East-West vs South-Facing Solar: Yield and TOU

Last updated: November 2026

An east-west solar panel layout can spread output across the day or fit more capacity on a flat roof. A south-facing layout can produce more annual energy from the same capacity in the northern hemisphere. The better investment depends on which electricity the household uses, exports or stores, and what each interval is worth.

SurgePV publishes this post and sells solar design software.

This guide compares annual yield, household demand, roof geometry and electrical design. South-facing here means the northern-hemisphere comparison; in Australia and other southern-hemisphere locations, the equator-facing baseline is north.

The Yield Gap: How Much Energy You Actually Lose

The generation difference is site-specific, not a fixed east-west penalty. Tilt, weather, horizon and mounting assumptions all affect the result. Compare equal DC capacity first, then run a separate comparison for the maximum capacity that each layout can fit.

Annual Production by Orientation and Location

The following reproducible PVGIS calculations use crystalline-silicon modules, 14% entered system losses, free-standing mounting and the calculated terrain horizon. The south array is 6 kWp at 30° tilt; the split array is 3 kWp east plus 3 kWp west at 12°. These are modeled design examples, not measured installations or optimal-tilt recommendations.

Source: European Commission JRC PVGIS, API version 5.3, opened and calculated in November 2026. Responses identify PVGIS-SARAH3 solar data for 2005–2023 and ERA5 meteorology. For reproduction, use PVcalc with peakpower 6, angle 30, aspect 0 for south; then peakpower 3, angle 12 and aspect -90 or 90 for east and west. Set loss 14 and the coordinates shown above.

This comparison changes tilt as well as orientation because it represents two mounting choices. It cannot isolate the effect of azimuth alone. For an orientation-only experiment, hold tilt fixed and rerun all orientations. For a pitched roof, use its actual slope rather than borrowing the flat-roof assumptions.

The split results are the sum of independently modeled subarrays. They do not include a detailed shared-inverter clipping model, near-object shading, mutual row shading or an installation-specific snow model. Those omissions matter when converting a preliminary yield comparison into an equipment design.

What These Numbers Do Not Tell You

Annual energy alone cannot identify the cheapest annual electricity bill. It does not show whether generation coincides with demand, what exports earn, or whether a battery can absorb surplus. The PVGIS estimates above are a resource comparison, not a claim about household savings.

Use hourly or finer generation and consumption profiles for the economic comparison. Align their time zones and daylight-saving treatment before combining them. A one-hour shift can make an east or west array appear to match a tariff window that it actually misses.

Retain the weather dataset and modeling settings in the proposal. If a design revision changes modules, inverter capacity or roof planes, rerun both alternatives with the same assumptions. Otherwise, a favorable result may come from different loss settings rather than the orientation itself.

Self-Consumption: The Real Reason East-West Often Wins

Self-consumption is the fraction of generated solar used on site. It differs from self-sufficiency, which is the fraction of household demand supplied by solar. A smaller array may have a higher self-consumption percentage while supplying fewer useful kWh, so compare both percentages and energy totals.

Generation vs. Demand by Hour

East-facing output tends to arrive earlier than west-facing output, but the household must have demand during those intervals to benefit. West-facing modules cannot supply an evening peak after sunset. A sunny summer curve also cannot stand in for winter operation or an annual result.

For each interval without storage, direct solar use is the smaller of generation and demand. Export is generation remaining after direct use, subject to curtailment; grid import is demand remaining after direct use. Sum those quantities across the year rather than multiplying an assumed percentage by annual generation without checking the load.

Ask for interval meter data where available. If only monthly bills exist, document the assumed household schedule and show alternative occupancy scenarios. Working from home, electric water heating and daytime vehicle charging can change the preferred layout without changing roof geometry.

Self-Consumption Translates to Bill Savings

Here is a transparent arithmetic example using the Madrid PVGIS energy totals above. Assume annual household demand of 4,200 kWh, direct use of 2,700 kWh for south and 3,200 kWh for east-west, an import price of EUR 0.28/kWh and an export credit of EUR 0.06/kWh. These load overlaps and prices are selected assumptions, not measured results or a Spanish tariff offer.

Benefit equals direct use times the avoided import price plus export times the export credit. The assumed east-west case gains only EUR 14.57 a year despite using 500 more solar kWh directly. Installation cost, maintenance and tariff differences could easily change the decision.

The break-even condition is more useful than a universal price-ratio rule. If east-west loses 1,590.49 generated kWh and gains 500 directly used kWh, its benefit difference is 500 × (import price minus export price) minus 1,590.49 × export price. With the selected prices, the extra direct use just offsets the lost export value.

