The moment you quote hours, you are negotiating your own speed, and every year you get better at the job you earn less for doing it. You have also handed the customer a running meter to worry about, which makes them slow to answer questions and reluctant to ask for anything.
Quote the outcome. What they end up with, what is included, how many rounds of changes are in the price, and what happens if they want more. Then how long it takes you is your business, which is where it belongs.