipment switches on, and consumption runs steadily across the working day, often with a morning ramp-up and an afternoon that doesn't fall away until closing.

A south-facing array dumps most of its output in a few midday hours. If that exceeds what you're using at that moment, the surplus is exported — earning you the low SEG rate instead of offsetting your ~28p retail rate. You've generated lots of electricity but captured less of its value.

An east-west array spreads its output to match that working-day shape. More of every kilowatt-hour is consumed on site, at full retail value, across more hours. So even though it generates ~15% fewer total units, it can deliver more financial benefit.

The comparison, in pounds

Talking about curves is fine; the argument only lands when you price it. Take a 100 kWp array on a flat roof in southern England, importing at 28p/kWh and exporting at 6p/kWh (deliberately conservative — see the note on export rates below).

South-facing, 100 kWp

• Annual generation: 95,000 kWh
• Self-consumed at ~55% (the midday spike overshoots the load): 52,250 kWh × 28p = £14,630
• Exported: 42,750 kWh × 6p = £2,565
• Total annual benefit: £17,195

East-west, 100 kWp

• Annual generation: 80,750 kWh (~15% less)
• Self-consumed at ~72% (the flatter curve tracks the working day): 58,140 kWh × 28p = £16,279
• Exported: 22,610 kWh × 6p = £1,357
• Total annual benefit: £17,636

East-west generates 14,250 fewer units and still returns ~£440 more a year — because it puts a far larger share of them through the meter at 28p instead of out to the grid at 6p. Same capex, same roof, better return, from a layout the total-kWh column says is worse.

The bigger lever: east-west fits more panels

The pounds comparison above holds capacity constant, which understates the case. On a flat roof the two layouts don't fit the same amount of kit.

South-facing rows must be spaced widely so they don't shade each other, and they sit at a steeper tilt that catches more wind — meaning more ballast. East-west A-frames nest back-to-back at a shallow tilt, so they pack in roughly 30–50% more kWp on the same roof, with less wind load and less ballast.

Run the same roof again, fitting 130 kWp east-west instead of 100 kWp south:

• Annual generation: ~105,000 kWh
• Self-consumed at ~62% (a bigger array overshoots the load more often, so the rate falls): 65,100 kWh × 28p = £18,228
• Exported: 39,900 kWh × 6p = £2,394
• Total annual benefit: ~£20,620

That's ~£3,400 a year more than the south-facing option on the identical roof. It costs more too — at ~£900/kWp, the extra 30 kWp is roughly £27,000 — so the incremental capex pays back in about eight years, broadly in line with the base system rather than dramatically better. The honest read: east-west on a flat roof doesn't just return more per pound, it lets you build a materially larger asset on the same footprint at a similar payback. Whether you want that bigger asset is a capital-allocation question, not a solar one.

A note on export rates

The worked figures above use a deliberately conservative 6p export rate. Real 2026 business SEG rates run considerably higher — roughly 8.5p to 15p/kWh depending on supplier. That matters here, because a better export rate narrows the gap: the more your exported units are worth, the less the south-facing spike costs you.

At 15p export, rerun the 100 kWp comparison and south-facing pulls slightly ahead. So the east-west case is strongest when your export rate is poor and your import rate is high — which is the common position, but check yours before treating it as settled. If you're on a genuinely good export tariff, the orientation question gets closer and the decision may swing on the roof-packing advantage instead.

When south still wins

East-west isn't always the answer:

• Limited roof area. If you can only fit a small array, you want maximum yield per panel — go south.
• A genuinely midday-peaking load. Some operations really do peak in the middle of the day; south matches them.
• A strong export tariff. As above — good SEG rates reduce the penalty for exporting the midday surplus.
• You're adding a battery. A battery can soak up the south-facing midday spike and release it later, which neutralises south's main downside. (See battery storage for commercial solar.)
• Pitched roofs that already face a particular way — you work with the roof you have.

The decision rule

Don't choose orientation on total-yield bragging rights. Match the generation curve to your consumption curve. The way to do that properly is to ask your installer to model self-consumption and financial return for both layouts against your half-hourly consumption data — not just the headline annual kWh. A good installer can do this; if they only quote total generation, push them, because total generation is the number that flatters south while hiding the value question. Our half-hourly data guide explains how to get that data before you commission any modelling.

Sanity-check

1. What does my load shape look like across the day? Spread across working hours → east-west likely better. Sharp midday peak → south.
2. Is the installer comparing self-consumption and £, or just total kWh? Insist on the former, for both layouts.
3. Flat roof? East-west usually fits 30–50% more capacity with less ballast and lower wind load — get both priced, not just the one they defaulted to.
4. What's my actual export rate? At 6p the east-west case is strong; at 15p it narrows considerably.
5. Battery planned? If yes, south's midday spike becomes far less of a drawback.

The bottom line

South-facing maximises electricity; east-west often maximises value for a business by matching the working day and capturing more generation at the retail rate. On the same 100 kWp it can return a few hundred pounds a year more despite generating 15% less — and on a flat roof, where it packs in 30–50% more capacity, it can return several thousand more. The lower-yield layout is frequently the higher-return one. Make the installer model self-consumption and pounds for both against your real usage — that comparison, not the total-kWh figure, is the one that decides your return.

To see the savings case for your building, run the calculator. For where the array should sit in the first place, see ground-mount vs roof-mount. For how storage changes the orientation calculus, see battery storage. For payback fundamentals, read commercial solar payback in 2026.

General information. Self-consumption rates are illustrative and site-specific — have your installer model both layouts against your half-hourly data before deciding.