I can see the importance of maximizing the battery life of your MacBook, @E30.
The performance and battery consumption depends on the spec of the device you are using. As the Mac device seeks the best performance of their applications, in result to more battery consumption.
You can check any installed application, such as anti-virus or anti-spam software, that may trigger a speed bump using the QuickBooks Online App.
If you're worried about disabling your anti-virus, you may use Safari to maximize battery life. You can always access QuickBooks Online using your browser at qbo.intuit.com. The browser and app version of the software work almost the same.
I appreciate you for providing additional information and a screenshot above, E30. This leads me to the right resolution on how to minimize the battery consumption of your MAC devices using QBO Desktop App.
Based on your screenshot, the QBO Desktop app has the highest energy impact. It's possible that the app is now full with the stored cache. That's why it quickly consumes your Mac CPU's storage.
To lessen the QBO Desktop app's power usage, you can reset its data to refresh it. Here's how:
Go to the Help menu at the top of the screen.
Select the Reset App Data option.
Allow a moment for the process to complete, and then close the app.
Once done, you can check the app's battery consumption in the Activity Monitor window to verify the update.
In case the app still uses the same amount of your MAC's battery after performing the steps above, you'll have to uninstall and then reinstall it. This will restore the application to its default settings.
To uninstall the app:
Drag the QuickBooks app from the Applications folder to the Trash.
Go to Finder.
Select Empty Trash to completely remove the app.
After the process, you'll have to re-install the app. You can check out the How do I install the app? section in this article for the detailed steps: QuickBooks App for Windows and Mac. It also contains information about the supported OS for MAC and how to use multiple windows in the app.
Please let me know if you have other concerns. I'm just around to help.