The hotplate should have a sticker or imprint on the bottom or somewhere else on the hotplate but hotplates usually use around 1,000 watts of electricity.
I use one at my house and the hot plate doesn't raise my electric bill that much even though I use it everyday to cook on.
They're not constantly on like an electric space heater would be so your hotplate shouldn't use that much electricity in a month and shouldn't cost you that much to use.