If the direct-use gain were smaller, south would win this example. If export were valued at the same flat price as imports, total credited generation would dominate, subject to settlement rules. This explains why a large import-to-export price ratio alone cannot guarantee an east-west advantage.

When South-Facing Still Wins

South-facing remains a useful northern-hemisphere baseline when it provides the most valuable usable generation at an acceptable installation cost. The following situations are reasons to model it carefully, not automatic selection rules.

1. Full-Retail Net Metering Markets

If an actual contract credits exports and imports equally across the relevant settlement period, timing may matter less than annual output. Check annual reconciliation, surplus treatment, non-bypassable charges and time-of-use periods before assuming every kWh has equal value. Do not infer the contract from a state name or a legacy tariff label.

A household that exports more energy than it imports may face different compensation for the annual surplus. That can weaken an otherwise simple argument for maximizing production. Use the settlement rules in the calculation rather than assigning one flat credit to unlimited exports.

2. Battery-Paired Systems With Adequate Storage

A battery can shift midday generation into later demand. This may make south-facing energy more useful, but there is no universal battery-capacity threshold at which south always wins. Usable capacity, charge power, round-trip losses, reserve settings and winter surplus all affect the result.

Compare incremental battery savings with the battery’s incremental cost. If both orientations already fill the battery on many days, extra midday production may still be exported. If neither fills it in winter, seasonal yield may matter more than the summer charging curve.

3. Pitched Roofs Already Oriented South

A suitable south-facing roof plane may offer straightforward installation and strong output. Its actual advantage depends on shade, structural capacity and usable area. A smaller unshaded east plane can sometimes be more valuable than a south plane obstructed by trees or equipment.

Include mounting complexity in the comparison. Reorienting modules against the roof pitch can introduce structural, wind and aesthetic constraints. A theoretical energy improvement should not be treated as free when it requires a different mounting system.

4. Off-Grid and Remote Sites

Off-grid systems must serve demand through low-generation periods. Annual kWh is only one part of that requirement. Evaluate seasonal resource, battery autonomy, generator backup and the timing of critical loads before choosing orientation.

A south-facing winter-focused layout can be a useful candidate in the northern hemisphere, while an east-west option may spread charging across the day. The preferred design should follow a reliability calculation rather than the import-export economics of a grid-connected home.

5. Commercial Loads With Midday Peak Demand

Daytime operating loads can use a south-facing production peak, but commercial schedules vary. Weekend closure, seasonal production and demand-charge measurement can change the value. Obtain interval data for the actual facility rather than borrowing a generic office or school profile.

Roof Geometry: What Your Roof Actually Allows

The roof must physically support the candidate layout before its energy result matters. Measure usable areas, roof planes, obstructions and required access routes before comparing orientations.

Pitched Roof Facing One Compass Direction

A pitched roof usually fixes the available azimuth and slope. A roof with a single east-facing usable plane is not a split east-west array. Treat each usable plane as its own subarray and record its module count and shade conditions.

If the existing south plane is small, using another orientation may increase total capacity without changing the first plane. The decision is then whether the additional modules are worthwhile, not whether the entire array should move away from south.

Pitched Roof With North-South Ridge

A north-south ridge commonly creates east and west slopes. Their usable areas need not be equal: chimneys, dormers, setbacks and access can make one side smaller. Start with the feasible panel counts before deciding whether an equal split is desirable.

Check that both slopes have suitable structural and weatherproofing details. The energy model should use the actual pitch of each slope. An assumed low-tilt flat-roof array cannot represent a steep pitched roof simply because both are called east-west.

Flat Roof

Flat roofs permit more freedom in orientation but still have structural, drainage and access constraints. Back-to-back east-west arrangements can reduce the wide row gaps associated with some south-facing layouts. The density improvement must be measured on a real layout rather than assigned as a universal percentage.

K2’s product brochure describes Dome 6 configurations using 10° or 15° elevation and south or east-west orientation. Those are product options, not a claim that every roof should use the same tilt. K2 mounting-system brochure, opened November 2026.

This comparison follows the mounting arrangements documented by K2 and the orientation considerations described in SMA east-west design guidance. It does not assign a roof-area-to-module-count conversion.

Inter-Row Spacing Math for South-Facing Flat Roofs

A simplified two-dimensional geometry check uses the module dimension along the slope, tilt and a selected solar elevation. Row pitch is the horizontal module projection plus the shadow gap. It is a preliminary geometry calculation; the actual design also needs solar azimuth, terrain, access and manufacturer requirements.

