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- Solar energy disadvantage 1 – Dependence on the weather
- Disadvantage of solar energy #2 – Solar panels don’t work at night
- Diasadvantage of solar energy #3 – Environmental concerns
- Other Questions Frequently Asked:
The Pros and Cons of Solar Energy
Just a few years ago one of the main disadvantages of solar energy was cost. This is no longer the case.
The cost of producing solar panels has fallen tenfold in as many years and financial incentives make it very attractive for the homeowner.
However, solar energy does still have significant disadvantages which we should be aware of.
The 2 main disadvantages of solar energy are dependence on weather conditions and the inability to store electricity. Solar energy output depends mostly on direct sunlight. A cloudy day can reduce electricity generation by more than 80%. Solar panels generate no power at night and so batteries are needed for 24 hour supply.
Video – Advantages and 2 main disadvantages of solar energy
Solar energy disadvantage 1 – Dependence on the weather
I think solar energy is a miracle that should not be understated. It’s clean, there are no moving parts and it can help to clean up our planet.
However, solar panels have a massive disadvantage – if the sun doesn’t shine, no electricity is generated! The amount of power generated is hugely dependent on the strength of the sun’s rays. If solar panels are shaded by passing clouds, power output will drop.
How efficient are solar panels?
Most commercial solar panels are between 18% to 20% efficient. Some manufacturers (such as Dokio) boast up to 25% efficiency, but this is still quite low.
It means that for every 1000 watts of the sun’s energy falling onto the panel’s surface, we get about 200 watts of electrical power. The solar cell conversion process is not that efficient.
Compare that with solar water heating, which transfers the sun’s energy to water with up to 75% efficiency. The difference is that it is a thermal transfer and not a conversion process.
The effect of irradiance and location on solar energy output
Irradiance is a direct measure of the sun’s energy falling onto solar panels and varies according to location. It’s measured in kilowatt-hour per square meter per day (kWh/m2/day or year) which is also known as peak-sun-hours.
Solar installers use this value to estimate how much energy a solar panel will produce. The average irradiance for the USA is 4 peak-sun-hours. For a 100 watt solar panel:
Energy generated by 100 watts solar = 100 watts x 4 peak-sun-hours = 400 watt-hours.
Some locations have high irradiance, like Nevada, and others have low irradiance, like Alaska. Alaska’s low irradiance is a big disadvantage for people considering a solar energy installation.
Poor weather in the form of clouds has the same effect as low irradiance as the sun’s energy is blocked.
Effect of cloud cover on solar panels
All solar power systems are subject to a variety of losses which reduce the power output of solar panels.
Some losses we can impact, such as cleaning, but other we have to live with. One of these losses we can’t improve is the effect of bad weather and cloud cover.
The iofographic below shows that shading losses due to poor weather can be up to 7%. For an average size solar system of 6kW this represents 420 watts, almost half a kilowatt.
Without suitable protection using suitable electronics, a 60 cell solar panel can lose up to 75% of its power output if just one cell is completely covered!
In real-life situations all of a panel’s cells are subject to reduced irradiance due to various types of cloud cover. It can be a major disadvantage.
Infographic – Typical solar PV losses in a home installation
What kind of protection prevention is used against shading?
In the early days of home solar power system design an individual inverter was used to convert the DC generated by solar panels into the AC needed by home appliances.
This topology was efficient enough when all of the solar panels were irradiated in full sunshine.
However, if even one of the solar panels became covered, the output of the whole system would be reduced, sometimes dramatically.
The modern solution is to install micro-inverters at the panel level, or a small groups of panels. This has the effect of limiting power reduction to a small part of the solar power system
Disadvantage of solar energy #2 – Solar panels don’t work at night
Although research into solar panels that work at night is ongoing, they don’t yet exist in any viable form.
Solar panels work best in full sunshine during the four or five hours around mid-day. Power output reduces rapidly in the early morning and late evening (see power output curve below.)
If power is required at night, for an off-grid solar power system for example, then batteries will be required.
The additional cost of batteries to a solar installation can be up to 30% of the overall cost, which is a major disadvantage.
Even for a grid-tie system it’s not ideal, as during the night power is taken from the grid. Although the home-owner is credited for solar over-production, a few cloudy days could severely reduce the savings associated with on grid solar.
One solution is to install home energy storage batteries, even if connected to the grid. In this way they will always be topped up and ready to supply power at night or during an outage.
Diasadvantage of solar energy #3 – Environmental concerns
The third disadvantage of solar power is very important and shouldn’t be minimized – although they are very clean in operation, solar panels are potential pollutants.
Solar panel manufactures give warranties between 25 to 30 years, guaranteeing output up to 85% to 90% after that time. Panels may continue to generate power for up to 50 years.
It seesm reasonable to suppose that homeowners will opt to replace solar panels soon after the guarantee period, rather than experience declining output levels, particularly if prices keep coming down.
Hundreds of thousands, if not millions, of solar panels are being installed right now and these will be scrapped in 25 years. Where are they going to go?
Do solar panels have toxic chemicals?
The main active component of a solar cell is silicon – it’s basically a flat semi-conductor. Almost everything that goes into a panel’s construction is rich in heavy metals which are toxic to various degrees.
The question is how to deal with them when they are no longer needed?
Much research is being carried out with a view to recycling them back into usable panels but there are major problems. At the current time it seems as though the easiest (and worst) solution will be to bury them in landfills.
Over time the heavy metals will leach out into the environment so this is not a good long-term solution.
Complete recycling is possible but the issue is cost. It costs 3 times more to recyle solar panels than to simply bury them. The story is ongoing …
Other Questions Frequently Asked:
Do you really save money with solar panels?
Solar panels really do save money, and also make money as they can increase the value of your home.
The calculation below shows the savings and payback period for a solar panels installation in Houston, Texas:
- City: Houston, Texas
- Average size of system: 5kW
- Cost of solar = $13700 – 22% federal tax credit = $10686
- Irradiancein Houston, Tx = 1552
- Electricity produced = 1552 x 5kw = 7760 kWhrs
- Cost of electricity = 10.98 cents/kWh
- Amount saving per year = solar production x electricity cost = 7760 x 10.98 = $852
- Time to payback = cost of solar system / yearly savings = 10686/852 = 12.5 years
In addition, Zillow found that a solar installation adds around 4% to the value of the average American home.
What are 2/3 disadvantages of solar energy?
The top 3 disadvantages of solar energy are:
- Can be severely affected by the weather (clouds and rain reduces irradiance)
- Cannot generate power at night (batteries are required for off-grid systems)
- Potentially toxic and difficult to recycle (heavy metals can leach from landfills)
How long do solar panels last?
Manufacturer’s warranties vary from 25 to 30 years, with a guarantee of 90% production after that period.
Solar panels can continue to generate power for up to 50 years, with reducing output of 0.8% per year.
Do solar panels need servicing?
The actual panels don’t need servicing unless the output reduces. In that case, simple tests can be carried out to see which panel is at fault.
The only regular maintenance recommended is a twice-yearly cleaning to remove any dust and debris. Dust and dirt can result in a 2% loss in output power.
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