I think you are too worried. I was before I bought a PHEV. Battery Failure rate for 2nd generation Prius is 1/1000 at 200,000 miles. I think it is 1/3000 in 3rd generation . Depending on how much you drive you save a lot of money with the hybrid or phev. We drive about 18k per year so a lot. Our fuel savings on year 1 with a clarity phev was $1972 (measured, not just calculated). Cost on vehicle after government rebate was $26500 for touring edition. Hence after 14 years best case scenario, the car will be free and then $1500+ extra savings per year. Batteries globally are warrantied for 8y/100k miles. California compliant states are 10y/150k(which we live in). Worse case scenario we have a 1/1000 lemon. Battery dies at 160k. We replace and go another 150k for $6k. Still better than gas. Or battery slowly degrades and at 250k I am driving gas only with battery holding 20% getting 40 mpg. Most modern car batteries degrade to about 90% capacity and then lose about 1%/yr. (I think a lot of people worry because the 1st generation leaf batteries weren’t cooled and died about 5 years in. We also bought a used 2nd gen leaf after our clarity. 2015, 60k miles, battery is 92% state of health. Should easily last at least 200k miles before replacing battery.) plus don’t forget other savings. No oil changes. No radiator upkeep. B/c > 50% of breaking is with magnets, haven’t even had to replace brakes Yet and last inspection a year ago they said >80% left (on the 60k miles leaf)