The ideal piano is not just a grand piano, but a "concert" grand piano. Every piano manufacturer designs their concert grands to have the finest feel and tone quality—to be "top of the line." However, that means that these instruments are upwards of 9 feet long, weigh nearly 1000 pounds and cost in excess of $150,000 dollars. They are certainly worth their cost regarding the refinement of the instrument's regulation and quality of materials, but they are not practical for everyday in-home or in-studio playing.

The generally accepted size of concert grand pianos is a fine balance between quality and practicality. The size balances a scale that produces a glorious tone, with a good feel, in an instrument that is not too large to maneuver and transport, and that is not too expensive to produce and sell. (The scale is a multitude of factors including the string length and thickness, and where the hammer strikes the string.) Piano technicians recognize that the laws of physics dictate that the scale for a near-perfect sound would be an exceptionally long piano (around 14 feet long by some estimates). The largest commercially available concert grand piano is the Fazioli F308, which is 10'2" or 3.08M. Perhaps the largest piano produced today is David Klavins' M470i, which is so large that the only option was to make it a vertical concert grand two stories tall (14'9").

It's truly something to behold: https://www.klavins-pianos.com/products/model-450i/

It is the scale and sound quality of the concert grand piano that all other smaller size piano attempt to emulate. But the laws of physics make it impossible to achieve. Unfortunately, as a piano scale decreases (for all intents and purposes, gets shorter), the sound and touch suffer. Short "baby" grand pianos, even from the finest manufacturers, often sound tubby in their low end and lack beautiful singing sustain.

The next step is to make the piano an "upright" piano. And where large uprights can achieve a scale not possible in the smallest grands, the mechanics of the action are totally different, requiring extra measures to fake the feel of a grand action. 

Since I'll never own a concert hall in which to house a Steinway D, my next favorite piano is a Steinway model B. It is the piano I have seen in every college piano professor's teaching studio that I've ever laid eyes on (typically two in each, in fact), and the one that I dream of having in my own home one day. Yet at 6'11" this is still an exceptionally large instrument for most homes, and at $35,000, it still costs as much as a new car.

If these were the only instruments to purchase few would ever begin playing the piano. Thankfully, a new piano doesn't have to break the bank.

So, what is the perfect piano for a beginning student?

The truth is, that any keyboard has educational value. Yes, even a $15 "toy." A cheap electronic toy keyboard with working white and black keys will serve to familiarize the student with the layout of a full-sized instrument. Plus, these toys have built-in songs one can play along with and make music! Isn't that the point of studying music?! Even when with acoustic pianos, a beat up old spinet can help one learn music. It doesn't have play-along tracks or various sounds, but it has a full-sized, velocity-sensitive keyboard. I guess I could go on and on about various price points of keyboard instruments, but what you really want to get it something of value that will last many years.

Lasting Value

What you are looking for is something that will sound great, feel great (like a grand piano) and last as the student progresses. Thus, I am an advocate for a student's use of high quality digital pianos. A digital piano doesn't need to be tuned and isn't susceptible to changes of humidity like acoustic pianos are. I will need to have my acoustic piano tuned at least twice a year at $100 a pop, and I am seriously considering having a humidistat system (a Dampp Chaser) installed for $400! It's said to last only for 5-10 years!! 

I highly recommend Yamaha digital pianos, especially those of the P series (e.g. P71, P125). Look for bundle options that come with a stand, sustain pedal and bench. These can be found for $600-$700. The Yamaha Arius series is an attractive, high-quality digital piano that has three pedals and comes as a built-in console style cabinet. Its price tag  generally starts around $1000 but its capabilities and quality match the price.

Avoid digital pianos where you can put your finger UNDER the front of the keys. This style of keyboard is similar to a pipe or electric organ, but doesn't at all match the weight and feel of a modern piano. It's typically found on cheaper electronic keyboards these days. (Again, everything has its value, but we're looking for something that will last as the student improves). 

In terms of cost, even a $1000 digital piano beats an acoustic piano regarding maintenance alone. I had a broken key on my Alesis digital piano that I had fixed for $60 a few years back while living in Los Angeles. That's the only repair I've ever needed on it and I have owned it since 1997. It has followed me from New Jersey to New York, Florida, California, and now Minnesota! (It's the one that I use making my online videos because it's in tune!)

Check your local retailers for these instruments and more. Major musical instrument dealers like Sam Ash and Guitar Center will have models like those mentioned here.

PS Check out this link for demonstrations of various types of pianos: https://carusopianos.com/browse-pianos/grand-pianos