For illustration, choose a 1.13 m sloped dimension, 20° tilt and 9° solar elevation in the plane normal to the rows. The horizontal projection is about 1.06 m and the elevation is about 0.39 m. Dividing that elevation by tan(9°) gives about 2.44 m of shadow gap, so the row pitch is about 3.50 m.

These are selected geometric inputs, not a claim about Berlin at a particular clock time. Do not substitute the portrait or landscape module dimension without checking which edge lies along the slope. Also distinguish row pitch from the clear gap between rows; confusing them can materially reduce installed capacity.

For an east-west mounting system, use the manufacturer’s layout and structural method. Paired modules sharing a ridge still need allowances for system gaps, drainage and service access. A dense drawing that blocks maintenance routes is not an installable design.

TOU and Feed-In Tariff Economics

Time-of-use, or TOU, tariffs give electricity different values at different times. Export compensation can also vary by interval. Apply the actual tariff to each candidate generation profile before selecting an orientation.

Germany: Self-Consumption and Export Payments

For a German project, obtain the applicable export remuneration for the commissioning date, system capacity and operating arrangement. Keep that separate from the household’s import contract. A historical feed-in rate is not a general November 2026 rate, and neither rate determines the direct-use fraction.

Spain: Surplus Compensation

For a Spanish project, document the contracted import and surplus-compensation terms, including settlement limits. Do not assume a flat national export price. Shared self-consumption also requires a separate assessment of how energy is allocated among participants; aggregate generation alone cannot show each apartment’s bill savings.

UK: Smart Export Guarantee Offers

For a UK project, compare the actual export offer with the import plan and its eligibility requirements. A high export payment may change the value of self-consumption, especially if the customer changes import plans to obtain it. Keep equipment or supplier conditions visible in the comparison.

California: Net Billing and Legacy Arrangements

For a California project, determine whether the customer is on an existing net-metering arrangement or a net-billing tariff. Use the utility’s applicable schedule and export-credit file. A west-facing array can only benefit from a late-day payment while it is producing; a high post-sunset credit requires another energy source such as storage.

Australia: Use North as the Equator-Facing Baseline

In Australia, compare east-west with north-facing layouts rather than carrying over a south-facing recommendation. The relevant retail offer and network export conditions are address-specific. Use interval data to assess whether afternoon generation avoids peak imports or is simply exported under a different rate.

US Full Net Metering and Legacy Contracts

Where a contract treats imported and exported kWh equally, inspect the settlement period and annual surplus rules. Legacy status should be supported by the customer’s documents. Equipment expansion or account changes may require a fresh review with the utility.

Tariff-to-Orientation Quick Reference

Use generation and financial scenarios to document the comparison. Test a plausible tariff change as well as the initial offer, especially when the decision depends on a small annual difference.

The Battery Question

A battery can reduce the value of producing at the same time as household demand because it can move solar energy between intervals. It also introduces cost and losses. The result must be calculated for the specific battery and load profile.

Self-Consumption With and Without Battery

Keep a complete annual energy balance. Solar used directly plus solar sent to storage plus exports plus curtailment must reconcile with generation. Battery energy delivered to loads must account for losses and changes in stored energy. Household solar supply cannot exceed household demand.

In the earlier 4,200 kWh demand example, the south case already serves 2,700 kWh directly, leaving at most 1,500 kWh of annual imports to displace. The east-west case leaves 1,000 kWh. Those are upper limits before timing, charge power and seasonal constraints, not predictions that a battery will eliminate all imports.

Report both battery charging energy and delivered energy. Counting the energy sent into a battery as electricity already consumed by the household overstates useful output when losses are present. It can also hide a battery that fills frequently but has little later demand to serve.

Battery Economics in 2026

Use an actual installed quote rather than a continent-wide battery cost range. The incremental price should include compatible power electronics, switching equipment, protection, installation and any necessary electrical upgrade. Compare that incremental cost with incremental savings, not the combined savings from solar plus storage.

For an illustrative cycle, assume 1 kWh is diverted from export into storage and round-trip efficiency is 90%. At EUR 0.28/kWh avoided imports and EUR 0.06/kWh sacrificed export revenue, its energy benefit is 0.9 × 0.28 minus 0.06, or EUR 0.192 before degradation and other costs. These are example inputs, not battery specifications.

