There are many variables which effect the percentage of savings of a "Green" home vs. a "Regular" home.In all cases it boils down to proper design and integration of systems, construction techniques, region and goals.
There are several factors which need to be considered when assessing savings and they are:
- Material and labor costs for initial istallation;
- Life Cycle costs for up keep and operation;
- Return on investment.
In a properly design system the goal is to minimize the amount of time (years) for the return on investment(ROI). Factors such as government grants, incentives and buy back programs will reduce this time needed period.
60% reduction in energy costs
Here is an example of how I am achieving a 60% savings on energy costs for a current renovation project.
Project: Renovation and expansion of an existing 1959 ranch home in Southeastern Michigan.
Envelope: 45% reduction of heat gain/loss.Construct a high performance envelope exceeding local energy codes by 20% and incorporate rainscreen exterior facade design to minimize thermal bridging. Incorporate natural daylighting and proper shading to reduce electric light usage and thermal heat gain.
HVAC: Changing from gas and electric to geo-thermal resulted in a 66% savings on energy bills. Incorporate geo-thermal heating and cooling and design (2) solar passive cooling towners operated by a program logic controller for ease of operation.
Electric: Design a photovoltaic panel system to off set cost of operation of geo-thermal system.
After the ROI has been met in 5-7 years, the operation of the HVAC system will be completely offset by the production of electricity.
From $1800 to $600 annually
Energy speaking only...the home outllined above has used $1,800.00 annually for gas and electric. After the ROI period the anticipated energy cost wll be approximately $600.00 or saving roughly 66% annually.
Now keep in mind, this does not take into account the cost of renovations and high performance envelope. For new construction expect to pay 10% more in construction costs to acheive a high performance envelope.
In closing, implimentation of only one part of the equation will not result in meeting your goals for energy savings. You must take all parts into consideration so design macroscopic vs. microscopic.
For more information:
Read "How much energy savings do you get by turning a thermostat down 5 degrees rather than turning it off completely twice a day on a timer?" a Q&A answered by David Willson.