of course they will. how much? it depends.

if you single pane windows are liek my single pane windows, then it certainly must help. mine are so bad that you feel teh cold/heat a couple feet away. not drafty, just single pane metal frame that conducts heat/cold big time.

You will likely see some savings but generally the ROI on window replacement is MUCH less than doing many other cheaper things first. A bigger bang for the buck is found in decreasing order by doing through airsealing/draftblocking of attic and basement penetrations and bypasses; adding attic insulation if needed; wall insulation especially kneewall issues if they exist; hvac upgrades; last and most expensive (and least return on your money)are the new windows. You might look into doing something cheaper if you are dead set on the windows like getting some storms for them. That is probably alot cheaper and just as effective as the new windows, but by all means do the other things i listed first if neccessary. Any installer that says you are gonna save 20-30% or more with new windows is full of it.

Well my insurance is paying for the new windows so it is no big deal. Woke up this morning and it was 40 deg outside and the window frame inside the house was 42 deg and sweating ( i used a temp gun ). If they are allowing cold and heat to transfer this easily then I shouild see some energy savings.

No one disputes that you will see some savings; the only question is how much. I say not much at all but you might be more comfortable with them. How high are your energy bills right now? The biggest actual energy savings are gained in the cheaper easier to do items i mentioned above. good luck.

My home is 2200 sq ft w/ gas water htr, dryer, stove, and furnace. East west orientation with 44 windows. summertime energy bill is 350 to 400 and winter is 150 to 200 while nat gas is 100 to 200. Live in South Texas.

well, then realistically you probably won't see major savings. but over the long run they will pay themselves in 10-15 years.

my house is 2400 sq ft, E/W orientation, and a couple dozen windows with 12 of them being 3'x6' or larger. my first thing was to replace the old manual tstats with set backs, then a couple years later the oldest of my 2 central HVAC systems. these 2 things alone dropped my energy usage from a little over 5000kwh a month avg with peaks around 61-6200kwh, down to below 4000kwh peak and avg less than 2500kwh. we use heavy curtains on teh windows to help insulate them for now, and as i get the money i will replace them. but i also need a new roof, 1 septic field is getting ready to require replacement, house needs painting, etc and etc ad nauseum!