What you save with a tankless is distribution losses (and a little bit of air-conditioning to pump those losses out of the house in summer) . Electric tanks themselves have very low standby losses (far lower than gas-fired tanks). The overall average efficiency is similar in long draws, but in very short hand-washing draws you skip filling a length of pipe with hot water (that then gives up the bulk of the heat to the house over the following hour unless EXTREMELY well insulated.) If all points of use are within 20 feet of the tank it'll be hard to rationalize.

If you go with THREE tankless units you'll have a pretty serious amperage requirements! You might consider one tankless unit (in the kitchen, say) and a tank for laundry/bath, where the draws tend to be bigger/longer on average. But it depends a lot on the layout of the place. Tiny well-insulated point of use 2-6 gallon tanks (Bosch Ariston, etc) can work pretty well for kitchens, bathroom-sinks, etc. too, saving the distribution loss problem with short-draws, with much lower current requirements than a tankless.

Dana1, thank you, I'm trying to send you a private message - let me know if you don't receive it...

Your in the deep south, sun, heat, no freeze issues.
Go solar, SRCC certified 80 gallon electric storage tank, 2 4x8 collectors, pumps and drain down system cost about $3,500.00, plus install labor. Now the whole sum Labor+ materials is 30% credit on your fed taxes, and minimal utility bills for the life of the system (copper panels last about 25 years). Here is a link to programs in your state for additional rebates and tax credits
http://www.dsireusa.org/library/includes/map2.cfm?CurrentPageID=1&State=LA&RE=1&EE=1
Dan

I am totally happy with my Seisco RA 28, It has enough flow to shower, using water from an ice covered lake in winter. No, I can't do more than one thing at the same time, in winter! I used a 125 amp breaker in the main panel (megabucks vs 100 amp breaker) and would downsize (for my needs) 'the next time'.

Point of use and tankless are separate concepts.

Electric tankless saves a little bit of heat loss from the tank but requires a lot of amps and might have more scaling issues.