It is essential that you optimize your Joomla. This will help you to load your website faster as well as it will consume less server resources.
This article describes few optimization techniques for your Joomla.
[1] Enable caching for your Joomla installation. You can enable it from your Joomla Admin panel -> Global configuration
[2] If you are showing many post on your homepage, it may take more time to load it. Limiting number of articles and content blocks on the frontpage will help you to load your page quickly.
[3] In your Joomla Admin section -> Global Configuration, enable debugging and then check how many MySQL queries are being generated. This should help you to find any plugins on your site that are occupying excess resources or causing your site to load slowly.
[4] Disable modules, plugins, components that you are not using.
[5] Install other optimization plugin
[6] Use online tools like Google PageSpeed to the suggestions. You can access it from the following URL:
http://developers.google.com/speed/pagespeed/insights/
[7] It is also recommended that you restrict admin area or other pages from search engine bots that you do not want to appear in search engines. You can use robots.txt file to disallow them.
These are the few optimization techniques. There are other options as well.