120V HPWHs don't have backup elements, right? Note the new BackupHeatingCapacity element added in hpxmlwg/hpxml#361. We should probably allow it as an optional input for any HPWH, default it appropriately in hpxml_defaults.rb when not provided, and set to zero for a 120V HPWH.

Performance Maps for 120 V HPWHs:

These are largely consistent with the 240 V HPWH performance map, which it should be: it's the same refrigerant/cycle, just smaller.

Also worth mentioning: this is the shared circuit version of the Rheem 120 V HPWH. Rheem also offers a dedicated circuit version that has a much higher capacity. The max current on the shared circuit is 7.5 A (900 W input) and 12 A for the dedicated version (1080 W input).

We now have models of both shared and dedicated circuit versions of Rheem's 120V HPWH. There's still some cleanup to do for making sure all tests pass to get this merged in, but it can successfully work with ResStock, and now that that's ready I'm planning to go back and try to address those lingering issues (like homes that have multiple WHs) for both the unmet loads program and the 120V HPWH.

On the HPXML side, we'll have to make a couple of updates:

• Some way to denote a 120V vs. 240V HPWH
• A way to model tempering valves, and specify separate setpoints for the tank and the tempering valve.

We'll also have to decide if we want to include/support 120V products that have backup elements, like the AO Smith (but NOT the Rheem, which is the focus up until now).

Here's some results from a recent midsize (30,000 sample) run: