South-Facing vs East-West Solar Panels: Which Layout Wins?

“South is best” is the one solar rule of thumb almost everyone has heard, and in the Northern Hemisphere it isn’t wrong — a south-facing array does capture the most total energy over a year. The trouble is that this single true statement gets stretched into two false ones. The first is that an east-west roof is a poor candidate for solar, which sends homeowners into unnecessary despair or into paying for roof modifications they don’t need. The second is that orientation is the decisive variable, when in practice it’s usually not even in the top three. If an installer has told you your east-west roof “isn’t really good for solar,” or has waved orientation away entirely as though it never matters, both claims deserve a harder look, because the honest answer sits between them and depends on numbers specific to your house.

How the two layouts really compare, in kilowatt-hours and in dollars

Start with the size of the penalty, because most people badly overestimate it. A south-facing array at a sensible tilt points most directly at the sun’s arc across the day, so it sets the benchmark — call it 100%. Panels facing due east or due west each produce less over a full year, but the drop is smaller and gentler than the folklore implies. Treat the following as typical modeling results for a mid-latitude US roof at common pitches, not as guarantees for your specific address, because latitude, roof angle, and local climate all shift them. A due-south array is the 100% reference. Southeast or southwest facing lands around 95 to 98% of that. Due east or due west comes in somewhere around 80 to 88%. An east-west split, with roughly half the panels on each slope, produces about that same 80 to 88% combined, since each half is simply an east or a west array. North-facing panels manage maybe 60 to 70% and are rarely worth building in the first place.

Two things in that range are worth sitting with. The first is that southeast and southwest are nearly free. A roof that’s thirty or forty-five degrees off due south — which describes an enormous share of American houses — gives up only a few percentage points, not enough to change any real decision. If your roof faces “kind of south,” you effectively have a south roof for planning purposes. The second is that even a full east-west split typically lands within twelve to twenty percent of the south benchmark. That’s a real cost and worth accounting for, but it belongs in the category of “size the system a little larger,” not the category of “your roof doesn’t work.” A homeowner who hears “you’ll lose fifteen percent” and pictures a system that barely functions has the scale of the problem wrong by an order of magnitude.

What genuinely can sink a roof is shade, and shade routinely matters more than orientation. A south-facing roof under a mature tree or in a chimney’s afternoon shadow can easily produce less than a completely clear east-west roof, because shade doesn’t shave a few percent — a shadow crossing the wrong panels at the wrong time of day can knock out far more than orientation ever would. This is why the sequence of questions matters. Before anyone debates south versus east-west, the real screening question is whether the roof gets clean, unobstructed sun through the productive middle of the day, and how the various suitability factors interact is its own subject worth understanding in the broader roof suitability discussion. Orientation is a fine-tuning knob. Shade is a pass-fail gate. A good proposal reflects that by showing a modeled production estimate built from your actual roof — its planes, pitches, and shading — rather than reciting a rule of thumb and moving on. If a quote leans on “south is best” as an argument without ever modeling your particular geometry, it’s skipping the work that would tell you whether the rule even applies to you.

Total production is only half the comparison, though, and the half sales conversations tend to skip is the part that can flip the whole thing: south-facing and east-west arrays don’t just differ in how much they produce, they differ in when. A south-facing array produces a tall, narrow peak centered on midday, generating hard when the sun is high and tapering off sharply on either side. An east-west split produces a flatter, wider curve. The east-facing half wakes up early and does its best work through the morning, then fades. The west-facing half is sluggish in the morning and hits its stride in the afternoon and into the early evening. The daily totals can be similar, but the shape of the two curves is completely different, and the shape is where the money increasingly lives.

Whether that flatter shape helps or hurts depends entirely on how your utility pays you for the electricity your panels make, and that has been changing across the country. Under old-fashioned full retail net metering, the grid credits every exported kilowatt-hour at the same rate you pay to buy one, so timing is irrelevant — a kWh sent to the grid at noon is worth exactly as much as a kWh you use at 7 p.m. In that world, you should chase total production and south wins cleanly, no asterisk. But that arrangement is fading. Under time-of-use rates or reduced export credits, a kilowatt-hour you use at five in the evening — when you’re home, cooking, running the air conditioning against the day’s accumulated heat — is worth far more than a kWh you export at noon for a fraction of retail. A west-leaning or east-west array produces more of its energy during those valuable late-day hours, which means it can deliver more actual dollar value per panel than a south array that dumps its peak onto the grid at the exact moment that grid pays the least.

California is the clearest example of this shift in practice. After the state overhauled how exported solar is compensated, the timing of production started mattering much more than the raw annual total, and a west-facing array that leans into the expensive evening hours can pencil out better than a south-facing one that produced more kilowatt-hours but earned less for each of them. The specifics of how that plays out in a market that has moved away from retail net metering are worth reading about in the context of California’s post-net-metering landscape, but the general lesson travels well beyond one state. As more utilities push toward time-of-use pricing and lower export rates, the value of a panel is drifting away from “how many kilowatt-hours does it make” and toward “how many does it make when they’re worth the most.” An installer who models only annual kilowatt-hours on a utility that has stopped paying retail for exports is quietly optimizing the wrong number, and the homeowner is the one who pays for the mismatch.

The east-west roof’s quiet advantages, and running your own numbers

An east-west gable often comes with two advantages that a single south face can’t match, and they’re easy to overlook when you’re fixated on the orientation penalty. The first is usable area. An east-west roof gives you two workable planes instead of one, which frequently means room for a larger system. Roof area constrains system size more often than homeowners expect, and how roof geometry limits what you can install is a real ceiling for plenty of houses. A twenty-percent-larger array running at eighty-five percent per-panel efficiency will comfortably out-produce a smaller “optimal” south layout, so the extra planes can more than repay the per-panel penalty. The second advantage is a longer solar day for self-consumption. Because the east half covers your morning routine and the west half covers your evening, an east-west system generates during more of the hours you’re actually drawing power — the coffee maker at seven, the dishwasher and air conditioning at six. That raises the share of your own solar you consume directly instead of exporting, and under weak export rates the kilowatt-hours you use yourself are the most valuable ones you produce.

None of that comes free, and the honest downsides deserve naming. You may need a few extra panels to hit a given annual production target, which is real added cost even if the per-watt price of those incremental panels tends to be favorable. And splitting an array across two orientations has consequences for the electronics: panels facing different directions produce different amounts at different times, so they shouldn’t share a single conventional series string, where the weakest panel drags the rest down. Expect the design to use microinverters, power optimizers, or a string inverter with separate inputs for each roof plane. That’s a normal, well-understood engineering choice rather than a red flag, but it’s worth confirming the proposal accounts for it, because a design that wires two orientations into one plain string is leaving production on the table.

It’s worth putting rough numbers on how these advantages and costs net out, because the abstract version misleads in both directions. Picture a household on a time-of-use rate whose south-facing option would produce, say, 9,000 kWh a year, versus an east-west option on a roomier set of planes producing 8,600 kWh. On paper the south array wins by 400 kWh. But suppose the south array exports 60 percent of its output at a reduced midday export rate, while the east-west array — generating more in the morning and evening when the household is actually home — self-consumes a larger share at full retail value. Once you weight each kilowatt-hour by what it’s actually worth rather than counting them all equally, the east-west array can come out ahead in dollars despite the lower raw total. None of those specific figures will be yours, and the balance tips the other way entirely under full retail net metering, where every exported kilowatt-hour is worth the same as a consumed one and the raw total is all that matters. The point isn’t that east-west always wins; it’s that “which produces more kilowatt-hours” and “which saves more money” are genuinely different questions once export rates diverge from retail, and only the second one pays your bill.

The decision, in the end, rarely reduces to orientation alone, so the sensible process is to run your own numbers rather than accept a talking point. Start by pulling your last twelve months of usage in kilowatt-hours from your utility account, so you know the target you’re sizing toward. Then model production for the roof planes you genuinely have — the solar panel calculator lets you compare orientations and see how much output an east-west layout gives up at your usage level, which turns the abstract “you’ll lose some production” into an actual number you can weigh. Next, check how your utility compensates exports: under full retail net metering, chase total kilowatt-hours and favor south; under anything weaker, give the afternoon-heavy layout extra credit for producing when energy is worth more. Finally, compare competing proposals on their estimated annual production and their estimated first-year bill savings, not on orientation slogans, because those two numbers already fold orientation, shade, and rate structure into a figure you can act on. A south roof is a pleasant head start and nothing more. Plenty of east-west homes run this exact process and come out fine — and under the rate structures spreading across the country, a growing number come out ahead.

The one place not to compromise, whichever orientation you land on, is the shade check, because it’s the factor that can quietly undo a good orientation. Before you fixate on the few percentage points between south and east-west, make sure whichever planes you’re using stay clear of shadow through the productive middle of the day across the seasons, since a tree that’s bare in winter fills in by summer and an afternoon chimney shadow that misses the array in June can clip it in the shoulder months. An installer’s shade assessment should account for that seasonal movement rather than a single snapshot. Get the shade question settled first, treat orientation as the fine adjustment it is, and the south-versus-east-west decision shrinks back to the modest, manageable trade-off it actually is.