Gas Tankless water heater on a 15 unit?

[Jon L.]

Our 100 Gallon, 199k BTU water heater is getting old and needs to be replaced soon. Cost is about $5-6k. 

I'm looking at Quick Water Heater in San Diego and for around that price, they can do tankless. Any idea if that's a good idea? We want it to last 10+ years, of course. The building is about 12k sq ft, single metered for water, and we pay for the gas to heat up the water. The gas bill is almost double what it was 18 months ago.