Vertical Solar Panels in Snow

A panel tilted for the summer sun is aimed at the wrong sky in December. At noon on December 21, a standard formula puts the sun just 1.6 degrees above the horizon in Fairbanks, Alaska. In Golden, Colorado, it reaches 26.6 degrees. Researchers at the University of Alaska Fairbanks are testing a different answer: panels standing straight up, facing east and west.

The idea is newer than it looks, and the studies behind it do not all agree.

The old answer: aim the panel at the noon sun

Shine a flashlight at a wall. Held square to the wall, it makes a small, bright circle. Held at a slant, the same light stretches into a larger, dimmer oval. A solar panel meets sunlight the same way. PVEducation, a solar teaching site, turns that into a rule. Add the sun’s height above the horizon to the panel’s tilt. The result sets what share of the beam the panel catches.

Tilt is counted from flat ground, so 0 degrees is flat and 90 is upright. The share reaches 100% when the panel faces the beam head-on. At noon that happens when tilt equals 90 degrees minus the sun’s height.

The sun’s noon height comes from latitude and date. PVEducation gives it as 90 degrees minus the latitude, plus the sun’s seasonal offset, called declination. That offset swings from about minus 23.45 degrees in December to plus 23.45 degrees in June. The table below applies the formula at four latitudes.

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Sun height at local solar noon, and the tilt that faces it head-on. Calculated from PVEducation’s formulas. Tilt is measured from flat ground.

At 60 degrees north, a panel standing 84 degrees from flat, almost upright, meets the December noon sun head-on. In June the same site wants 37 degrees. A fixed panel is stuck with one angle, and winter and summer want different ones. At 69 degrees north the noon sun never clears the horizon on December 21, so no tilt catches direct beam that day.

So what does a single angle give up? For one fixed angle, PVEducation’s rule is that yearly output peaks when tilt equals latitude. It adds that steeper tilts suit large winter loads, meaning homes that use more power in winter. The off-grid cabin guide on ecotechnews.world gives the same rule of thumb.

Take 65 degrees north and the noon beam in December. A vertical panel facing south catches all of it. A panel tilted at the latitude, 65 degrees, catches 92%, and one tilted at 40 degrees catches 66%. In June the order flips: 100% for 40 degrees, 92% for 65 and 66% for vertical. These shares say nothing about how much light there is, and they assume a panel facing due south. East-west vertical panels, covered below, use the sun differently.

A Swedish model gives a sense of the stakes. Wang and Laumert at KTH Royal Institute of Technology tried every tilt from 0 to 90 degrees in 0.1-degree steps. Their weather data covered ten years (2012 to 2021) at Hammarby Sjöstad, Sweden. KTH’s summary of the Applied Energy paper says the best fixed tilt gave about 4.8% more generation than a 15-degree commercial angle.

Adding snow moved the best angle by up to 7.8 degrees, depending on the year’s weather. In the model, snow can cut generation by 14.7%. Snow removal agents improved performance by 0.1% to 2.3%.

What changed: panels that collect light on both faces

The old rule assumed a panel with one working face. Many panels now have two. A bifacial panel collects light on its front and its back. A 2024 overview in PV Tech puts numbers on how common they are. Its authors work at Sandia National Laboratories, the US National Renewable Energy Laboratory and two other organizations. Citing the industry roadmap ITRPV, they say 90% of solar cells made in 2024 are bifacial. About 62% of modules are made as bifacial modules.

One layout that bifacial panels make possible is a vertical row with one face toward the east and one toward the west. A 2021 report from the International Energy Agency’s solar program (IEA PVPS) calls these arrays especially suited to bifacial panels. It lists a wider generation period that better matches typical loads, and little soiling, meaning dirt build-up on the glass.

Vertical bifacial panels also have a performance advantage at high latitudes, the report says. Its reason is the wide variation in the sun’s compass direction, called azimuth, during summer.

Ground helps the back face too. Albedo is the share of light a surface bounces back. The same report puts ordinary ground covers at an albedo of 0.2 to 0.3. Over them, fields of panels that turn to follow the sun generally gain less than 10% from the back face. When snow covers the ground, the report says, those gains increase significantly.

A 2019 presentation by Laurie Burnham of Sandia adds numbers from Fairbanks. East-west vertical arrays there made 5% to 20% more energy than traditional designs, it reports. The slide credits a Sandia study.

Henry Toal of the Alaska Center for Energy and Power (ACEP) made a bolder claim in a 2025 news article. East-west vertical bifacial panels can be “just as productive” as traditional ones, he said. He meant south-facing tilted panels at high latitudes. ACEP tests such panels on the Fairbanks campus, along a north-south line, so one face looks east and the other west.

Predicting their output is another matter. Toal’s team tested five computer models of sunlight on vertical bifacial panels against field data from Golden and Fairbanks. The article says none predicted well in cloud or snow, and Alaska was worse. It lists monitoring snow levels and using heated sunlight sensors among ways to improve accuracy at high latitudes.

What field tests and simulations found

A 2024 simulation in Frontiers in Built Environment covered three low-rise neighborhoods in Helsinki, Finland. On east- and west-facing roofs, vertical bifacial panels on the roof ridge beat ordinary panels lying parallel to the roof by 20% to 30%. On a south-facing roof the ordinary panels won, with 1,000 kWh/kWp against 920 for one row of vertical panels. The unit kWh/kWp means kilowatt-hours made per year for each kilowatt of panel rating.

Walls and open ground fared worse. Vertical systems there lost 30% to 70% against roof-ridge ones. The authors say trees and dense layouts limit suitable sites, and that snow-covered ground reflects a lot of light.

