Research Highlights

Energy Use Patterns in Off-Grid Houses – Case Study #8: Antigonish County, NS

House Description

A 6.7 x 10.4 m (22 x 34 ft.) 2 1/2 storey house built on a combination basement/open crawlspace foundation. This house has been occupied by a family of five (now six) full-time since 1994. The house has reasonable SE to S solar access (concession to the view to the SE) and good protection to the north from a treed hillside. An airtight woodstove provides space heating for the whole house (4 cords wood/year). The original part of the house was constructed in 1988 as a seasonal residence, with a typical “cottage” PV system. In 1994, when the family moved in, the house and the system were as described below.

Thermal Envelope Summary
AC/H@50 Pa: 11.24 (one bedroom and loft area not finished)
Walls: 3.5 RSI (R20), double wall construction in progress to upgrade
Ceilings: RSI 4.9 (R28)
Floors: RSI 3.5 (R20)
Windows: double pane
Doors: steel polyurethane core

System Description

The power is supplied by a 420 W output PV array (4-105 W panels). Energy is stored in 6, 6 V L-16 batteries, wired to produce 12 VDC (1,400 Ah). All lighting is 12 V, including compact fluorescent, halogen and hi/low car taillight type. A Trace square wave inverter produces 120 VAC for certain appliances (washing machine, battery charger, skilsaw). A 6 kW gas generator provides backup power. The system cost approximately $10,000 CAD.

System Performance

The load on the system includes 12 VDC lights, a water pump, TV/VCR and three “personal” stereos. Small kitchen appliances run off the inverter: blender, food processor as well as a computer and a household stereo. The total possible daily load is approximately 10 MJ (2.7 kWh), while the actual load is estimated to be 6 MJ (1.7 kWh). Propane fires an instantaneous (demand) water heater and the range. Approximately 1,700 L of propane are required each year.The generator is run approximately six hours/week during November and December, and two hours/week through January and February, for a total of about 64 hours/year. There is no fridge, but a chest cooler is situated in the basement. The cooler sometimes requires ice to keep the temperature down during July and August.

The actual electrical use in this house is about 2,160 MJ (600 kWh) annually. The kWh equivalent of the propane appliances and water heater is 38,960 MJ (10,820 kWh), for a total of 41,120 MJ (11,420 kWh). The average annual lighting and appliance use for this vintage house in Nova Scotia is 24,500 MJ (6,810 kWh).Water heating accounts for another 24,500 MJ (6,810 kWh) for a total of 49,000 MJ (13,620 kWh). There is a difference of 7,880 MJ (2,190 kWh), a reduction of 16%, without a refrigerator. These figures do not include space heating.

Notes From Homeowner @ System Operation:

The house is primarily wired for DC, using a “modified buss bar”. Large DC cables run up to the second floor through a concrete chase and travel to outlets on short runs of smaller wires. There are four AC runs throughout the house. Fuel usage should decrease as two new panels were installed this year, and two more will be installed next year, for a total system output of 720 W.

Homeowner’s reasons for going off-grid:

PV installations are a part of the homeowner’s business. PV is virtually maintenance free (requires someone to sweep snow off the array, turn the panels occasionally, and turn the inverter on or off), making it easy for non-technical members of the family to live with the system. The house began as a low-use seasonal dwelling and kept being added on to until it became a full-fledged dwelling.

Homeowner’s observations on living off-grid and energy use patterns: