November 09, 2009
| by Steven Castle
Want a “net-zero” home that produces all of its own electricity? No problem. You just estimate how much energy you’ll use, then buy enough solar panels to produce all the electricity for your needs, right?
If there’s some energy-efficient home technology, like a home control system that shuts things off and some lighting control, even better.
But what if, say, you worked backwards on that as did Jabar McKellar of Envision Solution in Dublin, Calif. McKellar designed a system in this 4,300-square-foot home, in which the solar array is sized to the energy savings in the house.
“Basically, I sized the solar array in conjunction with the automation system,” McKellar says. “I compiled estimated energy usage from each of the home’s subsystems and assisted the owner in choosing the most efficient appliances.
Using a HomeLogic control system that could automatically turn things on and off, McKellar shaved energy consumption in the climate, lighting and audio/video systems.
“By reducing energy costs by approximately 30 percent, I drastically reduced the overall size of the solar array,” McKellar says. Instead of a 7-kilowatt (kW), 44-panel solar array normally needed for a house this size to achieve “net-zero,” the house only required a 4.1-kw array of 27 panels, saving the owner about $17,000 in costs—and lots more in energy efficiency down the road.
Some of things McKellar did are great ideas for anyone building or retrofitting for energy efficiency:
- No lights ever come on past 90 percent. This saves 10 percent in electricity and doubles the life of the bulb.
- Lighting touchpads are eliminated from most zones, forcing the occupants to use the HomeLogic in-wall touchpanels to enact energy-saving scenes.
- Motion sensors and timers are used on all lights not on the lighting control system. For example, a closet has a manual switch that shuts off the lights automatically in five minutes.
- When the owner goes out or to bed, the house stays in an away mode that cuts all power to the audio/video components that draw standby or vampire power. Only security cameras and the audio/video distribution system are left in standby, so he can view the cameras.
- The HomeLogic system provides an “event viewer” for the dual HVAC systems, which gives real-time information on the amount of energy the homeowners are using.
- In the first 20 minutes of cooling the home, ceiling fans come on to circulate the air and reduce the need for air conditioning.
- Heat from the equipment rack is exhausted outside in the summer and recirculated in the home in the winter.
With federal and state incentives, the energy-saving automation system and downsized solar system in this home cost the homeowners as much as a larger solar array they didn’t need (based on a 3,000 to 3,800 square foot home). So here are some stats and costs to help you decide if energy-saving automation is worth it:
COST OF GOING ‘NET ZERO’ WITH SOLAR ONLY (NO AUTOMATION):
7-kilowatt grid-tied solar system: $64,000 (approx.)
Approx. rebate PG&E/CSI (Calif. Solar Initiative): $8,894
Federal gov’t rebates: $19,200
After rebates: $35,906
COST OF GOING ‘NET ZERO’ WITH SOLAR AND AUTOMATION:
Automated lighting (15% energy savings): $9,000
Automated climate (20% energy savings): $3,000
Automated phantom-load shut-off (10% energy savings): $3,000
Energy-efficiency engineering (5-20% savings): $2,000
4.1-kw grid-tied solar array: $40,050
Fed gov’t rebates: $12,150
CSI (Calif. Solar Initiative): $6,003
Additional PG&E & federal government rebates: $1,900
Cost of Downsized Solar with rebates and automation: $36,997
Steven Castle is Electronic House's managing editor. he has been writing about consumer electronics, homes and energy efficiency topics for two decades. He is also the co-founder of GreenTech Advocates