I purchased a 1958 3br 2ba ranch in Northern NJ nearly two years ago and have been working on improving the overall efficiency of the home.  The baseline blower door reading was 5785 CFM50... after extensive air sealing and insulating (of which we had none in our walls) the reading is now 1750 CFM50.

I currently have oil heat (baseboard hot water) with an indirect hot water tank, however, our neighborhood now has natural gas, so I had the service ran to our house.  The current boiler is about 23 years old, but is running at 86.5% efficiency per its last service.  The indirect tank is about 10 years old.  Both are located in finished climate controlled basement that is partially above and below grade due to the sloping of the property.

A central AC system was added to the home, and only to the upstairs, about 8-10 years ago.

The windows are the original single pane wood framed windows.  Storm windows were added about 15 years+ ago.  The doors are all wood and are the originals to the home.

I am not sure what project to tackle next.

1. Replace the windows and doors (Likely 3 pane Intus windows)
2. Replace the boiler with a ModCon (Likely Viessmann or Triangletube) and the hot water heater (tankless, nat gas, heat pump)
3. Replace the retro fit 10 year old AC system with something with a higher SEER rating

I tend to think it would be best to complete the insulating and air sealing before I address the boiler and AC system so the system can be sized with an accurate heat loss reading.

The 12 month oil usage before the insulating and air sealing was 1,100 gallons

The 12 month electric usage before the insulating and air sealing was an average of 900kwh mo with spikes of about 1300-1600 during the summer months.

We have a newborn at home any my wife insists we keep the home a constant 70 degrees year round.

I currently only have the funds to do one of the three projects.

I would appreciate your input/guidance/direction

 

I think step 0 - put your house data into a modeling program (such as BEopt).

I have been trying, without success, to find someone that can assist me with this in my area. I have contacted a number of energy auditors in my area that seem to do nothing more then walk around and point out old things that should be replaced. I have had one that actually did some basic modeling, but nothing by any means that detailed or involved.

I have been looking for software to try the modeling my self and wasn't aware of any free/good options. I will have to give BEopt a try.

First, congratulations on your air-tightening success! Getting it under 2000cfm/50 is pretty good, and I'm sure it's something you can FEEL.  (But never stop fixing air leaks as you find them!)

If you're on a natural gas main replacing the boiler with a mod-con will be cost effective.  If propane it might be too, but only if the existing boiler is very oversized for the design condition heat load (like more than 4x, which it might be now that you've tightened up and insulated.)

In NJ replacing the AC with a best-in-class variable speed compressor & air handler heat pump with an HSPF of 9+ would be a more cost effective way to heat than with oil or propane, and may come close to competing with natural gas.  The modulating variable speed systems are QUITE comfortable during the heating season despite somewhat tepid exit air due to the low-velocity of the air handler.

If you have decently tight windows & storms (they must be at least sorta tight to hit 1750cfm/50) the cost effectiveness of replacing them with triple-panes may have an extremely long ROI in your climate, but can effect comfort.

I assume you've replaced all of the lighting with high-efficiency types.  So...

First, do a Manual-J heating/cooling load calculation, then take a serious look at the heat pump option, since that's likely to have biggest bang/buck on heating & cooling costs and if it replaces the function of the boiler you can mothball the boiler and put in a heat-pump water heater.  

Short of a Manual-J you can get a pretty good estimate on the heat load using I=B=R methods with any spreadsheet tool.  (Which I can explain in greater detail if you like, but I'd need a better description of the construction type/siding and insulation levels, as well as a ZIP code to determine a reasonable outside design temp.)