Battery Drop of 5% in two hours is not bad
A battery drop of 5% within two hours is not bad at all. How much does it drop throughout an entire day? How long can you use it for taking a few calls, browse a little?
If it only drops heavily, when not in airplane mode, please check your battery usage:
Settings -> General -> Usage -> Battery Usage
Apple offers an about $80 (+ $7 shipping) battery replacement-program for iPhones https://www.apple.com/batteries/service-and-recycling/
Alternatively, if you - or a friend of you - like to fix things yourself you could consider a iFixit iPhone 5s Battery replacement kit, which is about $30 (without shipping) https://www.ifixit.com/Store/iPhone/iPhone-5s-ReplacementBattery/IF124-002-2
iFixit provides very useful guides of how to fix electronic devices from Apple or other manufacturers.
You might want to also check your warranty status: https://selfsolve.apple.com/agreementWarrantyDynamic.do
If you have an AppleCare Protection Plan they might replace the battery for free!