Ask about future storage during discovery, but keep an unpurchased battery as a separate scenario. A design that depends on a future battery should identify the required inverter compatibility, space and electrical provisions. Avoid claiming a future orientation benefit before the operating strategy has been modeled.

Inverter and Stringing Rules for Split Arrays

The inverter must support the actual string arrangement, voltage and current limits. Maximum power point tracking, or MPPT, controls the operating point of connected PV circuits; the number of physical sockets is not necessarily the number of independent trackers.

Rule 1: Distinguish Separate MPPTs From Parallel Strings

Separate trackers can allow east and west strings to operate independently. However, a single tracker is not automatically unsuitable for all split-orientation designs. SMA describes polystring operation, where differently oriented strings operate in parallel under specified conditions. SMA polystring requirements, opened November 2026.

SMA requires parallel strings to have the same series module count, technology and MPP voltage, and says modules within a series string must have the same orientation. This guidance must be applied with the selected inverter’s documentation. It is not permission to mix arbitrary modules or unequal strings.

Rule 2: Verify the Voltage and Current Windows

Check maximum open-circuit voltage under the applicable design temperature and the operating voltage range at relevant conditions. Also check each input’s current limits, the allowed number of parallel strings and any short-circuit-current requirement in the manual. A valid annual energy estimate cannot demonstrate electrical compatibility.

Use the selected module’s temperature coefficients and the inverter’s specifications. Check the standard and local design conditions with the responsible designer rather than choosing a temperature solely from a typical morning weather forecast.

Rule 3: Document String Length and Orientation

Label each string by roof plane, module count and tracker connection. Unequal module counts on independent trackers may be acceptable when each input remains within its operating range; combining them requires a different review. Do not substitute a percentage tolerance for manufacturer instructions.

SurgePV supports electrical workflows, but the responsible designer must verify the proposed topology against equipment documentation. No automatic mismatch detection or guaranteed loss reduction is claimed here.

Shading Behavior: Compare Both Roof Layouts

East-west has no universal shading advantage. An obstruction’s position, height and the sun path determine which modules lose light and when. Evaluate both candidate layouts with the same obstruction model.

A chimney can affect multiple roof planes at different times. Trees or nearby buildings near the eastern horizon can reduce early generation, while western obstructions can remove the late output that motivated a west-heavy layout. A single noon image will not capture either effect.

Use site shading analysis to examine the hours that matter to the tariff and demand profile. Distinguish the terrain horizon from near-object shading; the preliminary PVGIS examples above include a calculated terrain horizon but no roof-specific obstructions.

Module-level electronics can change electrical mismatch behaviour, but cannot recover sunlight blocked by an object. Their value depends on the layout, equipment and service arrangement. They should not be called mandatory for every asymmetrically shaded roof without a product-specific engineering reason.

When presenting alternatives, identify which assumptions could reverse the choice. If the east-west advantage relies on a tree being removed, show the result with the tree retained until removal is agreed and feasible.

Aesthetic and Permitting Considerations

The preferred energy layout still needs structural and local approval. Review the applicable requirements before promising a module count or final appearance.

Visual Symmetry and HOA Rules

Check local planning and homeowners-association conditions where applicable. Ask the project team to document any relevant solar-access protection rather than assuming an association can prohibit a design or that all restrictions are unenforceable. A concept drawing should identify any approval still outstanding.

Wind Loading on Flat-Roof East-West Mounts

Ballasted and attached systems distribute loads differently. The mounting supplier’s design method and the structural engineer’s assessment determine what is suitable for the roof, location and height. Do not choose attachment solely from a generic wind-speed threshold.

Check the applicable standard, roof condition, ballast load, sliding resistance and membrane compatibility. Setbacks and edge zones can reduce the usable area significantly. The final layout should reflect these constraints before the financial comparison is issued.

Snow Behavior

Low tilt can affect snow shedding, while snow load and drifting require structural review. No universal annual snow-loss percentage is applied here. Use the local climate and a documented modeling method, and explain any snow assumption that materially changes winter yield.

Maintenance access also matters after installation. A dense layout can be difficult to inspect or repair if the design leaves no practical route to equipment. Include serviceability in the comparison instead of treating every additional module as an unconditional benefit.

Decision Matrix: Which Layout for Which Project

Use this matrix to identify the next calculation or approval needed. It narrows the options without pretending that a tariff ratio, battery size or latitude can select the layout by itself.

Save the rejected alternative with a short explanation. This makes later revisions easier: if the customer changes tariff or decides against storage, the team can revisit the relevant assumption instead of starting from an undocumented rule of thumb.

