Most recipes tend to be very specific whether you need to finish the
stew in the oven or the stove-top. It probably depends on the amound of
liquid that's desirable, the type of meat and possibly some of the
other ingredients. More "liquidy" recipes are meant for the stove-top
while the more "meaty" ones for the oven (what a gross and vague
generalization). I guess you will have to tell us what kind of stew are
you making. Some stews are also meant for earthenware dishes which you
cannot put on the stovetop. Finally, I'll leave it up to the scientists
but it seems to me that using you kitchen appliances to heat up your
home is very inefficient in any form. Whatever heating you have in the
house will probably do a better\cheaper job. So if heat escapes from
the oven (say you leave the oven door open) it is not compensated by
the lower workload of the heater. Even as high as oil\gas prices are,
your heater is still much cheaper.