This is a fantastic price for a whole-home tankless water heater.
As with most tankless water heaters, the amount of hot water flow you get out of the unit is dependent on how cold the water coming in is. See the Amazon description for an estimate of your state.
Also note, this requires three 40 amp double pole circuit breakers and large enough electrical service to accommodate. 200 amp service to the home is recommended. Check your main breaker amperage if you aren't sure. The warranty requires the unit to be registered within 30 days and installed by a licensed electrician/plumber. If you plan to DIY, you may consider a SquareTrade warranty.
Check for local rebates from your state/county/electric provider.
Average savings for going tankless are 24-34% of water heating costs according to the Department of Energy.