A proposal should show annual production, direct use, exports, imports and installed cost side by side. Add the principal constraints and any unresolved approval. The customer should be able to see why a lower-yield layout was selected, or why additional yield justified a more expensive mounting arrangement.

Illustrative Layout Examples

The following are illustrative design examples, not documented customer installations. They show how to frame a decision without inventing measured project results.

Example 1: Berlin Townhouse, North-South Ridge

Assume a townhouse has usable east and west roof slopes and the occupants are away on weekdays. A south-facing alternative may not be physically available. Compare using both slopes with a west-only option, accounting for the different installed capacities and costs.

The Berlin PVGIS table is a low-tilt reference only; it is not a prediction for this pitched roof. Rerun the model at the measured pitch and include dormers, chimneys and nearby trees. If a future battery is considered, compare it separately from the initial installation.

The decision record should explain whether the extra east-facing modules produce useful morning energy or mostly low-value export. It should also show that every proposed string fits the selected inverter input. A roof that supports more modules does not automatically support the proposed electrical configuration.

Example 2: Phoenix Home With a South-Facing Roof

Assume a home has a usable south-facing plane and substantial daytime cooling demand. South is a credible starting candidate because generation may overlap demand. Obtain the actual utility tariff; no California-style legacy tariff is assumed for an Arizona property.

Compare the south option with other physically available planes. A north-south combination is not an east-west split and should be labeled accurately. Apply the cooling load profile across the year, because a high summer demand does not imply the same winter consumption.

If the available south roof meets the required capacity with straightforward mounting, an alternative direction may offer little value. If afternoon demand and tariff exposure are material, model a west-facing addition instead of assuming that all production should move west.

Example 3: Madrid Apartment Building Flat Roof

Assume an apartment building can accommodate either south-facing rows or back-to-back east-west pairs. Count modules after reserving access, drainage and structural exclusion areas. Then compare total production as well as production per installed kWp.

A denser east-west arrangement can potentially offset its lower per-kWp yield, but the amount depends on the actual layout. Use the Madrid resource comparison as a starting point, then add row shading and the chosen inverter configuration. Do not reuse a generic percentage uplift in module count.

For shared self-consumption, model participant allocation and settlement separately from aggregate building demand. More total generation is not necessarily more bill savings for every resident. Present the installation costs and allocation assumptions together so the building can assess both engineering feasibility and household value.

Conclusion: A Three-Question Answer

Start with three questions: which layouts are feasible, how much useful energy each produces, and what the installation and operating differences cost. Answer them with the same weather, load and tariff assumptions.

South-facing is a strong northern-hemisphere baseline; east-west can be valuable when usable roof area or production timing changes the economics. Storage, shade and settlement rules can reverse either result. Keep the assumptions visible rather than promising a universal direction or payback period.

Bring both feasible layouts to a SurgePV design demonstration to discuss roof modeling, energy-yield analysis and the proposal workflow. Engineering checks and equipment documentation remain part of the final design decision.

Frequently Asked Questions

Is an east west solar panel layout better than south-facing?

East-west can be better when roof capacity or generation timing improves the project economics. Compare feasible layouts using the actual load, tariff and installation cost; there is no universal winner.

How much energy does east-west lose compared to south-facing?

The yield difference depends on location, tilt, shading and equipment assumptions. The Madrid PVGIS example gives 9,662.80 kWh for south and 8,072.31 kWh for equal-capacity east-west, but those modeled inputs are not a universal penalty.

Why can east-west arrays fit more panels on a flat roof?

Back-to-back east-west mounting can use roof area differently from separated south-facing rows. The actual capacity gain depends on access, setbacks, structural limits and the selected mounting system.

Does an east-west solar layout match household consumption better?

It can match demand better when the household uses electricity during the additional morning or afternoon production. Use interval data, because west-facing modules cannot supply demand after sunset.

Should I choose south-facing if I have a battery?

A battery can improve the usefulness of midday south-facing generation, but it does not guarantee that south is best. Model usable capacity, power limits, losses and seasonal charging before selecting the layout.

What tilt angle works best for an east-west solar panel layout?

The best feasible tilt depends on the roof, mounting system and project objective. Compare actual product configurations and structural requirements rather than applying one angle to every roof.

Can east and west strings share an MPPT?

They can in manufacturer-approved polystring arrangements. SMA specifies matching series module counts, technology and MPP voltage for parallel strings, with a consistent orientation within each string; verify the selected inverter limits.