A: You, (and we), really can not afford not to. We as a species have taken this planet to the edge of it's capability to support us. What we need to do is find a way to impact it less. To that regard, it's really as simple as thinking twice before you "use energy", other than your own of course. Ride your bikes or walk if you can. Take public transportation, (the ferry is a blast!). Think ahead and combine your trips. Minimize your trips.

  As far as affordability in the building sector goes, the greatest conservation and efficiency can be achieved through proper site design. By utilizing, or in some cases blocking, the energy that falls or passes through a site naturally, you can greatly reduce a home's energy usage, and your energy bills, with absolutely NO ADDITIONAL COSTS! Proper shading and usage of heat absorbing materials can create an extremely thermally stable interior environment. Proper placement of operable windows and exterior spaces can enhance or block prevailing winds for cooling and ventilation, conversely for warmth. Again, a great many of these principles are purely non-mechanized systems which use virtually no energy to install or maintain. It is a function of the layout and design of a structure.

  If you have an existing structure, the same principles can be used to create shading, ventilation, thermal mass, (which stores and later radiates solar energy), and the like, often  with a minimal amount of remodeling. Insulation is also very important to keep interior temperatures stable. Adding insulation is usually a fairly inexpensive undertaking, and yeilds tremendous savings when combined with the above basic design principles.

  Beyond that, you begin to get into mechanical systems such as photo-voltaics, (solar panels for electrical generation), solar water heating systems, wind turbine electrical generators, hydronic heating, (hot water circulation through building components for heat), and many other methods. Different methods and systems will have greater or lesser benefits depending on site conditions and location. That's why a reputable design professional familiar with the available systems is so important when designing a new structure, or remodeling an older one. For instance. "Solar panels" are not always a viable or cost effective option, such as on a north facing hillside slope.