Where did water heater premium vs. standard penetrations come from?

[jmaguire1]

Someone emailed the ResStock email asking about our "Natural gas, premium" water heater. I was able to answer their questions just fine, but it did lead me to look into the stock saturation of standard vs. premium options: https://resstock.readthedocs.io/en/latest/workflow_inputs/characteristics.html#water-heater-efficiency

Is there any documentation on how we decided how many standard vs. premium WHs are out there for storage water heaters of each fuel type? In both the .tsv and the documentation we list this as coming from the RECS microdata, but I can't find anything related to WH efficiency in the code book. We got HPWH data from another source I think specifically because that info wasn't in RECS? Electric Premium in particular looks really high to me, but I don't actually know of any data source for standard vs. premium myself. My guess is someone made an assumption about this at some point and it never got documented, does anyone know?

[rajeee]

I looked into this and looks like we are assuming that standard water heater with blankets are the premium water heaters.

[shorowit]

We do have the ability to specify water heat tank jacket insulation in OS-HPXML, so it seems like we should use that instead of a premium water heater option for clarity.

[jmaguire1]

So estimation is basing this on whether there's blanket insulation on the tank, which I guess did come from RECS after all. But blanket insulation isn't the same thing as a "premium" product, especially for gas WHs. For gas, a premium product is a power vent which has a higher RE as well as lower tank losses, not from jacket insulation but from not having an open natural draft flue. I'll look at what's in RECS now that I know to look for the blanket insulation.

In terms of changes, maybe nothing on the electric side (we could rename to indicate it's jacket insulation, and there's also options in options lookup we can change to more directly reflect jacket insulation, but we might want to talk about that first). For the gas side there's separate premium products, so maybe we need a new option that is a gas tank with jacket insulation and then a separate premium option if I can find data for how many premium tanks are out there.