Albedo Values for Solar Design: Table by Surface

Last updated: November 2026

Albedo is one input that looks minor until you model a bifacial system. A wrong ground value shifts the rear-side light, and with it the yield estimate. This guide gives PVsyst’s reference coefficients by surface, the ground-reflection formula with a worked example, and how to measure albedo on site. Roof color is only a rough guide to reflectance.

Albedo values by surface material

The values below come from PVsyst’s usual albedo coefficients, read on 28 October 2026. Sandia’s PV Performance Modeling Collaborative lists the same values. PVsyst says the value usually used in urban localities is 0.14 to 0.22. It says the value can go up to 0.8 for snow cover.

The table has no row for soil, sand, gravel, white roof membranes or green roofs. For those, ask the supplier for the product’s measured solar reflectance, or measure the installed surface. A clean sample will read higher than the same surface after a few years of dirt. So say whether a figure is initial or aged.

Record whether your coefficient is measured, supplier-reported or assumed. Keep the source with the project file so a reviewer can trace it.

Concrete vs asphalt

PVsyst lists concrete at 0.25 to 0.35 and dry asphalt at 0.09 to 0.15. Wet asphalt is 0.18. Even the lowest concrete value (0.25) sits above the highest asphalt value in the table (0.18, wet). Taking midpoints, concrete at 0.30 reflects about 2.5 times as much as dry asphalt at 0.12 (0.30 / 0.12 = 2.5). That matters for bifacial rear-side input. It also matters for a ground-mount site that will be paved.

What albedo value should you use in PVsyst?

PVsyst’s usual value is 0.20, which is its default. PVsyst says the best value for a specific situation comes from direct site measurement. It also says that, apart from vertical planes, the value is not critical, because the albedo part is small in the incident global irradiation.

For row-based monofacial systems such as ground plants, only the first row sees the albedo. Monofacial modules collect light on the front only. PVsyst notes that the shading factor on that component is (n-1)/n, where n is the number of rows. For 100 rows that factor is 0.99.

The exception is bifacial work. PVsyst’s own bifacial documentation says the ground albedo is very important there. It says to estimate it with care for each system. SAM’s PVWatts and detailed photovoltaic models use the weather file’s albedo if it has one. Otherwise they use a default of 0.2, per the SAM weather-data documentation. SAM (System Advisor Model) is a solar modeling program.

Ground-reflected irradiance formula

For flat ground that reflects light evenly in all directions, the front-plane formula is:

Ground-reflected irradiance = albedo × GHI × (1 − cos(tilt)) / 2

GHI is global horizontal irradiance in W/m². That is the sunlight power on a flat, horizontal surface. Tilt is measured from horizontal. Use radians when your software expects radians for the cosine. This is the front-plane term for an unobstructed tilted plane. PVsyst’s albedo model documentation uses the same expression in all of its transposition models. These models convert horizontal sunlight to tilted-plane sunlight. It is not a rear-side bifacial calculation or an annual energy formula.

Worked example at 30 degrees

Assume GHI is 800 W/m², tilt is 30 degrees and the ground is uniform with no obstruction. The geometric factor is (1 − cos 30°) / 2 = (1 − 0.86603) / 2 = 0.06699. This matches the 6.7% PVsyst gives for 30°. Multiplying by 800 W/m² gives 53.59 W/m² per unit of albedo.

Going from 0.20 to 0.80 quadruples this one component, from 10.72 to 42.87 W/m², a difference of 32.15 W/m². Total plane-of-array irradiance (the sunlight on the tilted panel surface) has other components. So this is not a fourfold production increase. PVsyst gives the geometric factor as 0.8% at 10°, 3% at 20°, 6.7% at 30°, 14% at 45° and 50% at vertical. It is zero for a horizontal plane.

Keep units visible in the calculation. Entering 20 in a field that expects a fraction of 0.20 is a hundredfold input error. Check whether a tool asks for a decimal coefficient or a percentage before you import a spreadsheet.

Monofacial and bifacial systems need different checks

Monofacial modules collect useful light through their front. Bifacial modules can also use rear irradiance. For that, the ground must receive light and the reflected light must reach the module. Height, pitch, tilt, ground shading, rear obstructions and module bifaciality all change the result. Rear light can be uneven, which adds mismatch (modules producing unequal current). DC current limits and inverter clipping (the inverter cutting off extra power) can also affect delivered energy. PVsyst’s bifacial model explains these separate irradiance and electrical steps.

