Power Consuption: Sleep versus Hibernate?

I am clear (at least I think I am) that the difference between sleep and hibernate is that while both preserve open windows, unsaved files etc, so that you carry on as before without loss of data, sleep preserves by saving to memory and hibernate preserves by saving to the hard drive or SSD. As a result, hibernate uses less power than sleep while the machine is hibernating. Both are very quick with an SSD.

Therefore, if the computer is to be left for a long time, hibernate is better (because of the lower power consumption).

But how much power does the average modern Windows 10 desktop computer use while sleeping or hibernating?

Thanks.

According to here and here

Hibernate = none (if you unplug it, otherwise perhaps 3W for LEDs, WOL etc)
Sleep = about 12W

Presumably it would be higher if you are using USB to charge something (assuming they remain powered).

It isn't just power consumption that is different. In sleep the CPU goes into a low power mode and only RAM and a few critical devices receive power. It is very fast to go into or recover from this mode. The downside is that as RAM is volatile it's contents will be lost if power is lost. In that case you risk data loss or corruption. This is not recommended for long periods of time.

In hibernation data is saved to disk which is non volatile. It is like the computer is plugged in but powered down. Power consumption is very low but not zero. You could safely put the computer into hibernation, remove power, put the computer into storage for a year or more, and later restore with all applications open and ready to go as before with no data loss. Some applications might have difficulties but they are usually minor. Because this may require action on their part, processes are notified before the user logs off or the computer is shut down. Processes are not notified prior to sleep or hibernation.

I have a newer HP laptop running Win10, and I was under the presumption that if I disabled Fast Startup, then when I shut down the laptop, it would not draw power anymore.

And, since that is a form of "hibernation", I presumed that would work.

But it does not, because when I shut the laptop down, the battery is charged 100%; when I restart the laptop two days later, the battery is down to 90% or less, and I am Shutting Down the laptop.

The battery is removable, so I could do that if I have to, but I'd rather just not have it draw power when it is turned off.

There is always some power draw even when your system is shut down - the suspend (not directly related to ACPI suspend from Windows) and deep-sleep power wells may both be active even when you are "fully" shut down.

It's up to the laptop design and configuration to minimize power draw in shutdown/hibernate states. For instance, user-controlled features like USB charging, wake-on-LAN/USB, Intel AMT, etc. may be configured to keep some power on even when you're on battery. And the motherboard/embedded controller will use power on their own.

10% drop over 2 days seems a bit excessive so I would check to see if you have any wake sources enabled in Windows and UEFI setup.