Energy usage has fallen dramatically, by 62%, after the retrofit by Recurve (formerly Sustainable Spaces).  The significant reduction in energy usage occurred even with the installation of air conditioning in the house.

Energy usage pre- and post-retrofit

Energy usage: pre-retrofit, and post-retrofit, actual and budgeted.

Recurve’s budgeted energy usage for the house is extremely close to the actual energy use.  Over the five month period, the net difference in the budgeted energy  usage of 5,263 kWh and the actual energy usage of 5,221 kWh is only 42 kWh, less than 1%.

It shows that current normal comfortable behavior is compatible with a net zero energy and carbon neutral design.  The home owner can be confident that energy bills won’t go up, and can plan for future increases in electrical demands by adding on renewable production in the amount of the new demand.  For example, planning for a plug in hybrid.

During the first five months since the retrofit, the heating load has fallen nearly 46% (56,000 BTU/h to 30,000 BTU/h) and the cooling load has dropped 17% (27,000 BTU/h to 22,500 BTU/h).  The total retrofit energy reduction is 62%.

The energy that was needed was purchased from PaloAltoGreen, the utilities renewable energy program.  Photovoltaic panels were installed in November 2009.  Energy from that point forward is provided by the panels on-site and the purchased renewable energy.

Piechart of the energy usage after the retrofit

The pie chart graphs the energy distribution. HVAC and Domestic Hot Water Systems consume most of the energy in a typical single-family home.   High-performance insulation and the heat pump have shifted the load primarily to “Others”.  This shows the efficiency of the insulated envelope and the heat pump’s reverse cycle chiller.