For accumulating statistics of power-on hours, number of power failures, generator hours.

Mechanical, “odometer” style – can be read without being powered up, no battery to eventually fail (but maybe 10 years is long enough?)

• ENM T51E1, 240VAC, 50/60Hz, mechanical
• https://catalog.enmco.com/item/enm-counting-instruments-hour-meters/t51-quartz-ac-hour-meter-i-/t51e1
  • https://www.grainger.com/product/ENM-Hour-Meter-6-Digits-2PAN8, $33 (screw mtg)
  • https://www.grainger.com/product/ENM-Hour-Meter-6-Digits-2PAN9, $29 (flush mtg)

AC hour meter, ENM, 230V, in-stock:

• https://us.rs-online.com/timers/digital-timers-hour-meters/?a10=ENM%20Company&a7=In%20Stock%20Only&n8819=5-250%20VAC/VDC,85-265%20VAC/90-360%20VDC,115-275%20VAC/115-275%20VDC,230%20VAC
  • Lots of options in that link; I tend to lean towards mechanical because they can be read without being energized, and the ones with permanent batteries are limited to a decade or so. Maybe that's long enough!?

Mechanical counters with 230V input are difficult to find in stock.
These are all self-powered with at least 10year battery and differ only in the mounting method:

• https://us.rs-online.com/product/enm-company/l3fa/70901122/ $30
• https://us.rs-online.com/product/enm-company/l3fb/70901123/ $33
• https://us.rs-online.com/product/enm-company/l3aa03/71254881/ $31 (round)
• Data sheet: https://catalog.enmco.com/Asset/709.PDF