I looked at the Aquastar 125 and 240 a few years ago, but the flow rate
was too low for my house. If you are considering a tankless for a
whole house, look at the gas requirements, flow rate and how it
regulates temperature. Also, they work much better if you have a
recirculation pump.

I have been using a Takagi tankless for a couple of years and it has
been terrific. My inlet water temperature in a cold winter is about
49F and it raises it to 117F with about a 4.2g flow rate. In the
summer I get about 6g flow rate.

My rationale for the heater was endless hot water and efficiency (85%).
A high efficient traditional water heater will give you equal savings
without the endless water.

Regards,
John