Solar Power Beyond the Rooftop

Most people picture solar power as panels on a roof or a field of panels in the countryside. Those are still the biggest uses, but solar cells now show up in a surprising range of places, from balconies and reservoirs to farms and spacecraft. The cost of solar panels has fallen by roughly 90 percent since 2010, according to the International Renewable Energy Agency, which is a big reason for the spread.

Balconies and small homes

Plug-in "balcony solar" kits are small panels that hang on a railing and plug into a regular outdoor socket, feeding power into the home's circuit. They've become popular in Germany, where rules were relaxed in 2024 to allow systems up to 800 watts with simpler registration. They suit renters who can't install a roof system. Rules on plug-in solar vary a lot between countries and US states, so check local regulations before buying.

Floating solar

Panels mounted on floats can be installed on reservoirs, ponds and lakes. The water keeps panels cooler, which slightly improves efficiency, and the panels reduce evaporation. Floating solar is growing fastest in Asia, where land is scarce, and is being used on water treatment ponds and hydroelectric reservoirs elsewhere.

Agrivoltaics: solar and farming together

Agrivoltaics means combining solar panels with crops or livestock on the same land. Panels are raised high enough for farm work underneath or spaced in rows. Sheep grazing under solar panels is increasingly common because the animals keep the grass down. Research at sites including the University of Arizona has found that some crops, such as certain peppers and tomatoes, can do well in the partial shade, especially in hot, dry climates, while the plants keep the panels cooler.

Transport

• Space: solar panels have powered satellites since the 1950s, and the International Space Station runs on large solar arrays.
• Vehicles: a few cars and many campervans use solar panels to top up batteries, though a car-sized panel adds only modest range.
• Boats: sailing yachts and some ferries use solar for onboard power.
• Infrastructure: solar-powered road signs, parking meters and railway signals avoid running power cables to remote spots.

Portable and off-grid solar

Folding solar panels paired with portable battery stations are popular for camping, vans and emergency backup. Solar home systems and lanterns provide electricity to millions of people in regions without reliable grid power, often replacing kerosene lamps, which are a fire and health hazard.

Built into buildings

Building-integrated solar replaces conventional materials with solar ones: roof tiles, facades and even windows. These are more expensive than standard panels and usually less efficient, but they appeal where appearance matters. Solar carports, which shade parked cars and generate power, are a more practical option for many businesses.

How efficient are panels?

Typical residential panels today convert around 20 to 23 percent of the sunlight hitting them into electricity. Laboratory cells have gone much higher, particularly multi-layer "tandem" cells that combine silicon with a newer material called perovskite. Efficiency matters most where space is limited; on a large field, price per watt usually matters more.

Solar in cold and cloudy places

Solar panels work in cold weather; in fact, they're slightly more efficient at lower temperatures. What reduces output is shorter days, low sun angles and cloud cover. Germany, which has a fairly cloudy climate, generates a significant share of its electricity from solar, showing that sunshine-rich climates aren't required. In snowy areas, panels are tilted so snow slides off, and output drops while they're covered.

What happens at the end of a panel's life

Panels typically come with performance warranties of 25 years or more and lose a small fraction of their output each year. Large numbers of panels will reach end of life in the coming decades. Most of a panel by weight is glass and aluminum, which are recyclable, and the European Union requires producers to finance collection and recycling of old panels. Recycling capacity in many other countries is still being built up, and extracting silver and silicon economically remains a challenge.

Things to know before buying solar

• Output depends heavily on orientation, shade and local climate. A shaded panel can produce a fraction of its rated power.
• Batteries add cost but let you use solar power in the evening or during outages.
• Incentives, net metering rules and installation permits differ widely by location, so the financial case varies.
• Quality installers provide estimates based on your actual roof and electricity use, not just panel wattage.