Tankless water heater mainly save space not money! Installation costs for tankless systems are much higher than conventional water heaters (e.g. typically 3 to 4 times more than conventional gas water heaters.) Numerous tests by independent third parties have shown only 5% savings versus conventional electric water heaters and 15%-20% savings versus energy efficient conventional gas water heaters over a 24 hour period. It is worthwhile to calculate the payback! Some show between a 21 and 71 year payback to install a tankless heater.
It’s a misnomer to call tankless heater “instantaneous,” as how soon you get hot water depends on the length of the pipe runs. While it is true that electric tankless heater may avoid running out of hot water versus an undersized electric tank but that is only a matter of sizing the electric tank correctly. Residential gas tank heat up faster than electric so running out of hot water with gas tank is less common. The addition of solar further adds to the thermal storage, particularly in the “solar hot water season” when most of the hot water needs are covered by solar alone.
Solar works with either tank or tankless water heaters and heats the water with only the sun. Reduce how much you pay the utility companies each months and pay yourself instead!