What if solar panels became much more efficient?

Solar panels catch sunshine and make electricity.

But they only use a small part of the sunshine. What if they could use much more of it?

A solar panel turns sunlight into electricity, but it cannot use all the sunshine that lands on it. Some of the light bounces off or passes straight through, and only part of the light's energy becomes electricity. The share that becomes electricity is called the panel's efficiency.

So what if solar panels became much more efficient? Would they make a little more electricity, or a lot more? Could a house need fewer of them? In this lab you can turn up a panel's efficiency and find out.

Efficiency is the fraction of incident solar power a cell or panel converts to electricity. PVEducation notes that it is measured under standard conditions, sunlight of 1 kW/m² at a cell temperature of 25 °C, so different devices can be compared fairly.

This lab asks what a large jump in efficiency would mean in practice. It keeps the panel, the place, the date and the weather fixed, and changes efficiency alone: from 20 percent to 30 percent.

In Olly's lab, a solar panel sits in the sunshine on a summer day.

It makes the most electricity at midday, when the sun is high.

Our model panel is 1.7 square meters and 20 percent efficient. It sits on a clear 21 June at latitude 40 degrees north, tilted 30 degrees toward the south.

At solar noon it makes 310 watts. Over the whole sunny day, from sunrise to sunset, it collects 2.32 kilowatt hours of energy. The U.S. Energy Information Administration says the best modern panels are now approaching 25 percent efficient. Our model's 20 percent sits between the 15 percent of 2015 and today's best.

The model computes the direct beam from the sun's position and a clear-sky air-mass formula, takes the component that strikes the tilted panel, and multiplies by area and efficiency: P = beam × cos θ × A × η.

For A = 1.7 m², η = 20%, tilt 30°, latitude 40° N, 21 June and a clear sky, noon power is 310 W and the day's energy 2.32 kWh over 14.8 hours of daylight. EIA reports commercial module efficiency below 10% in the mid-1980s, around 15% by 2015, and approaching 25% for state-of-the-art modules today.

Now Olly makes the panel much better at catching sunshine.

Same sun, same panel size. But it makes much more electricity!

Now turn the efficiency up to 30 percent. The sun, the sky and the panel's size have not changed at all. But noon power jumps from 310 to 465 watts, and the day's energy from 2.32 to 3.48 kilowatt hours: half as much again.

That also means a smaller roof could do the same job. In the model, 15 square meters of 20 percent panels and just 10 square meters of 30 percent panels both make 20.50 kilowatt hours on this sunny day.

Because output is proportional to η, raising efficiency from 20% to 30% multiplies every output by 1.5: noon power 310 → 465 W, daily energy 2.32 → 3.48 kWh.

Equivalently, the area needed for a given output scales as 1/η. In the model, 15 m² at 20% and 10 m² at 30% each give 20.50 kWh, and 1.1 m² at 30% (2.25 kWh) nearly matches the original 1.7 m² at 20%. The jump to 30% is beyond today's commercial modules, which EIA describes as approaching 25%.

Sunshine brings energy to the panel. The panel keeps only part of it as electricity.

A better panel keeps a bigger part. So it makes more electricity from the same sunshine.

The sunshine reaching a panel carries a fixed amount of energy. Efficiency decides what share of it becomes electricity. Make that share bigger and you get more electricity from exactly the same light.

Our model is simple. It counts only direct sunshine, not light scattered by the sky. Its panel never gets hot, so its efficiency never drops, and it ignores wires and other equipment that waste a little energy. Real panels in hot sun make somewhat less.

With the beam, angle and area fixed, P = beam × cos θ × A × η is linear in η, so efficiency gains translate one-for-one into output gains. What limits real η is physics: EIA explains that photons can reflect off a cell, pass through it or be absorbed, and only absorbed photons generate electricity.

Model limits: direct beam only (no diffuse skylight or ground reflection), η constant with temperature and light level, and no wiring or inverter losses. PVEducation notes that rising temperature reduces a cell's voltage, so real panels in strong sun run below their rated efficiency.

Scientists keep making better solar cells. Some special cells already catch about half of the sunlight's energy!

They are used for things like satellites.

Solar panels have improved a lot. The U.S. Energy Information Administration says ordinary panels were less than 10 percent efficient in the mid-1980s, about 15 percent by 2015, and the best are now approaching 25 percent. Experimental cells and special cells, such as those for space satellites, have reached nearly 50 percent.

The National Laboratory of the Rockies, a U.S. Department of Energy lab, keeps a chart of the best research cells since 1976. Every record on it must be confirmed by an independent test lab. Whether everyday rooftop panels might one day reach 30 percent is something researchers are working on, not a sure thing.

EIA traces commercial module efficiency from under 10% in the mid-1980s to around 15% by 2015 and close to 25% for state-of-the-art modules, while experimental and niche cells, such as those on satellites, have achieved nearly 50%.

The National Laboratory of the Rockies maintains the Best Research-Cell Efficiency Chart from 1976 to the present (last updated 14 August 2026), grouping about 28 subcategories into multijunction, gallium arsenide, crystalline silicon, thin-film and emerging technologies; each record must be confirmed by an independent, recognized test lab. The chart tracks research cells made in labs, not the panels sold for rooftops.