It’s important to consider the power usage on the 5V line supplied by the ZX Spectrum, as the voltage regulator inside the ZX Spectrum has a limited maximum current.
Some measurements:
| Current | |
| ZX Spectrum 48K without peripherals | 0.40 A (max 1 A) |
| ZX Spectrum 128K toastrack / +2 without peripherals | 0.75 A (max 2A) |
| ZX-HD with Raspberry Pi Zero | 0.14 A |
| ZX-AY | 0.10 A |
| DivMMC EnJOY! *mini* | 0.08 A |
| DivMMC EnJOY! with GAL (until v2015.x) | 0.12 A |
| DivMMC EnJOY! with joy CPLD (v2017.x and newer) | 0.10 A |
| DivIDE | 0.21 A |
| Kempston Joystick interface | 0.06 A |
| K-Mouse Turbo (2008) | 0.12 A |
| PlusDlite | 0.27 A |
| Interface 1 + Microdrive | 0.05 A |
| Interface 2 + DIAG ROM | 0.01 A |