Solar-Powered Calculators: The Solar Energy Device For Your Pocket

Solar powered calculators are fascinating gadgets. But before understanding their functioning, let’s discuss the basic components of solar devices– solar cells. 

Solar cells utilise the sun’s energy to power the connected devices. Being made of a semiconductor silicon diode, they transmit electric current to generate power. 

They find applications in domestic and commercial fields. Read on for public and personal devices fuelled by renewable energy sources.

Public Solar-Powered Devices

Solar-powered parking machines are gaining popularity. They provide flexibility in site selection and recycling; thus, assisting the planet in multiple ways. Additionally, they reduce commercial and residential installation costs and underground wiring. 

Another example is speed warning signs that provide the same benefits.

Apart from these devices, multiple other public places witness solar-powered devices successfully functioning for long periods. These are street lamps, solar LED road signs, and traffic lights. 

And, solar powered calculators are used to measure the efficiency of such devices that run on solar energy. 

Common and Handy Solar-Powered Devices

Few personal devices such as toys, watches, clocks, keyboards, emergency lamps, and many more contribute to an eco-friendly approach rather than generating non-recyclable electronic waste. 

Pocket-friendly calculators are significant solar powered devices for everyday usage by the common person. 

The solar powered calculators are power efficient and have liquid crystal displays and voltage output ranging from 1.5 to 2 volts. 

Conventional solar powered calculators require sufficient light for function. Texas Instruments addressed the problem in the 1980s through Anylite Technology. They incorporated large photovoltaic solar cells to solve the issue. 

The Anylite technology in TI solar powered calculators is indicated by the lowercase alphabet ‘a’ in modern devices. Older devices have Anylite Solar impressed on them. However, 2010 witnessed solar-powered calculators that ran solely on battery. 

Recognise Solar Powered Calculators

Low batteries in solar-powered calculators can be recognised through signs, which can also identify original solar-powered calculators. 

The signs are as follows:

  • – Darkness or light blockage will fade the numbers and lag the operation. 
  • – It is further evident by the time gap between pressing the number and the change in display. 

Maintain Solar Powered Calculators

While using solar-powered calculators, ensure usage in a bright location but far from direct sunlight. Direct sunlight for the chronic state will damage the receivers in solar panels. 

Also, panels should be regularly cleaned for efficient functioning and to inhibit the accumulation of dirt that eventually blocks the sunlight. 

Impurities like oil and dirt from hands result in refraction, decreasing the efficiency and increasing the loss of solar lights. Inbuilt plastic covers prevent direct damage and facilitate cleaning. 

Factors Affecting Solar Charging

The charging time can be easily calculated through the available formulas. While not going into the technical part, we provide two assumptions and shortcomings that hold significance in calculating charging time and are important to be aware of. 


  • – Solar panels are completely efficient

No device in the world is completely efficient due to various factors. The same is the case with solar powered calculators, which require Standard Test conditions or ideal conditions to output rated power. 

These conditions are 25 centigrade cell temperature within the panel, with 100 W/m2 solar irradiances and 1.5 air mass. The impossibility of ideal conditions, accompanied by other factors like shading time and region, hampers efficiency. 

  • – The battery has no connections

The power stored in the battery is shed through the movement of charge into the connected device. 

The usage of that device takes the battery’s power, increasing the charge time. A minimal power-taking device, a solar charge controller, is usually connected to the battery. However, this device might also suck up the power in certain conditions. 


  • – Rule of thumb is not always applicable

A rule of thumb is incorporated to simplify the calculations. Yet, the limitations posed due to several factors decrease the efficiency, further modulating the output. 

For instance, temperature, photovoltaic and battery voltage distinction are responsible for changes in the efficiency of PWM and MPPT charge controllers. 

Similarly, charge affects the output power generation in lead acid batteries. Thus, each system has several factors affecting its efficiency. 

  • – The specific duration of the absorption stage

While calculating the charge time for solar-powered calculators, often, the duration of the absorption stage is ignored. The absorption stage refers to the phase when the battery reaches a specific voltage which is the completely charged phase. 

At this time, the charge controller is in an absorption stage for the remaining charge cycle, where the former varies for different types of batteries. 

The stage witnesses reduced current flow. For instance, lead acid batteries have two hours of absorption stage while lithium-ion batteries have a 20 – 30 minute absorption period. 


Solar cells have found wide applicability owing to environmental and electricity benefits. The possibility of usage in numerous devices, both public and private further increases the benefits. 

The solar powered calculators are one example of hand-held devices utilising solar energy. The solar cells show greater than 98% efficiency, with loss in energy occurring due to environmental factors. 

Proving a great boon to society and incorporating the latest technology, they are a great hit in today’s market. 


1. Are solar powered calculators reliable?

Regardless of the power source, calculators are designed to be 100% reliable. Sun powered calculators rarely make mistakes. 

However, minor errors might slip in when the batteries are nearing flat as they fail to recognise the buttons you are pushing.

2. Can you charge a solar calculator with a flashlight?

Solar calculators contain amorphous crystalline silicon solar cells. It indicates lower power requirements. 

Thus, being low-powered, they can be charged through flashlights and other sources of indirect light such as fluorescent bulbs, home light bulbs, and incandescent lamps. 

Solar calculators are recommended to be charged by a bright source of light. Experts prohibit the direct use of the sun to charge them. 

3. Do solar powered calculators stop working?

The estimated lifespan of solar powered calculators is around five to fifteen years. 

Although, practical usage has claimed solar calculators to last more than twenty years. With simple maintenance activities like regularly cleaning the solar cells for maximum light absorption and removing oil and dirt, one can increase the solar calculator’s life.