Research Highlights

Energy Use Patterns in Off-Grid Houses – Case Study #12: Eastern Shore, NS

House Description

A 9.7 x 7.3 m (32 x 24 ft.) one-storey house built on an open crawlspace. The house was built in 1994 and is currently occupied by a single individual, but was previously inhabited by a family of four. The bulk of the glazing is to the south. The N and NW facade of the house are protected by trees, which reduce the rated output of the wind generator. An airtight stove (3 cords wood/yr, one softwood, two hardwood) on the main floor provides space heat.

Thermal Envelope Summary
AC/H@50 Pa: 3.72
Walls: 3.5 RSI (R20)
Ceilings: RSI 5.3 (R30)
Floors: 5.3 (R30)(cats have dislodged some of it)
Windows: thermopane, single hung openers
Doors: steel polyurethane core

System Description

Power is supplied by a 50 W PV panel and a 750 W (rated output) “Wind Baron” wind generator. Energy from these sources is stored in a 600 Ah battery bank and fed to a Trace 800 modified sine wave inverter for large loads. Two “mini-circuits” are also in place for small loads. Each of these consist of a 50 W PV panel connected to a 300 Ah battery bank feeding a 125 W Statpower modified sine wave inverter. The house is wired for 12 VDC and 120 VAC. A 1 kW gas generator supplied backup power until two years ago, it was sold when the load was reduced. The self-installed system cost $5,000 CAD.

System Performance

The 120 VAC load on the system includes lights, TV, battery charger, vacuum, laptop computer, and a cell phone. The 12 VDC load includes a marine water pump, rechargeable power tools,VCR and chest cooler. The total possible daily load is approximately 5.8 MJ (1.6 kWh), while the actual load is estimated to be 2.4 MJ (0.7 kWh). Propane is used for cooking.Water is heated on the stove. Approximately 240 L of propane is used annually.

The actual electrical use in this house is about 820 MJ (230 kWh) annually. The average annual lighting and appliance use for this vintage house in Nova Scotia is 24,500 MJ (6,810 kWh).When the kWh equivalent of the propane use is included, the total load is 6, 510 MJ (1,810 kWh). There is a difference of 17,990 MJ (5,000 kWh), a reduction of 73%. These figures do not include space or water heating (water is heated on the propane stove, but is used only for dishwashing and the occasional shower. The single occupant uses a “solar shower” bag for regular showering).

Notes From Homeowner @ System Operation:

The battery bank has partially failed due to being drained beyond the 50% level, and also because poor quality batteries were purchased. It is important to install the best quality batteries possible, with the longest life cycle noted. Extra cost on the batteries could possibly be counteracted by adhering to the 1% rule (from marine applications) which is: no charge controller is required for the battery bank if the bank is 100x bigger numerically than the 12 V output (in Amps) of your PV array.

Homeowners’ reasons for going off-grid:

Bringing power to the remote location would have cost $30,000.Wanted to create an affordable, energy efficient off-grid house that would allow the owners to enjoy their lives without being in debt or having to work to keep up to operating costs.

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