I encourage you not to over-estimate your needs. I have COPD and asthma, so I tire much more easily than I once did. I use my bike often for laundry, groceries, and basic transportation. I bought the cheapest e-bike I could (36 volts, 8 amp hours, 250 watt motor) for financial reasons, and worried that it wouldn't be enough. So far, I've had the e-bike about 20 months and never needed more. I'll note that I ride slowly (10 mph in all conditions), as I always have, and I only use the low assist mode.