Sunday, June 10, 2012

My Favorite Solar Calculators of all time

In no particular order...

Texas Instruments TI-25X Solar - mid to late 1990s

This small calculator packs a lot of punch. 8 digit that converts to 5 digit with 2 digit exponent any time the number exceed eight digits. Features include reciprocal, polar/rectangular conversion, one variable statistics, and decimal-DMS conversion. When I had the TI-25X the first time, back in the late 90s, it was my go-to calculator for quick calculations. I just bought another one from Amazon a week ago.

The calculator is truly solar, that is no batteries are used in any operation, which is rare in solar scientific calculators. (The battery, I think, aids long-term memory storage).

The trouble with the 25X was protecting it. It now lives in a small camera case with bubble wrap around it when not in use. I wish Texas Instruments was still manufacturing the 25X.

Casio FX-115ES Series - 2004-present

This is my favorite calculator Casio has produced. Not only the calculator operates on solar power, but it also was the first (I believe) calculator to have calculus functions: integral, derivative, and sum of a function. Matrices and vectors are also featured. The calculator can solve equations in one variable. Entry of mathematical expressions is straight forward. You can set the calculator to textbook entry mode or linear (classic) mode. I prefer the latter (the less pairs of parentheses I have to track the better).

The 2012 revision, fx-115ES PLUS (pictured), adds, among other things, integer factoring, verification tests, and product of a function.

Outside the United States, this calculator is named the fx-991DE/ES (PLUS).

Texas Instruments BA 35 Solar - early 1990s
(not pictured :( - I don't have it anymore)

Anyone who can operate a BA 35 or a BA II Plus should feel comfortable with the BA 35 Solar. The BA 35 Solar has the following:

* Time Value of Money, using periodic interest rate.
* Cost Sell Margin/Markup calculations
* Interest Conversion
* Amortization
* One variable statistics.

I gave my BA 35 Solar to my dad and he loved using it. Unfortunately, the display went nuts and it had to be retired.

Texas Instruments TI-36X Series (TI-36 Solar: 1986-early 1990s, TI-36X Solar: 1993-present, TI-36X Pro: 2011-present)

If you wanted the most advanced non-graphing calculator, you pretty much went for the TI-36X series. The original TI-36 Solar was powerful non-programmable calculator which had base conversions, hyperbolic functions, normal distribution calculations, and complex numbers (limited to arithmetic). When Texas Instruments upgraded the 36 to the 36X, the normal distribution calculations and complex numbers were dropped, but eight scientific constants, eight metric-English conversions, and linear regression were added.

This calculator received a lot of use during my days of middle and high school. I owned the original 1993 design and it went with me everywhere I went. The solar panel was punctured by a pencil and it died. Eventually, I got the 1996 design (pictured) and is my favorite design of the TI-36X Solar. Texas Instruments redesigned the calculator in 2004, giving it a gray faceplate and white keys, which I also have.

In 2011, Texas Instruments released the TI-36X Pro (named TI-30X Pro in Europe), which a serious upgrade of the 36X series. New features include derivatives, integrals, tables, equation solver, and entry in textbook format. For me, I had to get used to the keyboard because a lot of the keys cycled through functions. An example: the sine key (sin, sin^-1, sinh, sinh^-1), math constants ( π , e, the complex number i ), and the key that annoys me the most, the variable key (x, y, z, t, a, b, c, d).

If you waited to 2012 to consider getting a TI-36X Pro, you did a good thing in waiting. The early versions were buggy and were erroneous in calculations involving π and fractions. Thankfully, TI fixed the bugs and now I can confidently use the TI-36X Pro.

Casio fx-3650P: 2002 - present?

Casio, I think, is the only manufacturer of calculators left that produces programming calculators that also operate on solar power (with battery). I purchased this calculator on eBay (unfortunately it is not sold in stores in the United States, it should be IMHO).

The calculator has 360 program steps on which 4 programs can be stored. The programming language is a simplified set of the programming commands found on the Casio fx-5800p and its graphing calculators. Commands include LABEL, GOTO, basic testing, input prompt, and output.

Other features include complex number arithmetic, base conversions, and Numeric integrals.

Victor V34 - 2000s

Take a good loom at this calculator. If this calculator reminds you of the super popular Texas Instruments TI-30X IIs, it is because the keyboard design is similar.

While the TI-30X IIs sold in many colors for the 2009, 2010, 2011, and (I'm expecting) 2012 back to school seasons, the Victor V34 offers a feature that the TI-30X IIs doesn't: base conversions and logic operations. I purchased this hard to find calculator in a local stationery store in Glendora, CA.

Sharp EL-W516 Series - 2000s - Present

There are two functions two versions. The original had a gray faceplate. Sometime in 2011(?), Sharp made a design change and made the entire plate black. The model is now the EL-W516X with black keys, white, green, and gold lettering. In the United States, the Sharp calculators can be found at Target stores.

Like the Casio fx-115 ES, the Sharp EL-W516 series offers entering calculations in textbook format. Unlike the fx-115ES where you can get exact or approximate answers when demanded, the EL-W516 forces you to cycle through the format of the answers (exact/mixed fraction, improper fraction, decimal approximation) with the press of the CHANGE key (this applies to Normal mode).

