How Do Solar Panels Work? FAQ About Solar Panels Operation

Solar panels can be used in and around the home, garden and outdoors. The big questions is: Which Solar Panels Are Best For Home, RV or Camping Use? A great place to start is to have some basic understanding of what a solar panel is, how it works and how much power you can expect for different sizes and solar panel types.

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Solar Panels: How Do They Work?

You might know that transistors, diodes and a whole range of other specialized semi-conductors are made from silicon. It may surprise you to learn that those big flat solar panels are basically the same thing.

Two slices of silicon are fixed together, but one of them has been doped with phosphorous, which changes the electric characteristics, allowing electrons to readily flow from one side of the cell junction to the other. This is what an electric current is – movement of electrons.

When a photon of light hits the cell it dislodges an electron which jumps over to the other side of the cell.

A panels can have any number of solar cells from 36 to 144, but normally domestic installations use panels with either 60 or 72. The cells are created by taking thin slices of the silicon crystal nugget or ingot, attaching highly conductive strips of metal to collect the voltage, and connecting them together on a flat mount.

Silicon is quite reflective and so the finished solar panel is coated with an anti-reflective treatment and sealed against the environment before use. Different types of solar panels have different efficiencies, that is, they make varying amounts of power for the same insolation.

Note: Insolation is the amount of sunlight energy falling on a certain area. The standard definition for solar panel ratings is 1000 watt/m2.

Here’s a list of things you should know about domestic solar panels.

Which Is Better Monocrystalline or Polycrystalline Solar Panels?

There are two main types of construction – monocrystalline and polycrystalline. Overall efficiency of each type is improving every year while the cost is being aggressively pushed down.

Monocrystalline panels have the better efficiency at around 20%. The better quality products can have efficiencies up to 23%, but of course you pay more. Polycrystalline panels come in at 15% or so – it varies by maker’s quality. It’s worth mentioning that the quality aspect of solar energy systems is very important, both from the point of view of output and longevity.

Polycrystalline are cheaper, so if you have plenty of space, it may be more cost-effective to buy a few more panels. It all depends on the size of your installation and the operating conditions.

Factors Affecting Solar Panel Efficiency Over Time

These factors affect solar panel power output and how long they will continue to operate:

1. Quality – environmental degradation can affect watts output and life of service
2. Insolation – how much of the sun’s energy falling on your roof directly relates to power production
3. Maintenance – panels should be regularly wiped. Cleaning dust off can result in 5% in wattage gains!
4. Shading – care should be given to ensure solar panels are not shaded, but overgrown trees, for example.
5. Orientation – fixed installations perform best with an angle of 60 degrees (see solar tracking below.)

Tracking solar panels vs fixed

Solar tracking efficiency gain can be considerable, depending upon your latitude and insolation values. It’s well-documented that solar installations that follow the sun’s passage across the sky can produce up to 65% more power (watts) in high summer and 40% more energy (kWh) annually.

You can see from the chart below that in a fixed installation produce the most electricity during the middle of the day exactly when our demand is low! The sun is high and most people are having lunch – it figures. The amount of watts generated falls off rapidly in the mornings and evenings, when the sun’s angle is acute in relation to the surface of the panels. This angle is crucial and explains why sun tracking can be a great idea.

The bottom curve indicates when we use most electrical energy. There’s a spike in demand at breakfast and in the evenings. Paradoxically, these are the times when solar installations produce very little power.

Courtesy LG

Inevitably, cost-effectiveness is a compromise between energy savings vs installation cost and you would only find this out by calculating the cost of your proposed system.

The best systems  align the solar panel arrays in two axes, but even a single-axis setup can bring considerable gains. The choice of single or dual axis solar tracking systems also depends on your geographical location.

The blues line on the graph below shows the distribution for a fixed solar system and the red for a dual-axis sun tracking installation. A single-axis system tracks the sun horizontally from East to West, while a dual-axis arrangement also tracks vertically North to South.

Chart showing the difference in fixed and dual-axis tracking solar panel arrays

How Can Solar Energy Be Made More Efficient

Improving solar panel efficiency beyond their design characteristics has been and still is one of the Holy Grail’s of photovoltaic electricity production. After all, compared to a solar hot water panel’s efficiency of 70%, PV isn’t even close at approximately 20%.

Many people have tried to boost the output of PV solar panels in various ways, mostly by increasing the intensity of sunlight falling on the active surfaces.

Limited success has been enjoyed with Fresnel lenses. This is basically a flat plate with conical magnifiers built in. In theory, if a 2 meter square Fresnel lens is positioned over a 1 meter square panel, then its output in watts should go up. It does give it a boost of between 10% and 30%.

