Laptop computers have different wattage uses and it also depends on the wattage of your laptop plug in adapter.
But laptop computers use between 65 watts and 90 watts of electricity which isn't all that much.
So if you leave your laptop computer on for 8 hours per day you wouldn't even use 10 cents worth of electricity per day depending on your electricity rates.
In 30 days you would use around $2.10 per month to use your laptop which is pretty cheap.