I had that very problem and the result was rearranging the stuff in the closet. It might actually end up being a better arrangement of stuff than that which evolved over the last 40 years.
I had this one installedby the plumber. Having done it I think twice before I just wasn’t up to it again.
I have occasion to visit a major heater manufacturer and the actual cost increase is not so much in materials but in the seemingly endless rework of processes and systems.
Yes, for an increase in efficiency you'd be hard pressed to notice on you utility bill.