This advice is based on personal opinion only, and although it is designed to help you. Marycliff Piano Lessons are not responsible or liable for any actions you do or do not take as a result of reading this article.
How many notes and what size?
Choosing an electronic keyboard or digital piano of at least five octaves with 36 white notes C to C (60 notes including black and white ones), is the minimum for students to follow piano lessons. If you have a six and a quarter octave or even a full-size, seven and a quarter octave keyboard, then it would be even better, and will last you a lot longer. A six and a quarter octave keyboard does fine for most people, because the number of pieces where you use the notes at the extreme ends of the keyboard are only a small proportion of the piano repertoire.
One octave on your keyboard should be 187-188 millimetres measured from the left edge of one C to the right edge of the next C. This is the usual size of acoustic piano keys, but there are many models in the lower price ranges which are not full size - so take a metal tape measure to the shop when you buy and electronic piano or keyboard. The smaller size notes will not bother you if you don't want to change over at any time to acoustic piano or to a better keyboard. If you do change over, it will cause you problems. Your brain will have to relearn everything you play and get used to the full size notes - this can be quite a painful experience and can take many weeks or months.
The touch sensitive action of digital pianos
Important: if you strike the key harder, then it should play louder and vice versa. The harder the touch, the closer it will be to an acoustic piano, and will therefore be better for your technique. There are actually different degrees of touch sensitive (hopefully adjustable). There are semi-weighted keys and fully-weighted keys: the fully weighted are usually more expensive, but are closer to the feel of the acoustic piano and therefore better for you. This is a tremendous improvement and makes the whole experience more like an acoustic piano. If you don't have a touch sensitive keyboard, you can still learn the music, but there are some musical refinements of interpretation which will be impossible for you to achieve. It also makes it very confusing if you ever want to cross over from electronic to acoustic piano. In addition to having touch sensitive actions which can be adjusted to your personal taste, more modern hybrid electronic pianos include an actual hammer action, just like in an acoustic piano. Great to have the choice if you want it. It's very important to take your time and try lots of keyboards and digital pianos so that you combine this article with real awareness of what is going on in the design of instruments, so that you buy one which you are very happy with and which will last you a long time.
Escapement action on digital pianos
This is only obligatory for advanced students. Escapement is the part of the piano action allowing the hammer to return to a temporary resting place after you have depressed it. This means that you can play the bed of the key - meaning that you re-depress the key before it has cone completely up to the surface and use this escapement mechanism to play repeated notes more quickly and above all quietly. Very useful, for example in part of Fur Elise by Beethoven. Now that electronic pianos have escapement, they are that much closer to acoustic pianos and this is really a very significant improvement.
Pedals on the digital piano or keyboard
Right pedal - essential on your keyboard. Make sure that it's one which is like a lever (down is ON and up is OFF) and not like an ON/OFF switch. The right pedal - sustaining pedal - of your electronic keyboard or piano is the one which makes the notes carry on playing even if you take your finger off them. The notes will continue to sound until you lift your foot off the sustaining pedal.
Una corda or soft pedal
Left pedal - useful but not obligatory. If you have one, it should be working properly by making the notes quieter. The una corda pedal is so called because on acoustic grand pianos it moves the whole keyboard so that the hammers play only one or two strings instead of two or three. On upright acoustic pianos there is a different mechanism which does not make the keyboard move. Not all electronic instruments have a una corda, and if they do - the keyboard doesn't move. You can manage very well without a una corda pedal.
Middle pedal - useful but not obligatory. This is depressed after you have played the note, but whilst it is still held down, thereby enabling you to make certain notes last longer whilst you play other notes affected by the right or sustaining pedal.
Useful but not obligatory. These are so that you can connect to other things like amplifiers (ask your dealer about this) or midi - IN, OUT and THROUGH (usually 5 pin din type sockets or USB) so that you can connect to other equipment like computers other midi keyboards, sound modules and midi sequencers. The midi connection system is invaluable if you want to compose music via the computer, or to link many keyboards together.
Useful but not obligatory - so that you can practise even when your family is watching television. Earphones are very helpful if you don't want anyone to hear you practise thenew piece until it is ready, or the tricky passage which hasn't quite clicked into place yet. Use earphones carefully, however, because prolonged use is not good for the human ear, which has evolved a lot more slowly than modern technology. Many manufacturers are now putting warnings on their products. Professional sound-engineers only use earphones very sparingly, probably to look after their hearing and only to pick up very tiny details - the audio equivalent of a magnifying glass if you like. So prolonged practice on you keyboard or digital piano is not a good idea.