By reviewing world energy consumption data, we find out that worldwide energy usage has risen from 102,300 TWh (terawatthour) in the year 1990 to 142,300 TWh in 2008, which is an overall increase of 39.1 percent in just 18 years. That is a compound growth rate of 1.85% per year. If we continue with the same energy usage trend in the future, we can forecast that by year 2030, we will need approximately 212,970 TWh of energy in order to satisfy world energy needs. ^{*1}
In the Land Art Generator ^{*2}, the calculated relative difference was around 7% less (678 quadrillion Btu or 199,721 TWh) than what is calculated here, so we decided to redo the calculation.
Original photo source: "Solar panels on the library's roof" by Marshalltown Public Library
We calculated that the energy required for the entire year in 2030 will be 212,970 TWh or about 727 quadrillion Btu (British thermal units) where 1Btu = 0.293071 Wh (watt hours). ^{*3}
Solar panels in the current state can generate up to 0.2kW of electricity per square meter, when all requirements are fulfilled.
If we take one year, or 365 days, out of which only 70% will be sunny days and during which we can generate electricity only 8 hours each day, it will give us a modest 2044 sunny hours per year. ^{*4}
When we multiply the number of sunny hours per year by a solar panel’s maximum power of 0.2kW per square meter (of solar panel) — it will give us roughly an output of 400kWh per square meter of the surface of the photovoltaic panel per year.
If we divide 212,970 TWh with 400kWh we will get a surface area of 532,425,000,000 square meters, which is equal to 532,425 square kilometers or 205,570 square miles.
Picture a square with sides 730 km long that can roughly fit over the area of Spain and Portugal.
Consider that the Sahara Desert, which is mainly uninhabited, has an area that is 18 times (9,000,000 square kilometers) more than what is needed to power the entire world.
Considering that the total area under the subtropical desert is around 15,500,000 square kilometers ^{*5}, we can safely conclude that, even without considering ocean surfaces as possible solutions, we have more than enough space to generate energy for all our needs, without having a negative impact on our habitats or the land we use for agriculture.
Now, what about money? How much would such an investment cost?
Photovoltaic panel, SW 285 Mono Black with a 25 year linear performance guarantee, is priced around US$350 ^{*6}. The SW 285 size is 1.67 square meters; which translates into US$210 per square meter. But, solar panels cannot operate on their own and usually need a battery pack, inverters and cables. So, a real price for a small system will end up being around US$370 per square meter.
If we multiply 532,425,000,000 m2 with US$370 we will get US$196,997,250,000,000 or 197 trillion US dollars.
That is a huge amount of money. Is it possible to achieve a project of such magnitude?
According to the World Bank, the 2013 nominal GWP (Gross World Product) was approximately 75.59 trillion US dollars.
In order to find an appropriate way to fund something like this, we will consider the entire world population that has a daily income of $10 or more. ^{*7}
According to the Pew Research Center data, 13% of people worldwide live on an income of 10 to 20 US$ daily, 9% have upper middle income earnings between 20 and 50 US$ daily and 7% earn more than $50 a day.
If every person from the first group would leave aside $1 per day, each member of the group could buy one square meter of solar panels after one year. Each member of the second group could put aside $3 a day without experiencing significant strain on his budget, and each member of the highest paid group cold put aside $8 a day without being significantly affected.
Original photo source: "Installing solar panels" by Oregon Department of Transportation
That would mean the following:
World  %  population  investment  days  

7,125,000,000  $10  20 per day  13  926,250,000  $1.00  365  338,081,250,000 
$20  50 per day  9  641,250,000  $3.00  365  702,168,750,000  
> $50 per day  7  498,750,000  $8.00  365  1,456,350,000,000 
The total sum would be $2,496,600,000,000 per year, divided by $370 for a square meter of panels, which equates to 6,747,567,568 square meters of solar panels each year.
If the companies where they work would match each dollar with another dollar as a form of energy dividend, similar to today’s pension schemes, the total number of panels would be equal to 13,495,135,135 square meters.
According to what was calculated previously, if we divide the total solar panel surface necessary to satisfy all our energy needs by the above maximum solar panel number we can afford per year without significant strain, 532,425,000,000 / 13,495,135,135, we could achieve the goal of replacing all energy sources with solar in a bit less than 40 years.
Given our deadline of the year 2030, we only have 14 years to reach the goal we have set. So the question is:
Is the goal still achievable?
