Tiers without a maximum kWh greater than the kWh consumed give negative bill savings with net billing

[brtietz]

Describe the bug

Changing a max tier from 1e38 to 100 in the default commercial model leads to negative bill savings with net billing

To Reproduce

Steps to reproduce the behavior:

1. Load a behind the meter model
2. Set the compensation for distributed generation to net billing
3. Set a maximum tier to 100 kWh (or something lower than the month's usage
4. Run simulation
5. The bill savings are negative

Expected behavior

The utility rates module should throw an error in this situation, as the maximum tier is unspecified.

Screenshots

Rate table that causes the error:

Bogus bill savings:

Operating System and Version

• OS: Windows
• Version: Patch candidate 2023.12.17r2

Additional context

I'm fine with deferring this to the release, as it falls more into the category of "better handling of user errors" and is not a bug with a valid utility rate

[brtietz]

From 9/25 SAM meeting: every period should have a tier with infinite usage. 1e38 comes from floats: possible need to switch to inf in the UI (separate issue).