The Sharp EL-W516 series offers unique functions:
* Drill feature - a quiz of arithmetic problems
* Functions with lists
* 4 definable function keys
* 4 definable formulas (I love this feature)
* Pental Numbers (Base 5)

That is a list of my favorite solar calculators. Eddie

This blog is property of Edward Shore. © 2012


  1. This comment has been removed by the author.

  2. Eddie,

    How are you? It is me again!

    I bought my TI-36X Pro at the end of March 2012 from Amazon and I can confirm that it still have the error in calculations involving PI and fractions.

    Perhaps I bought an old stock? I even remember returning my item to Amazon because of this bug hoping they will send me a newer stock but still the same problem so I thought that perhaps Texas Instruments never fixed the bug.

    May I ask where you bought your TI-36 X Pro? I tried to look for it on Wal-Mart but I couldn’t find it.

    Many thanks!

  3. Update 6/13/2012:

    Today I went to two different Staples stores and bought two different TI-36x Pro, one came in a green label package and the other in a red label package, unfortunately both of them still have the error in calculations involving PI and fractions. (Of course I returned both calculators and got my money back).

    Any idea if Texas Instruments finally fixed the error? or perhaps it was never fixed? pi*12.5^2 stills shows as 156 pi/4 and NOT 156 1/4*pi

  4. jcroot,

    First I think I deleted one of your posts by accident. I am sorry, nothing intentional I promise.

    Second, that sucks that you have not been able to find a correctly working model.

    I got my bugged and correct working model both at Office Depot. (the first in Summer 2011). Before I got another TI-36X Pro, I tested it by pressing the buttons (pressing against the plastic) before I purchased it. I would not recommend going on line and test the TI-36X first (if you can).


  5. Eddie,

    Thank you for your reply, as I said before I got my first TI-36x Pro from Amazon and 2 more from two different staple's store but unfortunately all of them were buggy. I will give it another try at Office Depot and see what happens.

    By the way, I know I already asked you this question before but I would like to know your opinion one more time, which calculator would you consider the "best" and most "powerful" in general terms? TI-36X Pro or Casio 115ES Plus?

    Many Thanks!

  6. As far as power - both. I like the integration of the TI-36X better but the fx-115ES PLUS is on par as far as features go.

  7. Eddie,

    Yesterday I went to an office depot store and did what you suggested me (testing the TI-36x Pro) before buying it but unfortunately it also had the pi and fraction bug. I guess I am giving up and perhaps I will never have a fully working TI-36x Pro :(

    Also, I just wanted to mention something interesting that I found out after playing around with my TI-36x Pro and comparing it to my Casio 115es Plus:

    Both calculators are able to solve this equation:
    3(x+5)=2(-6-x)-2x ( solution: x = -27/7 )

    But... only the TI-36X Pro is able toggle the answer into a fractional form -27/7 while the Casio 115es plus only gives me a decimal form -3.857142....

    1. This comment has been removed by the author.

    2. Eddie,

      I just want to add to my comment something also interesting that I just found out:

      Equation: (5)/(2x-6)=(10-x)/(x^2-6x+9) (Solution = 5)
      The TI-36X Pro is able to solve this equation (although it takes a while) but the Casio 115es Plus returns an error: L-R = -1.6758...

      Update June 15, 2012 (6:41 PM Eastern Time):

      After reading the manual I found out that the Casio 115ES Plus uses Newton's Law in order to solve equations and therefor if there is an equation that can't be solve we must input an initial guess for the variable that we are solving for, in this case I input 4 and it worked, the calculator gave me the right solution X = 5.

      Any way, maybe the TI-36X Pro is better at solving equations?

  8. Jcroot, I get x=5 with L-R=0. I am in Norm 1 floating mode. (still don't know what that means LOL).

    For reference, my TI-84+ returned x=4.99999999997.


    1. Eddie,

      I get also X=5 with L-R=0 only when I enter 4 or 5 as an initial guess for the variable X. Are you also entering the initial guess? or are you getting the right answer just by entering the equation?

  9. Jcroot, By entering the initial guess.

  10. FYI...

  11. SelectArrow,

    Yes. I am aware of the bug the early 36X Pros have. Thankfully, the bug was fixed in the later production models. Never hurts to test before buying.


  12. Hi Eddie - my point (or the point of the article) is that it's not a bug 625/4 is 156 and 1/4 x pi = the same answer... the TI36x was being consistent (in it's own peculiar way)...

  13. Regarding the TI-36x Pro.

    Wikipedia annonce : "As of February 2013, a fixed revision has not been released and the error is still present in all shipping TI-36X Pro calculators."

    We can find the the bug presentation on YouTube "TI-36X PRO Programming Bug" => ""

    I just reported it to TI by phone communication and I'm waiting for an anwser.
    How my Mathing Faculty did to close their eye on that?
    How TI can do nothing?
    How can I trust tool to get the success I'm suppose to get?

    Hope TI do something soon!

  14. An Easy Way to Upgrade to Universal Analytics?... Home solar panels

  15. This comment has been removed by the author.

  16. TI-36 see Programming errors
    I asked to TI what about this, then nothing.
    However this calculator seem to be very good, so what about those errors (true|false)?

    1. Steve,

      If memory serves me correctly, doing a reset on the TI-36X Pro should correct the "pi" error.


  17. The TI-25X Solar on your list has ~ functionality as the Casio FX260 Solar, as low as $6 and still in production. For basic functions it works superbly as solar cells are very well engineered to the electronics, even in dim light it works.

    Great blog, keep it up!


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