Load your WordPress site faster by caching widget output using Transient API.
As of version 4.1 you can totally improve your website's performance by using WordPress Widget Cache feature to save widget output on transient for faster retrieval than core widget display.
Should I use WordPress Widget Cache Output?
The answer is yes, specially when you are using widgets with third-party contents like Twitter tweets, Instagram feeds and other services. This widgets will always make call which takes some loading time. Other heavy resource widget outputs and WP_Query calls like Recent Posts, Recent Comments, Pages and other WP_Query relying widgets also adds loading time on your site which you can control using this caching option. You can set time when you want them to be cleared or updated for you to be able to save the fresh one.
If in any case you do not want several widgets to be cached, you can always go to Widget Options settings tab and check the “Do not cache this widget” option. You have the complete control over your widgets!