Do Solar Panels Work On Cloudy Days? (Cooler Efficiency!)

Many people mistakenly believe solar panels only work on clear sunny days when this is not the case. They are designed to produce electricity regardless of the weather conditions using the available solar energy on the day.

Solar panels work on cloudy days as they don’t require direct sunlight to generate electricity; they will not produce electricity when cloudy or rainy weather. The solar radiation received and absorbed during inclement weather will be less.

The key elements of this discussion are :

  • How solar panels function to create electricity
  • Why direct sunlight is best for solar panels
  • The effect of weather conditions on electricity generation from solar panels
  • How the seasons can affect solar panel efficiency
  • What other factors influence solar panels & power generation

Let’s explore these in more detail to understand how solar panels work when the sun is not shining.

Elements Of Solar Power Plants Against The Sky With Clouds. - Sol Voltaics: Solar Panel Information
Elements Of Solar Power Plants Against The Sky With Clouds.

How Do Solar Panels Work?

Solar panels create electricity by using the sun’s radiation to split off electrons in the photovoltaic cells found inside the silicon panels. This creates a flow of electrons through the panel resulting in an electric current.

Solar panels are composed of silicon panels with PV cells inside them. When sunlight hits them, energy in the light in the form of photons is absorbed, and the photons release electrons that are then absorbed through bus bars on the side of the panel and transmitted through wires as DC electric current.

Using boron and phosphorous to create positively charged and negatively charged semiconductors, the different charges create an electric field between them, allowing the electrons to become an electric current.

As the electrons hit the metal plates, they are converted into a current and transmitted by wires to the inverter, which converts the DC to AC, then used to power the home.

Since sunlight carries photons all the time, there are still photons present in sunlight on cloudy days, and this is how solar panels can still generate electricity when there is no direct sunlight.

When there is bad weather and little to no sunlight, or it is nighttime, the panels cannot produce electricity, and this is where the ability to store that energy and then use it is utilized.

Storing Energy In A PV System

If the PV system has battery storage capacity, the current is also used to charge the batteries using excess energy generated during the day.

  • For example, if the house has a 10kW PV system and only 6kW is utilized, the remaining 4kW would be diverted to the batteries for storage.

The batteries are used to supply power at night when the sun has gone down or during days when solar radiation levels are not sufficient to deliver the required load to the home. The DC from the batteries is then directed to the inverter and converted into AC for use in the home.

To understand how solar panels can work on cloudy days, we need to look at the level of solar radiation received during clear sunny days and how that level would drop on cloudy days.

Now that we know how solar panels work, we can look at cloudy days’ effect on generating capacity.

Solar Panels Covered Partially By Clouds
Solar Panels Covered Partially By Clouds

Why Solar Panels Work Best In Direct Sunlight

The energy received in direct sunlight provides optimum electrical generation capacity for solar panels, and during the peak sunlight hours, they produce the most electricity.

This is why the orientation and angle of the solar panels on your roof are critical.

During peak hours of direct sunlight, the photovoltaic cells in the panels receive the maximum light levels as the sun moves across the horizon and solar radiation levels decrease.

This principle also applies across the seasons. However, solar panels produce electricity in peak sunlight hours of winter as well, and it’s only when the weather conditions worsen that the levels of generation drop.

Whether it’s spring or mid-winter, if direct sunlight hits the solar panels, they will operate at optimum levels to generate electricity.

Solar Panel On A House Roof
Solar Panel On A House Roof

How Do Weather Conditions Affect Solar Panels?

As weather conditions worsen and become cloudy or rainy, the clouds block off sunlight, reducing the available intensity of sunlight reaching the solar panels. The denser the cloud cover, the less sunlight reaches the panels.

Depending on the density of the cloud cover, the efficiency of the solar panels can be reduced by as much as 70% or more, leaving the levels of electricity production very low and resulting in reduced power capacity to the home.

The PV system may revert to using supplied AC power where no batteries stabilize the supply. If there is no supplied power, the system may be unable to maintain all the appliances in the home.

How Much Less Power Do Solar Panels Produce On Cloudy Days?

Your solar panels would produce between 10% and 25% less electricity on partly cloudy days than on days with direct sunlight.

Where the cloud cover is more severe, your solar panels would only produce about 10%-30% of their capacity, which can, of course, negatively impact the power supply to your home.

To check whether your PV system is producing power, look outside and see whether shadows are cast, and if there are, then there is enough light for your PV panels to generate electricity.

Solar Panels On A Countryside Field With A Cloudy Sky. - Sol Voltaics: Solar Panel Information
Solar Panels On A Countryside Field With A Cloudy Sky.

Would Solar Panels Work In Rain Or Snow?

With rain and light snow, the cloud cover may not be heavy enough to eliminate all sunlight from hitting the solar panels and allowing them to generate electricity.

