A 6.1 x 9.1 m (20 x 30 ft.) one-storey house built on an open crawlspace. This house has been occupied by a family of four full-time since the fall of 1997. The house has reasonable solar access. An airtight woodstove provides space heating for the whole house (4 cords wood/year).
|Thermal Envelope Summary|
|AC/H@50 Pa: 13.22
Walls: 3.5 RSI (R20)
Ceilings: RSI 3.5 (R20)
Floors: RSI 4.2 (R24)
Windows: single pane wood sliders w/storms
Doors: steel polyurethane core & wood
The power is supplied by a 420 W output PV array (4-105 W panels). Energy is stored in 8, 6 V golf cart batteries, wired to produce 12 VDC (880 Ah). All lighting is 12 V. A 250 W Trace Statpower inverter produces 120 VAC for the house. A 3.5 kW gas generator provides backup power. The system cost approximately $5,000 CAD.
The load on the system includes 12 VDC lights, a water pump. The inverter powers a 13” TV, a VCR and a stereo. The total possible daily load is approximately 5 MJ (2 kWh), while the actual load is estimated to be 4 MJ (1 kWh).Water heat and cooking is provided by propane. Approximately 1,490 L of propane are required each year. The generator is run from five to 60 hours/month, for an estimated total of 365 hours/year. There is no fridge.
The actual electrical use in this house is about 1,340 MJ (370 kWh) annually. When the kWh equivalent for propane water heating is included, the total load is 24,140 MJ (6,710 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 a further 24,500 MJ (6,810 kWh) for a total of 49,000 MJ (13,610 kWh). There is a difference of 24,860 MJ (6,910 kWh), for a reduction of 51%, without a refrigerator. These figures do not include space heating.
Homeowners’ reasons for going off-grid:
One of the owners is a seasonal worker, and wanted a house that would allow the family to have minimal annual costs, to be able to “coast” through the winter months when minimal income would be coming in. The cost of grid connection was a factor as well. Not wanting to give money to the utility company played a part in the decision.