will a 240w adapter be fine?

My 330W adapter, for my alienware 18 (2013), isn't working anymore. I'm going to buy a new one soon, but I need one now as I'm leaving for a week or so. My friend has a spare 240W Dell adapter and will lend it to me. Will the decrease in power affect anyway performance, or will it simply just take longer to charge? (I'm always plugged in while using it so that wouldn't be a problem)
cheers!

will a 240w adapter be fine?