Many advertisers have observed that their ads convert differently during the day. In fact, hourly conversion rates can vary as much as 50% from the overall average. To maximize your budget you should first find out when visitors are more likely to covert. To do so, log-in to your analytics account, go to Traffic Sources, click on the AdWords tab, and select Day Parts. There, you can see goal completions by hour of day.
If you notice that most of your conversions happen during certain times of the day, say during standard business hours, you may want to run your campaigns during business hours only. This can be set-up automatically within your AdWords campaigns by enabling Ad Scheduling. Be aware that restricting your ads to certain hours only will results in decreased impressions and clicks. However, this may still be a viable option for you, especially if you have a limited budget. Understanding when your ads convert and acting on that information can help you maximize advertising dollars and improve ROI. You’ll avoid spending money on clicks that are less likely to convert and focus your efforts on what’s working for your website.