If you MUST stick with electric and are willing to spend the bucks add
a high capacity electric tankless in series with and immediately
before the regular electric tank.

It bwouldnt cost any more to heat your water but give you much greater
capacity.

however how old is your existing electric tank? did it ever do the
job? live where incoming water temp is very low given deep freeze
country is currentlyn in.

you could have a sediment filled tank, a bad heater, or incoming water
temp may be lower than normal.