I recently sold a farm about an hour outside of Philadelphia, PA. I researched about going the self-sufficient route, not off grid, just producing 90% or more of my own energy. I also contemplated buying acreage and building a house. Here's what I found out:
1) Insulation, like reducing your expenses, provides a bigger benefit than increases your power production. I used a combo of spray foam and mineral wool. Spray foam filled in all of the leaks/cracks in the house. Mineral wool provided the cheapest R-value while discouraging rodents.
2) Have more than one source of power. I had a big barn roof & 1/4 acre of south facing land that I planned to put solar panels on. Plus, a small hydro generator from year round creek. And finally, a small wind turbine. Yes these are all costly upfront, but my plan was to stay at the farm for 30+ years. (separation & job relocation caused me to sell after only one year)
3) It is expensive to renovate an existing home, but more costly to build. The cheapest quote I got to build on empty land was $125/sqft. That house was basically a two story box with the cheapest materials possible built by a builder friend who cut me a deal. Also, new construction has to conform with all of the new building codes (water run off plan, electrical codes, septic plans, etc.) while old homes usually are grandfathered in...usually.
4) The smaller a house you can live in the more cost and energy you will save...in all aspects. A family of four can comfortably live in 1500 sqft. or less vs. the common 2000 sqft house. Thats less space you have to clean and maintain (increase in time, personal energy, happiness). Less costly to build or renovate. Less energy to operate & heat/cool.
5) I learned so much from renovating. Plumbing, electrical, tiling, roofing, painting, etc. that now I can tackle almost any project in a home. Life skills...
Just my two cents...