With more intense rain and snow, this would depend on the level of cloud cover involved.

Heavy snow could severely limit the panels’ level of sunlight. If the snowfall is consistent or you have blizzard conditions, this would curtail the ability of the solar panels to generate electricity.

Rain is good for your panels as it cleans off the accumulated dirt and dust on the glass, increasing their efficiency, especially if you haven’t cleaned them in a while.

Snow has another potential effect on solar panels as it can accumulate on the panels’ surface, block sunlight from reaching the PV cells, and stop electricity generation until it melts off or is cleaned.

The same would apply with consistent rain as this could also reduce the ability of the panels to generate electricity as they could keep layers of dirt and dust on the surface and reduce the levels of light coming in.

A Park For The Production Of Electricity With Solar Panels. - Sol Voltaics: Solar Panel Information
A Park For The Production Of Electricity With Solar Panels.

Does Electricity Generation Fluctuate With The Seasons?

Due to the changes in the sun’s position in winter and summer, there is a difference in the generation output of solar panels in winter and summer.

Splitting the year into two sections between March 21st (the Vernal Equinox) and September 21st (The Autumnal Equinox), there is a quantitative difference in generational capacity on solar panels.

On average, the summer months from September 21st to March 21st produce around 65% of the annual solar energy output, while the winter months account for the other 35%. Of course, these figures may vary depending on your summer and winter weather conditions.

Why Solar Panels Produce Less Electricity During Winter?

There are three reasons your panels produce less electricity during winter, and these same reasons would have some bearing as to why they produce less electricity on cloudy days.

The days are shorter during winter. This means lower levels and duration of sunlight during winter and coupled with inclement weather, would further reduce the sunlight levels reaching your panels.

In winter, the sun is lower in the sky, reducing the level of light reaching the panels even at midday when the sun is at its peak.

The typically more cloudy and overcast days that winters bring, along with shorter days and the sun’s lower position in the sky, compound the effect of reduced electricity production.

Can Cloudy Days Increase Your Energy Costs?

The impact of reduced electricity production on your electricity costs would be negligible as the effect of cloudy days is factored into your system’s design.

When calculating your energy requirements, the designers of your system would work on the total annual energy requirements based on the annual consumption data extracted from your utility bills.

Using this as a guide, they would design a system that delivers more capacity during the spring and summer and builds up additional kilowatt-hours within the utility. This will see you through the months with lower sunlight levels.

Also, with the roof panels, the available space would often be effectively optimized to deliver more from your panels to accommodate cloudy days when sunlight is not at its maximum.

That said, persistent cloudy conditions could deplete batteries and electricity production over days or weeks.

With severe snowstorms across the US in recent years that continued for several days, these conditions could drain batteries and stop electricity production due to the lack of adequate sunlight.

If your system is grid-tied, then if you have poor weather, you can switch back to the grid supply until your energy generation system is back online. This would cost you some money, but it may not if you have net metering.

Net metering is where you feed electricity back into the grid and gain credits from the utility supplier. Then, if you need to access power when your PV system hasn’t generated enough power, you can offset your usage against credits on your account.

Solar Panels Producing Clean Energy On A Roof Of A Residential House With Cloud Reflections. - Sol Voltaics: Solar Panel Information
Solar Panels Producing Clean Energy On A Roof Of A Residential House With Cloud Reflections

Do Solar Panels Work Better In Hot Or Cold Conditions?

Colder temperatures make solar panels more efficient than warmer weather. Electrons are more active during colder weather, and this increased activity allows them to produce more electricity as the panels absorb more sunlight.

The higher the temperature, the lower the voltage produced, and for every degree above 77°F, the panel loses 1% of its efficiency. For every one degree below 77°F, the panel efficiency increases by 1%.

This is the case with most electronic devices; your solar panels are no different.

With this in mind, you may think that if cloudy days are more relaxed, the solar panels will work better, but this is not the case, as the yardstick is still the level of sunlight that reaches the panels that provide the best results.

Solar Panels Producing Clean Energy On A Roof Of A Residential House With Cloud Reflections. - Sol Voltaics: Solar Panel Information
Solar Panels Producing Clean Energy On A Roof Of A Residential House With Cloud Reflections

How Cloudy Days Can Cause A Production Spike

Under certain conditions, cloudy days can cause your electricity production to spike due to sudden increases in solar radiation intensity caused by the clouds!

As strange as that may seem, it is true. If you take a magnifying glass and focus the sun’s rays on wood or paper, the material will start to smolder or even burn. This is due to the heat being increased as it’s magnified.

Certain clouds passing in front of the sun create the same effect and can briefly but significantly boost the intensity of the light reaching your panels.

