Would you spend the extra $2k on the 12kPV for a garage system?

First pin down what “not grid-tied” means for your setup. If you want a standalone system with no utility connection, the 12000XP seems like the more direct fit. If you want the utility available to support loads or charge batteries, compare the 12kPV’s grid functions with what you actually need. Paying extra for features you won’t use is hard to justify.

Check the current manuals and warranty terms for both exact models before deciding. Product details and availability can change.

I wouldn’t treat the longer warranty as a guarantee that your lights stay on. A warranty may help with repair or replacement costs, but it doesn’t necessarily mean a quick replacement if the inverter fails. Another battery gives you more stored energy, not backup inverter capacity, so those solve different problems.

If keeping critical loads running is the priority, think through what happens during an inverter outage, including whether you can temporarily supply those loads another way. Then compare the warranty coverage and likely replacement process against the extra battery’s value for your expected use.

For a garage install, I’d also compare the installation requirements, not just the price. One model may have more exposed fan openings, while the other may be more enclosed, so dust, ventilation, clearances, and temperature could matter. Check the current installation documents rather than relying on a general comparison.

My quick read is: standalone system, lean toward the 12000XP if its specs cover your loads. Want utility support or other hybrid features, then the 12kPV may be worth considering. Either way, confirm the surge needs of your loads and the exact warranty terms first.