Hot Water Guys is perhaps the most professional service provider I've worked with as a homeowner, maybe ever. I am a retired professional engineer so know something about the providing of professional services. These folks nailed it.
From the first person I communicated with, to the scheduler, to the service technician who diagnose the problem, to the estimator who came out to size up the job (which was ultimately approved and finalized by their master plumber), to the team of three guys who installed the new machine, everyone was cordial, responsive, knowledgeable, and went out of their way to make sure all of my questions were answered.
They worked together in a seamless way with no wasted motion and nothing fell through the cracks. They kept me informed at every step including giving me a heads up when someone was on the way out, always at the scheduled time, when that service person arrived, and when that person left.
They never left me guessing or wondering about anything, they did the agreed work in a very professional manner, cut no corners, left things spotless, and charged me the agreed price, which I found to be a very reasonable price, especially considering all of the accumulated knowledge I benefited from by hiring then. I couldn't have asked for more.
I have dealt with many plumbing companies over the years who profess to know about tankless water heaters. Mostly they don't.
These folks are by far the most knowledgeable about the topic, the technology in general, and the manufacturers they represent in particular. I highly recommend them to anyone who needs a properly designed, sized, and installed tankless water heater solution without any drama, hassle, flimflam, or other time and money wasters.