Water in the clouds acts as a magnifying glass for the sun’s rays, called the ‘edge of cloud’ effect. Cumulus clouds have that light, fluffy texture and the edges of those clouds have a ‘mist’ of water vapor that creates this effect.

Solar Panels Covered In Clouds. - Sol Voltaics: Solar Panel Information
Solar Panels Covered In Clouds.

What Are Other Elements That Affect Solar Panel Efficiency?

Clouds have the biggest impact on blocking sunlight to solar panels, but other things can also affect electricity generation.

When assessing your roof, you need to consider which direction it is facing, as north-facing is optimal as it would get the most sunlight throughout the year.

While not every house may face north, you can use ground-mounted solar panels that do face north to bolster the roof installation.

Another consideration is the trees around your home. While they won’t block the same levels of light as cloudy days would, the shadows they cast on your panels could well affect the generational capacity, and you may need to trim them down a bit to eliminate the effect of shadow.

Lastly, the inverter you use on the panels also affects system performance.

String inverters are the most common, with all the panels linked to a single inverter. If anyone’s panel is in the shade, then the whole system only operates on the power of the weakest panel.

Micro-inverters are installed on every panel, and if a cloud shades one, then only that panel’s output is diminished; the rest run at optimum.

Power optimizers mix both string and micro-inverters, negating the effect of shade from trees or clouds on the panel’s production capacity.

While micro-inverters and power optimizers are more expensive than string inverters, they provide optimal electrical production – even on cloudy days!

Resources

General Solar Panel FAQ

What Problems Do Solar Panels Solve?

In environmental terms, solar panels can potentially solve a handful of problems, including;
1. Air pollution
2. Water pollution
3. Greenhouse gases
4. Reduction in fossil fuel use

For individuals, solar energy allows you to become completely self-sufficient when it comes to your electricity needs and can save you a lot of money in the long run.

What Are 3 Important Uses Of Solar Panels?

The three most important uses of solar panels are;
1. Solar electricity. This can be used to power almost any appliance in your home, including TVs, computers, and fridges.
2. Lighting. In addition to the use of low-power, LED lightbulbs, solar panels can provide an efficient, low-cost, and environmentally friendly way to provide lighting to homes. 
3. Portable solar. In our modern, always-connected lives, our phones, tablets, and computers are almost always with us, and all run on batteries. Portable PV chargers can help keep our batteries topped up no matter where we are, as long as there is some sun to charge them.

Do solar panels give you free electricity?

Once the cost of the array is paid in full, the energy it produces is free. There are ongoing maintenance costs, too, such as annual panel cleaning, etc. 

How much will my electric bill be with solar panels?

Suppose your solar array includes a solar battery backup system, and it is large enough to fully cover your energy usage per day. In that case, your monthly electric bill will be next to zero dollars, even with a grid-tied system. 

If your solar array does not include a solar battery backup system, then at night, your house or business will use grid electricity. That cost will vary but expect to pay from 1/3-2/3 of your average electric bill, and that cost will fluctuate seasonally. 

Do you save money with solar panels?

The simple answer is, Yes, you save money with solar panels. There is an initial upfront cost, but since solar panels are warrantied for 25 years, you will save money over time. You will also begin to see monthly savings in energy bills, but there are other ways that solar panels pay you back. Those include:
1. Adding value to your home or commercial building 
2. Monthly decreases in energy costs
3. The ability to add more energy appliances without increased monthly costs
4. The potential for tax credits for going solar

Can solar panels power a house 24-7?

Most definitely! Solar panels can certainly power a house 24-7, with the addition of a high-quality inverter and a suitable battery bank, of course. To power, a house under normal usage will require a massive solar array, though, and there will be a very expensive initial financial outlay.

Do I need to tell my energy supplier I have solar panels?

This depends on where you live, but in most cases, it’s not necessary to inform your energy supplier that you have solar panels. That said, you may be producing excess power with your solar system, in which case you may be able to sell that excess power back to energy companies.

In this case, you’ll naturally need to be in contact with them. 

What Are Solar Cells Known as and Why?

Solar cells are also called photovoltaic (PV) cells. They are called so because the term ‘photovoltaic’ literally means light i.e. photo and electricity i.e. voltaic.

These cells generate electricity through the photovoltaic effect. This effect basically causes the generation of free electrons from the semiconducting silicon material of the solar panel when sunlight hits its surface.

What Type of Solar Panels Are Most Efficient and Why?

There are currently three types of solar panels available in the market that are:
1. Monocrystalline
2. Polycrystalline
3. Thin-filmed

Among these, monocrystalline solar panels are known to be the most efficient among all others.

Does heat enter your home through the roof?

Absolutely. Heat enters your home through your roof, and on a hot day your attic can get up to 150 degrees Fahrenheit or more. Through conduction, heat from the sun warms your roof which then warms your attic and the rest of your home.

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