March Q&A for New Homes

What’s the average size of a residential solar electric system?

The average solar electric system in Oregon is about four or five kilowatts. How many panels is that? Most panels installed in 2014 were about 250 watts each. A five-kilowatt (5,000-watt) system would consist of about 20 panels. A four- to five-kilowatt system will generate more than half of the average household’s electricity usage over the course of a year—though more is generated in the summer than in the winter. Remember, if it is an all-electric home, the average electricity usage might be higher.

How many indoor heads do I need to install with a ductless heat pump?

The number of indoor heads needed to install with a ductless heat pump ultimately comes down to the heat load of the house. At a minimum, you want to install one per floor. A wall unit in the main living area is sufficient for a well-insulated house with a ceiling cassette in an upstairs hallway. If the house has any rooms that are surrounded by unconditioned spaces on five surfaces (such as a bonus room), you will want to consider additional heat sources for those zones.

For verifiers: What if the water heater my builder installed isn’t listed on the AHRI website?

Occasionally we’ll see equipment that hasn’t been third-party tested for efficiency claims. When that happens, we can still model the equipment by de-rating the manufacturer-claimed efficiency by 5 percent. When modeling the home, select or create an entry in REM/Rate™ with the appropriate details. Make sure to add a note entry that includes the original rating and that you’ve de-rated the equipment because it wasn’t listed on AHRI. Make sure to include the model number of the water heater in the Axis Checklist so that we can verify the efficiency.