Short answer: no. Not to -start-. Not for 6 months or so (up to about 9 months for a student aged 5 and below).
And now for the long answer! First of all, what do you mean by electronic keyboard? Is this a digital piano (such as a Korg, Roland, or Yamaha)? Or is it a synthesizer (such as a Casio)? (Note: Yamaha makes both!) These are two different animals; what makes them different is how the sound is formed.
Usually when people say "electronic keyboard," they are talking about a synthesizer ("synth"). Other names: portable keyboard, digital keyboard, or keyboard.
The prime reason not to purchase a real piano is cost. A real piano is most expensive. A digital piano is in the middle range, and a synth is quite a bit less.
Space is a second consideration. Let's face it: a piano is not a small thing! And it needs to be put in a protected place.
Third, some families don't want to buy a piano until they are sure that piano lessons are going to "take" on the child. An electronic may be easier to sell, they say, if things don't work out. If it's not possible to sell it, then the child can still fiddle around on it and perhaps rekindle interest in lessons at a later date.
A fourth reason to purchase a synth - - or a digital - - is the MIDI port. If you want to be able to hook up your computer to this keyboard, you need a MIDI port.
And, last, more and more commonly, some people want to buy an electronic instrument because of the "earphone" option (they live in an apartment building, they can practice only late at night or before dawn, when the rest of the family is sleeping, etc.)
Of all these reasons to not buy a real piano, cost is the overriding factor in 90% of the cases.
I also have a file about piano brands and costs. The first part of the file is a discussion of pianos by brand names. Price averages for comparisons' sake, as well as some recommendations by my tech, are given directly afterwards.
How are the three instruments different?
In a piano, the sound is produced by a felt-padded hammer hitting a string under tension. The piano really is a percussion instrument! The harder you hit it, the louder it plays.
In a synth, the least expensive keyboard under discussion here, the sound is produced artificially by manipulating sound waveforms.
A digital piano is an instrument in which real piano sounds have been "sampled" (captured electronically) and used to create the digital piano sounds. The digital piano sounds better than a synth, but it still sounds artificial - - and not like a real piano - - no matter what the salespeople tell you.
And they will lean on you pretty heavily since a cheaper item is easier to sell, which means they're more likely to make the sale (and commission) if they tout something less expensive than a real piano. People make decisions based on what they know and the criteria that are important to them, and since price is an important factor for almost everyone, the salesperson has the best shot with a synth.
A digital piano is much more expensive than a synth.
It generally takes more floor space but does have an earphone jack. A MIDI plug is not standard, so if you want one, ask (and expect to pay extra for it).
Ok, so, yes, something electronic (a synth) to start is just fine. It will serve the beginner well in learning where the notes are located vis-à-vis the printed page and a host of other tasks the beginner must complete.
What a synth will -not- teach is piano touch. Even one with "weighted keys" and ones that "feel just like a piano" (per the salesperson). There just isn't a substitute for a "real" piano. I'm sorry to tell you this, but it's true.
For a child beginner, you need to make the investment in a piano after about six months; two to three months for an adult.
Even a digital piano won't do the job of simulating true piano touch, in all honesty.
Solution: rent a piano.
You're better off doing this until the time you're ready to buy a real piano, rather than buying a synth or a digital piano.
If you absolutely want to go electronic, buy a synth (but not a Clavinova) rather than a digital piano because you'll have less invested, and I know you're going to want a piano in pretty short order.
If it helps you make a decision: every student I've ever had who started with a a synth bought a real piano within a year - - often within three months.
If you possibly can, buy a real piano for the beginner (or rent one).
There is further discussion of this topic regarding a digital piano vs. electronic keyboard on my questions and answers for students and parents. Search on "real piano".
copyright 1998-2003, Martha Beth Lewis, Ph.D.
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