SINTEF tested several setups at a field lab in Trondheim, Norway. They included vertical east-west and south-north modules, fixed south-tilted modules and a two-axis tracker. The tracker turns to follow the sun. The 2024 paper reports several output peaks a day. Bifacial modules respond more to scattered light, and snow losses are larger for tilted ones. The abstract gives no figures.

The boldest number comes from a master’s thesis at UiT in Tromsø, near 69 degrees north. Over the winter of 2022 to 2023, a vertical bifacial setup had a specific yield 230% higher than a 10-degree monofacial one. Specific yield is energy made per kilowatt of rating. The author credits snow shedding and reflected light. It was one site and one winter, with different panel types, and the thesis is not peer reviewed.

Each row has different conditions, so the numbers cannot be compared with one another. Results are as given by each source.

Snow, the problem still open

Snow blocks light, and estimates of the loss vary widely. A research project led by Sandia National Laboratories puts it at 1% to 15% a year. Single months can lose as much as 90%. The project’s summary page adds that systems shedding snow quickly make more energy available to the grid.

Burnham’s 2019 presentation names sliding as the main way snow leaves a module, and says the frame can hold it back. In one test, frameless modules made 13% more energy than framed ones during December 2018. The slides also say vertical modules may shed snow better, though shading could be an issue. That last point is an expectation, not a measured result.

Erin Whitney of ACEP gave a talk at a 2021 workshop of the same IEA solar program. Her slides say snow has a significant effect on production at high latitudes. They single out spring, naming March and April. Clearing, coatings, heating and vertical panels are on her list of fixes, each to be weighed against cost.

ACEP’s 2024 case study of three Fairbanks home systems adds local detail. Fairbanks averages around 5½ feet (1.7 m) of snow a year. Over 21 months, tilted arrays usually did better across a year than arrays lying along a low-slope roof. In spring the roof-parallel array on an 18-degree roof sat mostly under snow.

In February 2026 the IEA published a report on solar in the Greater Arctic Region. Its executive summary calls bifacial systems “particularly advantageous in high-latitude regions” and says vertically oriented ones, often east-west, reduce snow coverage. It adds that snow shedding works better with higher tilt and clearance under the arrays. Tracking systems are less recommended, it says, because of operating challenges in the cold. The summary gives no tilt angle and no loss figures.

Cold has an upside too. The same report says lower temperatures raise panel efficiency. It gives a median degradation rate of 0.37% a year for systems above 59 degrees north. Across the continental United States the figure is 0.75% a year. Degradation is the yearly loss of output as panels age.

Why the studies do not agree on one angle

Those rows differ in more than place. The Tromsø thesis set a vertical panel of one type against a 10-degree panel of another. Tilt cannot be separated from panel technology there. Helsinki is a simulation and KTH a model. ACEP’s case study compared mostly roof angles.

Timing differs too. Vertical east-west panels move output toward morning and evening. The Helsinki study shows this in its hourly profile, and SINTEF says mixed orientations match consumption better. Standard panels make most of their power near midday. Heating and cooling demand often peaks early or late, as the ecotechnews.world piece on heat pumps and rooftop solar notes.

Vertical solar is also being discussed for city buildings, such as the ultrathin solar cells for glass facades covered on ecotechnews.world.

What is known and what is not

The geometry is settled: at high latitudes the winter sun sits so low that steep and vertical panels face it more squarely. Bifacial panels have become the norm in manufacturing. The IEA and several studies in Alaska, Norway and Finland report advantages for vertical bifacial panels in particular setups. Snow costs 1% to 15% of yearly output in one estimate, and far more in single months. What no source settles is one best angle for every site. The models struggle in cloud and snow. The sources read here give no measured results for snow-clearing coatings or heating. The Sandia and ACEP snow projects and further field data from Nordic sites are the next things to watch.

Frequently Asked Questions

What is the best solar panel angle in winter?

By geometry, a panel faces the noon sun head-on when its tilt equals 90 degrees minus the sun’s height. At 60 degrees north on December 21 that is about 84 degrees. No single fixed angle serves every season, and snow adds its own effects.

Should solar panels be steeper in northern regions?

Yes, for yearly output. PVEducation says output peaks when tilt equals latitude, so higher latitudes point to steeper tilts, and steeper angles suit large winter loads. The IEA’s 2026 Arctic report adds that snow sheds better from higher tilt angles.

Do vertical solar panels work in snow?

The Tromsø thesis, the Trondheim field lab and the Helsinki simulation all report advantages for vertical bifacial panels in some conditions. Helsinki found ordinary panels better on a south-facing roof, and the models tested at Fairbanks struggled in cloud and snow.

What are bifacial solar panels, and how common are they?

Bifacial panels collect light on both faces. In a vertical east-west setup, one face works in the morning and the other in the afternoon. Both can catch light reflected from snow. A 2024 overview citing the ITRPV roadmap says 90% of cells made in 2024 are bifacial.

How much electricity does snow cost a solar system?

A Sandia-led project estimates 1% to 15% a year and as much as 90% in a single month. A KTH model for a Swedish site put it at 14.7%. Tilt, climate and how fast snow slides off all play a part.

Why do vertical panels make two peaks a day?

The east-facing side catches the morning sun and the west-facing side the afternoon sun. ACEP and SINTEF both describe the double peak.

What does kWh/kWp mean?

It stands for kilowatt-hours made per year for each kilowatt of rated panel power. That lets systems of different sizes be compared, as in the Helsinki study.

Acknowledgment of AI

Content developed using AI technology, reviewed to ensure clarity, coherence, and accuracy before publication