The batteries in my Logitech wireless trackball and keyboard last several months to more than a year. The keyboard in particular lasts really long. I have these on my work computer, so they are getting heavy use.

Bluetooth (BLE) is impressive, I have seen a BLE device being stuck to a window in an office, and with just the vibration of the glass, it created enough energy to send small data packets to a PC 10ft away.

I’m not sure of the answer, but I feel like other commenters are just guessing.

My reason for doubting the dongle is that Bluetooth is designed to be ultra-low-power. We’re talking in the low milliwatts range.

I don’t know how much power a 2.4gHz dongle uses, but I would be surprised if it was less than Bluetooth. However, in terms of laptop battery life, it’s probably not significant enough to really matter. It’s not like either one will cut your batteey life down a noticeable amount.

Not sure but im pretry sure both a so negligible its completely irrelevant

Dongle is better usually

Now that we have BLE (Bluetooth Low Energy) I’m pretty sure it is better than USB dongle. I have a BLE keyboard and a BLE trackball and never used the dongle so not sure how to compare.

Plus it saves 2 USB outlets on my PC :)

chatGPT says:

Bluetooth Low Energy (BLE) typically offers better power efficiency than USB dongles for keyboards and mice, especially when both are battery-powered.

Here’s how BLE compares to USB dongles in terms of power consumption for these devices:

Power Efficiency:
    BLE is designed specifically to use minimal power, especially in low-data-transfer devices like keyboards and mice. It uses an efficient sleep-wake cycle and keeps the radio off most of the time, which conserves energy.
    USB wireless dongles, while not as power-hungry as other wireless technologies, are usually less efficient than BLE because they often keep a more consistent connection with the device.

Battery Life:
    BLE devices typically offer longer battery life. A BLE-enabled keyboard or mouse can last from months to even a year or more on a single charge or set of batteries, depending on usage and the device’s power management.
    USB wireless peripherals, in contrast, may require more frequent charging or battery changes, although they are still relatively efficient.

Sleep and Wake Latency:
    BLE is optimized to quickly reconnect after sleep, so devices wake up quickly with minimal delay. Some USB wireless devices can also wake fast, but the energy consumption during idle periods is generally higher.

Compatibility and Usage:
    BLE is widely supported on modern devices (laptops, tablets, smartphones) without needing a USB port. USB dongles, however, need a USB-A or USB-C port (with an adapter) and are mostly used with PCs.

In general, BLE is better for devices where power consumption is critical, like battery-operated keyboards and mice. However, for some gaming or high-precision tasks, USB dongles may offer lower latency, which some users prioritize over battery life.