Those old plasma TVs are energy hogs -- around 200 watts more for your size TV.
As for savings, well that depends how many hours a day it is used. Our guest room has such a Plasma as yours, but it might get an hour of use a month. I don't sweat the extra 200 Wh

And it makes a lot more sense to take the money I could have spent on an efficient TV and spend it on extra PV instead.
Some Arithmetic
Say a replacement costs $500, or you can take the money and buy 500 watts of PV
The PV gives you ~ 2500 Wh a day of clean energy
If the Plasma is consuming 250 watts, then break-even is 10 hours of Plasma TV use a day