The above was a pessimistic calculation and here are few things we have not included:
First and foremost, the number of sunny days we used to calculate the necessary area was bit above 2000, which can be found anywhere on the planet, but it is significantly lower than what can be found in deserts. In a large part of the Saharan Desert, the number of sunny hours per year is 3600–4000 and, in some parts, that number can even exceed 4000 sunny hours per year. Just factoring in those numbers, would slash our calculation to half, giving us half of the surface area and half of the time to reach our goal or 20 years. ^{*4 ?}

What else have we not calculated in?
 We have not calculated in that for large systems, the price of panels, inverters, battery storage and everything else would be considerably lower.
 We have not calculated in that prices of solar panels are constantly dropping. India has recently announced that solar is cheaper than coal. ^{*8}
 We have not calculated in that new cheaper and more reliable technologies (e.g. perovskite, nanopillar, molten salt storage, etc.) are emerging and lining up for massive production. ^{*9}
 We have not calculated in the efficiency of future solar panels.
 We have not calculated in that when combining solar panels with energy storage (Li Ion battery packs) at places of production (homes), losses that we usually have in grid can be reduced; and that we would use our electric cars as additional storage.
 We have not included losses we would save on oil transport: trains, trucks and oil tankers (4000 of them) will stop using oil (energy) to transport oil. We will also reduce usage of energy for oil rigs, pumps, pipes, and other oil infrastructure. Although, we will still continue using oil to some extent, as it is widely used in plastic industry, at least until we find an appropriate replacement.
 We have not calculated in subsidies. Billions that are spent yearly subsidizing the dirty industry, could shift into the solar industry.
 The International Monetary Fund has calculated that energy subsidies are projected at US$5.3 trillion in 2015. ^{*11} Although it is necessary to take into account that those subsidies are for the entire world with the following breakdown per category: petroleum ($1496.78 billion), coal ($3147.38 billion), natural gas ($509.82 billion) and electricity ($147.75 billion). Also important to note is that the calculation includes: pretax subsidies, global warming, local air pollution, congestion, accidents, road damage and foregone consumption tax revenue.
 We have not calculated in the decreased number of cars on the road because of the selfdriving advances.
 We have not calculated in existing hydroelectric, wind and tidal power plants.
 We have not calculated in investors eager to invest their money in a rapidly growing industry.
 We have not calculated in retirement funds that can invest more in solar energy.
 We have not calculated in all the gasolinebased cars that currently use energy very inefficiently; wasting more energy than they use for useful operation.
Currently in the US 59% of total energy is rejected due to losses for different reasons and similar numbers can be seen around the world. ^{*10}
All the above calculations were made taking into account that we will continue wasting the same amount of energy in the future, which is wrong.
For instance currently we waste around 80% of energy we use for transport; but with new advances, and with electric cars powered of the grid we could reduce that waste dramatically (More about this in the “Energy Efficiency” post) , making the goal of going all solar by 2030 more achievable.
Notes & References:
1. World energy consumption (Trends Table)
https://en.wikipedia.org/wiki/World_energy_consumption#Trends2. Total Surface Area Required to Fuel the World With Solar
http://landartgenerator.org/blagi/archives/127http://www.eia.gov/forecasts/archive/ieo09/world.html
3. British thermal unit
https://en.wikipedia.org/wiki/British_thermal_unit4. Sunshine duration
https://en.wikipedia.org/wiki/Sunshine_duration5. List of deserts by area
https://en.wikipedia.org/wiki/List_of_deserts_by_area6. 285 Watt SolarWorld Sunmodule Plus SW 285 Mono Black
https://www.emarineinc.com/285WattSolarWorldSunmodulePlusSW285MonoBlack7. World Population by Income
http://www.pewglobal.org/interactives/globalpopulationbyincome/8. India says the cost of solar power is now cheaper than coal
http://www.sciencealert.com/indiasaysthecostofsolarpowerisnowcheaperthancoal9. Highefficiency, highreliability perovskite solar cells getting ready for mass production
http://www.innovationtoronto.com/2015/09/highefficiencyhighreliabilityperovskitesolarcellsgettingreadyformassproduction/10. Estimated U.S. energy use in 2013
https://flowcharts.llnl.gov/content/energy/energy_archive/energy_flow_2013/2013USEnergy.png11. International Monetary Fund: Counting the Cost of Energy Subsidies
http://www.imf.org/external/pubs/ft/survey/so/2015/NEW070215A.htmhttp://www.imf.org/external/np/fad/subsidies/data/codata.xlsx
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