Do I run any risk by accepting the lowest bid?

  Yes. I suggest getting 3 bids. If one is more than 5 to 10% lower than the others, it's likely you're getting inferior equipment and workmanship or they just left something out. Ask questions!

P.S. My favorite motto:

THE LOWEST BIDDER

It is unwise to pay too much, but it is worse to pay too little. When you pay too much, you lose a little money...that is all. When you pay too little, you sometimes lose everything, because what you bought is incapable of doing what it was bought to do.
The current law of business balance prohibits paying a little and getting a lot...it can't be done. If you deal with the lowest bidder, it is well to add something for the risk you run. And, if you do that, you won't have enough to pay for something better.