What would these investments go toward? Well, there are some options in PNM's draft 20-year plan aka "Integrated Resource Plan" – https://www.pnm.com/2026-irp
Page 6 of their “statement of need” talks about power sources that can run all the time without stopping (this is called "firm dispatchable" power).
That list includes:
Long-duration energy storage – batteries and facilities that can store energy for more than 16 hours (this would also be good for wind/solar assets)