EnergySolar electricity and bad weather

Solar electricity and bad weather

What happens to my solar panels and my energy production in bad weather? This is a pretty common question people have about solar energy. It’s also something thrown around by misinformed solar skeptics and proponents of fossil fuels, saying solar energy is worthless because if it’s cloudy, your power goes out.

Part of that is a legitimate question—obviously, solar panels need full sunlight to work at full efficiency. But that doesn’t mean that an errant cloud is going to shut down your day. A huge part of any intermittent energy production like wind and solar is energy storage, and every photovoltaic system comes with batteries to store energy for nighttime or cloudy days. So how much does weather affect the efficiency of your system? Well, it depends. Let’s go through all the scenarios and how they affect your energy production

Will my solar panels work at night?


There’s not really much more to it. Your panels use the sun’s energy to produce electricity.

What happens in full sun?

On a perfectly sunny day, and with your average energy consumption, you can expect your system to produce to the full capacity of your batteries and power your home comfortably.

There’s a drawback though—due to the technology involved, solar panels have an optimal temperature where the energy production is at its peak. In extreme heat, the energy efficiency actually drops. It’s not quite what you’d expect, but that’s because, like a leaf using photosynthesis, solar panels work from the light energy hitting the panels, and not heat.

What happens to my solar power during cloudy weather?

On moderately cloudy days, you can expect your energy production to drop by at least half. It really depends on the amount of clouds in your area, but assuming you have a day of complete cloud cover from morning until night, your panels will produce about ,10-25% of your regular energy production for the day. This is also why solar tends to be a better option for regions that experience more days of sunlight. In Hawai’i, for instance, we average about ,240 days of sunshine per year, whereas Seattle averages only about ,150 days of sunshine per year. So while obviously your energy production will dip during cloudy weather, it doesn’t dip down to zero. And on a day with just a few clouds floating through the sky, your system will be able to keep up just fine.

Can rain affect my solar panels?

On rainy days, you’ll see the same efficiency dip as you’d see on any other cloudy day, but the benefit is that the rain will help wash away accumulated dust and dirt that could be impacting the production of your panels even on sunny days. Dirty solar panels can be 5% less effective than clean ones, so bring on the occasional rain! However, rain alone may not be enough to wash your panels—it may be worth inspecting them once or twice a year to see if they need a better scrub. If there’s a buildup of dust or grime, it’s a good idea to use a soft sponge or towel and some soapy water to clean them up.

Hail, wind, and extreme weather events

With proper installation, your solar panels should be able to withstand quite a lot. Most panels are rated to withstand hail to a certain extent, and should also be able to hold up against even hurricane-force winds. If your roof is still attached to your house, your panels will still likely be attached to your roof! That doesn’t mean your system is invincible, and after extreme weather events your system may need to be serviced, but they can be much more resilient than you’d expect.

Snow and solar energy

In Hawai’i, this isn’t something we have to think about very often. But if you live in a colder climate, you might be thinking about whether it’s worth it to get solar, and what happens when your roof is covered in snow, since some storms can leave snow that sticks to a regular roof for days or weeks.

If there’s such huge amounts of snow that the panels are completely buried, then energy production will be impacted. But for an average snowfall that leaves an inch or so, there won’t be too much of an impact at all. Sunlight is able to penetrate the thin white layer and make it to the panels.

The other good thing is that solar panels are slippery and dark, meaning snow will have a harder time sticking and will melt faster than on conventional roofing surfaces. And like rain, a little snow now and then will help to clean the surface of your panels as it melts and slides off.

As long as your system is installed properly to account for the added weight snow might bring, you shouldn’t have any problem. You can expect less energy production while the panels are covered, but once the sun comes out again you’ll be back in the green.

What happens if bad weather affects my solar energy production?

As mentioned, most solar customers today get a system installed that includes power storage of some kind. But the other thing to remember is that most people who get solar panels installed are not actually truly off the grid. As a Hawai’i resident, your system will still be connected to the HECO grid, so on days when your panels don’t produce as much energy, or on days when your usage is high, you’ll be pulling electricity from the public utility to make up the difference.

Ideally in the future the energy we use from the grid will be renewable as well, and if Hawaii hits its energy independence goals, that could happen by 2045. Until then, solar customers are doing their part to bring us to our goal.