Will mining significantly increase the power consumption of my PC?
Yes it will. The component you're likely to use for mining is your video card (GPU) which consumes very little power when idle but can consume a great deal under load. Check this list of common cards and consult the Watts (W) column for how many watts your card is likely to draw. Any card worth mining on will probably draw at least 100 Watts under full load. Depending on the electricity costs in your area, it may cost you more in electricity than your coins produced are worth. There is at least one good calculator to estimate your proceeds but you'll need to find out how much your local utility company charges per kilowatt-hour for electricity to determine if it's profitable. For reference Kilowatt-hours per day = Watts * 24 / 1000.