You can check googlebot activities under Health > Crawl Stats in your webmaster tools account. If there is a considerable time for downloads which affects your server then you can change the crawl rate under Configuration > Settings.
Go to Configurations -> Settings -> Limit Google's maximum crawl rate. It actually doesn't speed up any index time. If you want your content to appear faster in google use Fetch as google Boot option under health. After fetching submit to index. You content get indexed in 4-24hours.
Google crawl rate is depend on your site content & meta description if your site have fresh and highly recurring content than you got more crawl rate. I thing bandwidth is not affected by increased crawl rate.