Ever wondered where the batteries on some calculators are supposed to be inserted. Well chances are that the calculator you are holding doesn’t need to replace its batteries because it runs with the help of its own tiny photovoltaic solar panel.

solar cell calculator

Photo: Public Domain Marina Shemesh

Yes that’s right if you look closely you will find a strip of shiny black squares, that’s the calculators solar cells. These will make the calculator run for as long as light is hitting the panels and it doesn’t need much light either. A small light bulb or a window across the room will give the solar cells enough light to generate power to run the calculator.  You can simply test this out by covering the solar cells with your finger, the calculator will almost instantly shut down. When you remove your finger and again let the light hit the small solar cells the calculator will star working again like magic. Only it is not magic it’s a photovoltaic  event.



Photovoltaic or PV comes from the word photo which means light and voltaic which translates to electricity. So basically light electricity or as it is more often called today, solar power.

Solar panels

The same solar cells that you find in the calculator are installed in some of the large photovoltaic solar panels atop the roofs of many homes today. The only difference is that the bigger roof modules consist of more and bigger solar cells then the ones in the calculator. But the main thing about them remains the same, they will all take light and convert it into electricity.

Solar array

If you take a group of photovoltaic solar panels and connect them together you will get something called a solar array. A solar array can be any number of sun modules everything from the 3 panels on your neighbors roof to the large fields with thousands of PV panels connected into multiple solar arrays at solar power plants. Power plants just like mount signal solar that is generating 265.7 mw in California USA

photovoltaic solar panels

An array of solar panels basking in the sunligt
Photo: Public Domain Vera Kratochvil


How photovoltaic solar panels power your house

Powering your house with solar power is actually not a complex thing. First and foremost your solar system convert sunlight into electricity. Then the electricity is led into your home to power appliances like your TV or fridge. It’s as simple as that.

It’s what we do when there isn’t any sun shining to give us electricity that makes it a bit more difficult. Basically you can chose from taking your power from batteries or to draw power from the grid during sun scarce times. What you chose decides if your solar system will be an off grid or on grid one and that in turn will greatly decide what equipment you will need and the price for the whole shebang.

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An off grid solar system uses batteries to store unused electricity. And you will need

  • Solar panels
  • A solar regulator that regulates the amount of power sent to the batteries
  • An inverter to be able to power non 12v appliances
  • Lots of batteries.


An on grid solar system feeds electricity back into the mains grid and consists of

  • Solar panels
  • A dc-ac inverter
  • A switch board to feed electricity either to/from grid or to/from solar
  • A special electrical meter that can go both backwards and forwards


How solar panels work

Today photovoltaic solar panels are most often made out of a shiny metal called silicon, silicone is a semiconductor and it is the same stuff that the chips in your computer are made of as well. The solar cell transforms light into electric energy by a photovoltaic process. It works like this:

A beam of light or a photon hits the solar panel, the light can then behave i 3 different ways either it is reflected away by the surface of the solar cell, or it can pass through the solar cell without getting converted into electricity or in the third case it can be absorbed into the solar cell. In the scenario where the light is transferred into the silicon it means that the energy that the light beam consist of will be transformed into electrical energy that you will be able to use to power your household appliances with.

First the light wave or photon directly hits an electron knocking it away from its orbit around the core of a silicone atom. The electron is now free and can roam about

The photovoltaic solar cell is build in a way that gives them electric fields charged either in a positive or negative manner. Just like a magnet on your refrigerator has a positive and a negative side. Because electrons always are charged negative they will be pulled towards the positive charge of the panel. When you have lots of electrons getting pulled towards the same direction you have a current of electrons witch more exactly is what defines an electrical current.

If we dam up the path for the electrons and force them to run through the power outlets of our home before reaching their destination on the positive side of the solar panel, we can for example force the electrons to run a fridge or a TV. This is done by attaching wires to the top and bottom of the solar cells and drawing the wires to our house.