PVsyst states that the bifacial irradiance contribution, and so the bifacial gain, is directly proportional to the albedo of the ground below the array. So relative to a 0.20 surface, a 0.30 surface gives 1.5 times the ground-reflected input to the rear side. A 0.50 surface gives 2.5 times and a 0.80 surface gives 4 times:

These are ratios of the albedo values (0.30 / 0.20, 0.50 / 0.20, 0.80 / 0.20). They are not energy-gain percentages. The gain in kWh depends on height, row spacing, shading and bifaciality. So run the model for the real layout.

For snow, Sandia’s PVPMC says the difference between dry concrete or asphalt (about 0.2) and fresh snow (about 0.8) can boost PV output by 5 to 10% if the array stays snow free. That is read from a plot for a latitude-tilt array in Albuquerque, New Mexico, in August. So it is one case, not a general figure.

A white roof does not by itself justify a bifacial premium. Compare a defined module and mounting layout against a consistent baseline, with the same weather file and output boundary. In the report, keep three things apart: increased reflected irradiance, modeled DC output and delivered AC energy. For the broader equipment and layout decision, use the bifacial solar panel design guide, or the bifacial solar technology hub for an overview.

On trackers, PVsyst notes that albedo shading is a significant contribution to diffuse irradiance loss even with backtracking (rows turning back to avoid shading each other). The solar tracker comparison covers the layouts.

Do not apply a far-ground row-shading factor to every rear-side reflection. Inter-row ground and distant terrain are different contributions. Write down which component a claimed loss applies to before you use it in a sensitivity calculation.

Questions to ask for each site type

Use these as survey prompts. Array geometry must also meet structural, access and installation needs, whatever the albedo. The inter-row spacing guide explains the geometry inputs to record.

Measuring albedo on site

An albedometer is two solarimeters. One measures horizontal irradiance. The other, turned the other way, measures the irradiance coming from below. Their ratio is the albedo. PVsyst says site measurements should be long-term. The instantaneous value depends on the height of the sun, whether the ground is wet or dry, and how weathered it is (PVsyst albedo model). Follow the installation and calibration instructions for your instrument.

For a usable measurement campaign, record the items below. Do not rely on an unexplained sensor-height rule:

• Sensor models, calibration status, sensor direction and units.
• Mounting position, surface footprint and obstruction or support shadows.
• Time sync, logging interval and how you treat data quality.
• Surface condition, rain, plants and snow during measurement.
• Cleaning and inspection records, missing data and campaign coverage.

Measure a surface that represents the planned project. Grass measurements next door do not tell you the reflectance of replacement gravel. Avoid dividing by unreliable incoming irradiance near darkness. Define quality filters and keep the record of rejected data. A short clear-day survey is not an annual record. So size the campaign to the uncertainty you need to cover.

Hypothetical instantaneous reading: reflected irradiance of 120 W/m² divided by incoming irradiance of 600 W/m² gives 0.20. Both readings must describe the same time and the same measurement boundary.

Combining readings also needs a clear definition. Suppose two equal-length valid periods have incoming/reflected irradiation pairs of 500/100 and 100/40 Wh/m². Their individual ratios are 0.20 and 0.40. The arithmetic average is 0.30. The ratio of accumulated reflected to incoming irradiation is 140/600 = 0.2333. Report which statistic you used. Neither one is automatically a good annual input for a bifacial model.

Seasonal inputs, weather files and software settings

Snow, moisture, vegetation and surface weathering can change albedo. Snow on the ground can increase reflected irradiance. Snow on modules adds a separate loss. A model should show both effects. Do not assume that every snowfall improves net production. Sandia’s PVPMC albedo guidance discusses how much changing ground reflectance matters.

In PVsyst, project albedo describes the terrain visible in front of the installation. Bifacial albedo describes the surface below it. Both can use annual or monthly inputs. They need not be equal, for example when a roof treatment differs from the surrounding terrain. Keep a screenshot or export showing which field you changed.

For SAM’s detailed photovoltaic model, the weather-data documentation says you can choose on the Location and Resource page. You can use the weather file’s albedo or monthly values you enter. Check which option is active and inspect the resulting time series.

