Both standard electric and propane are very expensive to operate.

If it's in the basement, utility room, or garage consider a hybrid electric water heater.

There are significant rebates available to offset the higher cost of the hybrid electric water heaters.

After researching tank-type water heaters, I replaced my old one with a plain-old Rheem Performance 40 gallon water heater. Note that Rheem has several models with various features, power requirements, and warranties.

Yeah, hybrid water heaters are available. But they make noise (my water heater is in a closet next to a bedroom) and are expensive. For example, at Home Depot the Rheem XE40T10H45U0 40 gallon hybrid is $1672 while Rheem XE40M06ST45U1 40 gallon standard is $439. But the hybrids are much more efficient (see Energy Guides linked to the web pages above) though their compressors emit cold air into their surroundings. (With only two people in the house you may not actually use much hot water.)