Not sure where you are exactly, but in Sunny California (and many other places) an investment in a Solar PV system is not only a tax free investment of your hard earned cash but the value off appreciation is equal to the savings in energy the first year times 20! For example: $30K Solar investment (20K after Federal Tax Credit) saves $4K the first year in service. $4K*20yr=$80K in tax free property value appreciation. The best part is you get your return weather you stay or sell! The increasing cost of power from the power companies compounds return even more with a more levelized $/kWh. Other investments that potential buyers may be looking for could be retro insulation, efficient HVAC upgrades, or windows.