To calculate the overall star rating and percentage breakdown by star, we do not use a simple average. Instead, our system considers things like how recent a review is and if the reviewer bought the item on Amazon. It also analyses reviews to verify trustworthiness.
It's powerful enough for home use. Battery last reasonably long. This is my second purchase of same model. First one was purchased more than 3 years ago and recent damaged by accident. Really a good stuff.