Some local libraries (e.g. in Heidelberg) or ecological initiatives lend devices to measure electricity consumption at the power plug. In particular, this is useful to measure other appliances as well.
Specifically for computers, they probably have some means to tell you their own consumption, but they may not be accurate or complete and will most certainly omit any peripherals, e.g. external hard drives.
https://www.cambridge.org/core/journals/new-testament-studies/article/origin-of-the-needles-eye-gate-myth-theophylact-or-anselm/51F6B1FD504C36C42D6201F6D87F83C3
Also, more amateur-ish, but trying to get a scoping overview over the arguments against the gate theory: https://classictheology.org/2021/10/12/through-the-eye-of-an-actual-needle-the-fake-gate-theory/