Is an indirect water heater a good replacement for an electric water heater in a Glendale home with a boiler?

The problem

A homeowner in a 1920s attached brick home in Glendale, a neighborhood known for its intact pre-war housing stock and long-running cast-iron boilers, contacted us about an aging electric water heater that was slow to recover and adding noticeably to the electric bill. The home had a functioning gas-fired hydronic boiler serving original cast-iron radiators throughout, but the water heater had always been electric and separate. The owner wanted to explore whether the existing boiler could carry both loads and whether the changeover made financial sense. The existing boiler had a dedicated indirect port that had been capped off by the original installer. The boiler had been running for nine years fully capable of serving an indirect tank, but the building had been using an electric unit in parallel the whole time.

What we did

After verifying the boiler's BTU output and confirming it had adequate capacity to serve both the heating zones and a new indirect tank, we selected a vertical stainless-lined indirect water heater sized for the household demand, we ran new copper supply and return lines from the boiler's dedicated indirect port to the tank, insulated the runs, and connected the aquastat control wiring so the boiler prioritizes the indirect call before zone calls. The old electric water heater was disconnected and removed. We fired the system, verified the indirect zone was heating the tank to setpoint within the expected recovery window, and confirmed that all hot water fixtures in the home had strong flow and adequate temperature. The owner eliminated the electric water heater from their utility bill entirely. Installed a Triangle Tube Smart 40 stainless-lined indirect tank. Connected the aquastat wiring so the indirect call takes priority over the zone calls. Standard priority logic that keeps domestic hot water available during heating demand.