Most Efficient Solar Panels By Manufacturer (2020)

Mirrors are traditionally used and efficiency gains of up to 50% have been claimed, but both methods have a serious disadvantage – heat! Manufacturer’s ratings and warranties are assessed at 25 degrees C.

A panel’s output drops progressively the hotter it gets. Paradoxically, the device fitted to get more watts out of the panels is causing power loss and eventual degradation of the cell structures, probably voiding warranties of supplier and installer.

One result of this phenomenon was the development of hybrid water and PV panels. The theory is that if water is used to cool the solar cells, that water can be used in a domestic hot water system. It isn’t a large-scale commercial success and is probably not worth pursuing.

How Long Do Solar Panels Last On Average?

The best quality panels last 25 to 30 years, but that’s not to say they are useless at the end of that time. Generally, manufacturer’s warranties specify 80% capacity at the end of their life.

It’s traditionally been accepted in the industry that solar panel production capacity reduces at a rate of 1% per annum. You can expect to get about 75% of the new installation’s power production after 30 years or so.

However, recent studies show that the rate of degradation can be as low as 0.5% per year, which is of course much better and good news for the homeowner. But why the big difference? The answer is Quality.

Solar panels sit on your roof 24/7 and endure everything that the elements can throw at them. The best quality panels are more able to resist environmental challenges and big fluctuations in operating temperatures that tend to degrade connections and pale cover transparency.

Which Are The Best Solar Panels For Home Use?

It’s crucial that you buy the best quality you can afford. it may be tempting to cut costs in the short term, but it’s the long term gains that are important in terms of energy savings. The companies below can be relied upon to supply the best solar panels for home use.

Top Solar Panel Manufacturers In The World

How Much Are Solar Panels For The Home?

You can expect to pay around $3 to $3.50 per watt installed in 2021, and the average installation size is 4000 kWh. In the States solar tax credits can offset the cost.

The individual panels average about 1.7 square meters in area and are mostly oblong rather than square-shaped. Typical size is 1700 mm x 1000 mm (67 inches x 39 inches) and the outpower in Watts (W) between 250W and 360W. A good rule of thumb for purchasing panels for DIY use is to expect to pay 1.5 cents/watt.

Which Solar Panels Are Best For Home Use?

Without a doubt it’s always advisable to buy high-quality panels from the best solar panel manufacturers. Any of the companies mentioned in the tables in this post are known for the best quality.

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You can easily do your own research using the following search queries:

• Which solar panels do homeowners purchase the most?
• Solar panels homeowner reviews – make a small survey of which panels people are satisfied with
• What are the most efficient panels for small areas?
• The best solar panel installers for small budgets
• What solar panels are built to blend in with your building?
• Solar panel deals, blowout deals, solar installation promotions – you never know!
• How many solar panels do I need for my house? (see calculator below in this post)

The best solar panels for the home depend to some extent on your specific requirements, such as energy consumption and what percentage of that consumption you want to replace with solar.

Understand Solar – Installer’s Directory

Tesla Solar Panels For The Home

For several year’s the idea of a complete roof made of solar cells was proposed by Tesla and it never seemed to be happening. In 2020, there have been several installations and it’s yet to be seen if this idea is going to be viable or not.

Tesla market the product as complete solar power kits for homes and designated installers take care of everything from ripping off the old roof tiles to applying for permits to hook your system up to the electricity grid.

Each tile of the Tesla ‘glass tile roof’ measures 1140mm x 430mm and simply replaces a conventional roof – a great idea if your roof is close to the end of it’s life. A tesla glass roof PV system will cost 2 to 2.5 times more than a new conventional roof, even after federal rebates.

Calculations indicate that the overall efficiency is around 10%, compare to 18% using conventional solar panels. However, the important thing to look at is the cost/payback numbers. It’s a cool thing for many homeowners to have an electric roof that looks much like a normal roof, without panels sticking up spoiling the profile.

Are tesla solar roof tiles worth it?

Early Tesla solar roof reviews suggest that homeowners are generally happy with their choice, but it’s early days. For me, I don’t mind the look of conventional solar panels. Yes, they stick up a little and don’t look like the rest of the roof, but they are more efficient and cheaper.

Besides that, I suspect a time is coming when aesthetic considerations are far outweighed by the need to be independent of utilities as much as possible.

How many solar panels do I need?

How big are residential solar panels?

The table below gives you some idea of the dimensions of typical solar panels used at home. It’s worth noting that the thickness value is for the panel itself. They are normally mounted a couple of inches away from the roof to allow for wiring to pass and air to circulate.