Photovoltaic electrical facts


How strong the “magnetic” fields is decides how many volts that particular solar cell is able to output. Of course we can increase the voltage  by connecting a number of solar cells together in a series. This factum with a little help of an inverter would be why a solar panel containing multiple solar cells can power your home with the standard of 220-240 volts. A solar cell is normally able to output 0,5 volts no matter if it is big or small and most of the time a solar panel will have enough solar cells so it will output up to 12 or 24 volts, which in turn also is the voltage of most of the large batteries built today.


The size of the solar cell on the other hand decides another important thing and that is how many amperes the solar cell will produce. The ampere measures how many electrons that are passing by in your electrical wire per second. The bigger the solar cell the more electrons will get knocked out of there orbits and the more amps the cell will produce. This is why a big solar cell can output a lot of amps while a small one like the one on a calculator will only be able to produce a tiny amount of amperes.  You can connect your cells in parallel to make their area larger and that way increase the ampere


Most of the time you will see a photovoltaic solar panels marked with a certain number of watts. This number is the maximum number of watts per hour that single panel cold produce when the optimal amount of sun hits it. Watts are calculated amps*volts=watts. So by increasing either the voltage or the amperes you will increase the total watts of your system. This basically means that to get more electricity you will have to either increase the number, or the size of solar cells. Both alternatives result in the need for a larger roof area, sense it will call for the need of either bigger solar panels or simply more of them.

The wattage of photovoltaic panels vary very much and can range from small 5w hobby panels to exceptionally powerful ones at 315w. A normal roof solar panel though, lies in the scope of 150w to 240w/ piece. Meaning that if you have a PV panel marked 200w you will be get 200w per hour from it during the time that the sun shines at it with optimal power. This would result in you being able to run a vacuum cleaner at the lowest setting “200w” or a desktop computer during a couple of light hours of a day

From this calculation you understand that much more than one solar panel is needed if you would like to provide yourself and your family with the electric power that you need. But how many panels will you need?


How many photovoltaic solar panels do I need to power a home?

How many solar panels you will need to power your house is dependent on many factors. How much power you consume in the first place is an important one. To find that out you can either look at your electrical bill or make a calculation based on how much power your household appliances use.

The other thing you will need to know is how much sun you usually get. A solar panel will only work when it’s being hit by the rays of the sun in some way. Meaning that in a sunnier climate closer to the equator your panels will catch more sun and produce more power, and in the south or north parts of the world photovoltatics will not be as effective.

Depending on your location you will get between 3-8 great sun hours a day. 3 hours is for Canada northern Europe, UK and Russia. For USA, Australia, south America, Africa, Southern Europe and India the peak sun hours will lay in the 6-8hours/day range .

Lets make an example:

So let’s say for example you have a small energy efficient  home for 1-2 persons that runs on 2 000kwh/year. This will mean that you use up approximately 5500w each day

2000kwh/year= 5479wh/day = 228w/h

For simplicity’s sake say you would want to buy some 200w panels that would produce all your needed power in just 1 hour’s time. The below calculation shows that you would need 27pcs of 200w photovoltaic solar panels to produce 5479w in 1 hour

5479w/200wpanels=27panels in 1 hour

Luckily the sun will shine more than 1 hour in average during a day. Let’s say you live in a sunshine deficient area like UK where the sun fully shines only 3 hours in a day. This would mean you will have to put up9pcs 200w panels to cover your needs. If on the other hand you live in Australia only 3,4 200w photovoltaic panels would suffice.

27 panels/3 sun hours=9 needed panels
27 panels /8 sun hours =3,4 needed panels


how much roof space do photovoltaic solar panels need

Photo: Public Domain Mark Yang

How much roof space will I need?

Using above panel would mean that in UK you one would need to cover 144ft²(13m²) with photovoltaics though only 55ft² (5m²) in Australia.If we continue with the above example i have found that one usual 200w solar panel covers approximately16ft² (1.5m²) of roof space. This size is different depending on different types of PV panels. The cheaper variants like thin film solar panels are generally much bigger than the more effective monocrystalline ones. But let’s count on an average polycrystalline solar panel for simplicity.

