First time pressure washing my driveway - what PSI do I need?

Never used a pressure washer before but my driveway is covered in mold and stains. It's a concrete driveway, probably about 20 years old. What PSI should I be looking for? I see ones ranging from 1500 to 4000 PSI. Also, is gas better than electric for this kind of job?

For concrete, you want at least 3000 PSI. Anything less and you'll be there all day. Gas is definitely better for driveways - more power and you don't have to deal with cords. Look for something around 3000-3500 PSI with a decent GPM (gallons per minute). The higher the GPM, the faster it cleans. I've got a Simpson gas pressure washer and it works awesome.

Just be careful with that PSI! 3000+ can damage concrete if you're not careful, especially if it's older. Start with a wider nozzle (40 degree) and work your way down to 15 or 25 if needed. Hold the wand about 12-18 inches from the surface and keep it moving. I made the mistake of getting too close on my first try and left marks in the concrete. Learn from my mistake!

Thanks for the warning! I'll definitely start with the wider nozzle and keep my distance. Should I use any cleaning solution or just water?

For mold and tough stains, definitely use a detergent. Most pressure washers have a soap injector - use a concrete cleaner or just some trisodium phosphate (TSP). Apply it with a pump sprayer, let it sit for 10-15 minutes, then pressure wash it off. Works way better than water alone. Just make sure to protect any plants nearby - the runoff can harm them.