We are planning on adding a 3-piece below grade bath (shower, sink, toilet). The kitchen, two baths, and laundry on the main floor are serviced by the usual electric 60-gallon water heater.

The below grade shower will only be used intermittently, like when our grandkids visit. I hate to supply it with hot water all year round when it'll likely only get used 3-4 weeks. We were thinking about installing a smaller water heater near the shower that can be turned off when not needed, sort of like in an RV. I would like to keep hot water to the sink, however. Any thoughts?