Solar Panel Size Chart (Typical Solar Panel Sizes and Wattage)

The number of solar panels needed depends on your requirements, how much energy you use each day and such factors as the insolation level in your area. Do you want to generate enough electricity to cover all your bills? Let’s assume you would like to eliminate your bill – sounds good.

How Much Energy Will My Solar Panels Produce?

Most homes in the U.S. use on average 900 kWh/month, which translates into 9 kW power draw for 100 hours, or 4.4 kW for 200 hours, and so on. This figure can be found on your utility bill.

• Divide you annual kWh reading by 12 to get a monthly value
• Divide the monthly kWh by 30.33 to give you a rough idea of your daily energy requirements.
• Divide the daily figure by 1 kWh to give a rough estimate of solar panel numbers needed

In the case above the daily consumption would be:

900/30.33 = 29.67 kWh/day

Assuming that a solar panel produces 1 kWh of electricity per day, you would need 30 panels to cover all your energy needs, but it’s best to 10% to 15% more to account for possible additions in the future, such as pool heating or house extensions, for example.

The recommended size of the above installation would be 4500 watts of solar capacity, but 5200 watts would cover future expansion., at an estimated mid-range installation cost of approximately $16000.

Why Is Solar So Expensive To Install?

The cost of installing solar can be broken down into the following categories:

• Hardware – solar panels, inverters and other equipment – 25%
• Marketing has to be taken into consideration by installers accounting for 20%
• Overhead – these are costs incurred by an installer, like insurance, office space,etc. – 20%
• Labor is usually at a high premium as the installers employ technically qualified people – 10%
• Permits other paperwork – the inevitable bureaucratic stuff! – 25%

So a whopping 50% of the cost comes from the installer’s costs external to your installation. The enthusiastic do-it-yourself guy could easily install solar panels if he had the technical know-how. Thankfully, this is easily come by on the internet.

Make a quick calculation based on your own home. The calculator below will give you some idea of the number of 300 watt panels you would need for your home, based on your energy consumption – take the annual reading from last year’s utility bill.

The average energy consumption of an American home is approximately 11000 kWh/year, or 916 kWh/month.

It also assumes an average insolation value in the United States and a fixed roof installation (reduce the number of panels by 40% if you plan to install a sun tracking system.)

How many solar panels do I need to power my house? – Calculator

What Else Is Needed For A Solar Power System?

• Solar panels – that one was pretty obvious!
• Solar inverter – these are essential items for converting dc to ac voltage
• Net metering – a piece of equipment designed to measure electricity flow between you and the utility company
• Solar performance monitoring – every engineering system needs a means of measuring its efficiency
• Solar storage – batteries may be a good idea if outages are common in your area

If considering an off-grid solar system, then a substantial solar battery bank would be required based on your annual energy consumption.

Other Ways To Use Solar Energy In The Home

Is Solar Pool Heating Worth It?

Solar water heaters are widely employed to provide heat for swimming pools, and in certain circumstances it can be cost-effective. It depends on your location and how passionate you are about swimming. Maintenance of solar water heaters using heat exchange panels is very low.

Solar water heating is an environmental friendly system that compares very favorably with other heating methods.

• It’s possible to get substantial heating even in the winter season
• The energy is free source, so it’s definitely cost-effective long term
• There are no emissions so not harmful for the environment
• Low maintenance
• They can be installed at both ground and roof

Direct solar heating comes in several forms, active and passive. Passive is when a part of the structure of a building or pool exchanges heat from the sun’s rays while active systems use heat exchangers.

Passive solar pool heaters include transparent covers that roll over the pool, black floating mats that simply lay on the surface, thereby stopping the heat escaping and also passing on heat energy absorbed from the sun.

Active solar heaters normally involve the installation of panels or coils of pipes to heat a separate water circuit which then exchanges heat with the pool water. Some systems heat the pool water directly by pumping it around a solar panel mounted at an angle in the sun.

When you consider solar pool heating systems have a 25 to 30 years life span and zero running costs, it makes complete sense. You’ll find a great selection of heaters offered by SolarDirect online.

Solar panel kits for sheds

Many suppliers offer complete kits of various sizes, from 100 watts upwards. If you have a garden shed situated away from the house, it could be well-worth the expense, It’s fair to say that some of these DIY solar kits can be expensive but there are considerable advantages to the kit approach to DIY.

The main benefit is that all of the various components are sized according to the kit function, so your technical knowledge doesn’t come into it. One thing to consider is solar battery storage, which may not be an issue if you mostly use the shed during the day.

In my opinion, a small solar installation is the perfect way to cut your teeth on do-it-yourself in the renewable energy field. You’ll save hundreds of dollars by taking the time to size the components and wire it together yourself.

Solar Innovation Infographic, courtesy of the National Renewable Energy Laboratory