Which is better for classical piano practice, the Kawai ES120 or Casio PX-S1100?

The Kawai ES120 is the stronger choice for classical technique. Its Responsive Hammer Compact action has more realistic key depth and weight distribution than the Casio's Smart Scaled Hammer. For players developing finger strength and learning to control dynamics precisely, the ES120 more closely mirrors the feel of an acoustic upright.

Can the Casio PX-S1100 really run on batteries?

Yes — the PX-S1100 can run on 6 AA batteries, making it genuinely portable in a way no other 88-key weighted piano offers. Battery life is approximately 4–6 hours depending on volume. This is useful for busking, outdoor events, or locations without a power outlet nearby.

Is the Kawai ES120 worth the $120 price premium over the Casio PX-S1100?

For serious piano students, yes. The key action difference is meaningful — the RHC action on the Kawai builds proper finger technique in a way the Casio's shorter-pivot action does not. If you're a casual player or care more about aesthetics and slim profile than action realism, the Casio is the better value.

Which is better for apartment use?

Both are excellent for apartments. The Casio PX-S1100 has a slight edge due to its narrower depth (9.1 inches vs 10.7 inches for the Kawai), making it easier to place against a wall. Both models use headphone outputs for silent practice, and neither action is particularly loud mechanically. If slim profile is your top constraint, see The Slimmest 88-Key Digital Pianos — the PX-S1100 is one of five options ranked by depth. If mechanical key noise is the priority instead, see Quietest Digital Piano Key Actions — both score well there too.

Does the Kawai ES120 have Bluetooth?

The ES120 supports both Bluetooth Audio and Bluetooth MIDI via the optional Kawai WU-BT10 adapter (not included). Bluetooth Audio lets you stream music from your phone through the piano's speakers. Bluetooth MIDI enables wireless connection to tablet apps like GarageBand or flowkey, eliminating the need for USB cables.