A monthly profile helps when its seasonal values have a solid basis. Twelve invented values are not better evidence than one disclosed assumption. When you have only limited information, run a plausible range of sensitivities and describe the limit. Compare weather period, module selection, geometry, losses and output boundary the same way between runs.

Satellite or regional data can support screening. Inspect the dataset’s spatial footprint, time resolution and missing-data treatment. Also check how it defines reflectance. A regional pixel may mix surfaces that are not under the array. Roof imagery can guide a survey. It does not measure broadband solar reflectance.

Roof reflectance and Solar Reflectance Index

Request solar reflectance for the exact roof product, including whether the rating is initial or aged. Solar Reflectance Index (SRI) combines reflectance with thermal emittance (how well a surface gives off heat) to describe heat rejection. It is not itself a fraction of sunlight reflected. Values can fall below zero or exceed 100. The Cool Roof Rating Council says SRI values typically range between 0 and 100, with particularly hot materials negative and particularly cool materials above 100. Module glass reflectance is a separate topic, covered in anti-reflective coatings for solar panels.

Do not convert SRI into albedo using a fixed threshold or by dividing by 100. Also keep a cool-roof building-energy assessment apart from a PV production assessment. The underlying inputs and useful outputs differ. Before you propose changes, confirm coating compatibility, warranty and required approvals with the responsible parties.

Can you raise albedo on purpose?

Treat a reflective surface as a proposed design scenario. Establish baseline and enhanced reflectance with evidence. Keep the same simulation boundary and calculate the extra delivered energy. Include installation, replacement, inspection and maintenance costs from current project quotes. In the project review, look at drainage, plants, wind and glare. Also look at roof or ground fit and environmental rules.

Do not promise a standard payback. Do not prescribe a universal gravel depth, reflector placement or maintenance interval. Reflectance, geometry and the working condition of a treatment must stay credible over the forecast period. Run a sensitivity case where enhancement performance declines. State which costs and losses are included.

For a customer-facing estimate, carry the surface assumptions and uncertainty into the solar proposal workflow. To see energy-yield modeling on a project of your own, book a SurgePV demo and ask which albedo inputs and output boundaries the workflow supports.

What to hand over for design review

Provide the surface description and dated evidence. Add the coefficient or time profile you chose. Add the active software fields and the module and geometry inputs. Add the baseline and sensitivity results and the delivered-energy boundary. Explain what remains assumed and what needs site checks. This makes the albedo choice easy to review.

Frequently Asked Questions

What is the albedo value for concrete in solar design?

PVsyst lists 0.25 to 0.35 as a usual concrete reference range. Use it as a first assumption, not as a measured property of every concrete surface. Check the actual finish and condition when the effect on production is large enough to matter.

How does albedo affect bifacial solar panel output?

Bifacial panels collect light on both sides. Albedo changes how much reflected light (irradiance) reaches the rear side. Delivered energy also depends on geometry, shading, module bifaciality, mismatch and electrical limits. A percentage change in albedo is not the same percentage change in annual plant output.

What albedo value should I use in PVsyst for a grass field?

PVsyst lists grass at 0.15 to 0.25 and fresh grass at 0.26. Its general default of 0.20 is not just for grass. Write down the actual ground cover and seasonal assumptions. Then test how much the input changes the result.

Can snow increase solar panel energy production?

Snow on the ground can increase reflected irradiance. Snow covering the modules is a separate production loss. Check both effects for the site and period. Do not apply one universal annual gain.

How do you measure albedo on a solar project site?

Measure incoming and reflected irradiance at the same time. Use properly installed horizontal pyranometers (sunlight sensors). Then divide reflected by incoming irradiance. Record calibration, surface footprint, shadows, quality filters and campaign coverage. Follow the instruments you chose and the project measurement plan.

What is the difference between albedo and Solar Reflectance Index?

Albedo is reflected sunlight as a fraction. SRI (Solar Reflectance Index) combines solar reflectance with thermal emittance to describe how well a surface rejects heat. SRI can be below zero or above 100. SRI alone does not give you an albedo input.

What is a good albedo value for PVsyst?

PVsyst’s default is 0.20, which it gives as the usual value. It lists 0.14 to 0.22 for urban environments and up to 0.8 for snow cover. For a bifacial system, PVsyst says the ground albedo is very important and should be estimated with care. The best value comes from site measurement.