16ft²*9 panels= 144ft² (13m²)
16ft²*3,4 panels= 55ft² (5m²)


Can I install solar power even if I live in less sunny area?

solar panels in cloudy foggy cold latitudes

Photo: Public Domain George Hodan

A photovoltaic solar panel will absolutely work in a cloudier and cooler climate. The cold makes no difference and the clouds will only withhold the rays of the sun a bit. Meaning that the affected area will have less peak sun hours during a year. But as you have seen on the above calculation this only results in you needing to add more solar panels to cover your energy need.

Fortunately PV cells keep on producing power even during a fog. Actually the drawbacks of panels installed in a foggy area vs. A not so foggy area are only 1%.

The photovoltaic systems of today have become both much more effective and vastly cheaper than the ones from only a couple of years back. The result of this being that going solar will pay off even if you live in the more northern parts of the world. It will just take a little longer before you break even that’s all.

An investment in sun generated power will generally pay itself off in between 2-7 years time. Everything after that is just free electricity. and we haven’t even begun to count on the feed in tariffs that allows citizens to sell the excessive power back into the grid for profit.

What needs to be added though is that your solar panel cannot be completely or partly shaded by an object like for example a tree or another house. Where’s a completely shaded panel will perform very poorly and a partly shaded panel will most likely not work at all.

Installing the PV panels

The best way to install solar panels in your home is to find a professional photovoltaic power installer and let them do the work for you. A solar company will do all the hard bits like measuring your house energy potential and calculating what system you and your family will benefit from the most. They will also come and install everything for you. Having seen all the gear, big machines and people it takes to install a solar powered system on a roof. I must say that the extra cost for not needing to do it yourself is definitely worth it. Plus you will get guaranties and automatically be able to hook your system into the national grid. The power companies won’t generally let you sell your power to them if your solar system is not put up by a professional.

If you despite that want to do it yourself, there is every chance for you to succeed just as well as any firm would. It will only take some hard work and that you have studied up so you really know what you are doing. Just remember that by installing it on your own you are limiting yourself to an off grid solar system.


How much solar panels cost?

The final price of your photovoltaic solar panels is dependent on many things. The biggest factor on the price is how big your system is going to be. More PV panels will naturally cost more money. The second factor is if you chose to install an off grid solar system or a gird tied one. The necessary cost for batteries when going off grid will greatly surpass the cost for the solar panels themselves. But if you chose the cheapest form of solar energy available you can have a  1kw fully operational gird tied solar system for as little as 3000$. But for most households a 1kw system will be far too small and is probably best fitted at a small vacation cottage. Solar panels with the capacity of 5kw for the price laying about 10 000$ (year 2013)are much more reasonable.

This will give you panels and peripheral equipment capable of producing 5000w of electrical current every full hour the sun shines on them. Even if you live in a not so sunny part of the world where the sun only shines at full power during 3 hours a day, like in the United Kingdom, you would get 5500kwh a year. This is what an average villa family of 3-5 people consumes around the world except the us.


In the states an average household consumes about the double amount of electricity than in for example England totaling about 11 000kwh/ year. On the other hand the sun also shines for double the amount of hours resulting in the 5kw solar system for 10 000$ still as appropriate for an American family.

Of course there are those that pay way more for their solar power. I have heard of people that want to run their air-conditioning or heating on solar, ending up spending as much as 50 000$ on their photovoltaic solar panels initial costs.


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6 Responses to Photovoltaic Solar Panels

  1. Danilex says:

    Thinking of installing solar panels in my summer home, tnx for all the great info

  2. Angie star says:

    Haha gotta love that sexist picture of the photovoltaic installer man. He can come home to me and put up anything he wants GRRRR :-P

  3. Morgen says:

    I live in Norway do you think that installing solar panels would be profitable for me as well?

    • Photovoltaic Solar Panels .net says:

      Absolutely! As far as we know Photovoltaic panels will always pay themselves back. How long it will take will depend on where in Norway you live. The further up the less sun you have.

  4. Oteni says:

    Your article is very very educative, thanks. What equipment do i need to install a 200w panel off-grid in West Africa?

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