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In depth
| 11/23/17

Want to go off-grid? You might need 100s of Tesla batteries


Going completely off-grid is infeasible for most households in Western Canada, energy systems modellers conclude, due to the diminished amount of sun in our northern latitude. To “cut the cables” to the electricity grid, requires an impractical number of batteries or solar panels.

Families in BC use solar panels on their roof and install batteries in their garage because they want to reduce electricity costs or do their part to help reduce emissions. Some have dreams of one day going entirely off-grid. So researchers with the Pacific Institute for Climate Solutions’ 2060 energy future pathways project modelled just how feasible this would be.

They used 2016 data from a typical three-bedroom house in Victoria with an annual load—or average electricity demand—of 9,600 kilowatt hour (kWh). The house uses natural gas for its heating and a conventional gasoline vehicle, meaning no extra load from these sources.

A common PV system is 12 kilowatts (kW) as a larger PV system requires more roof. Researchers found that given Victoria’s solar irradiance, a 12 kW PV system needs a 1,766 kWh battery to achieve self-sufficiency. This is equivalent to 131 Tesla Powerwalls.

Another option is to reduce the size of battery and buy a larger PV system, as more energy is available and thus less needs to be stored. If a homeowner bought a 30-kW PV system, they could get away with a 289 kWh battery (equivalent to 21 Powerwalls). But this PV system would require an area of roughly 300 square metres (3,200 square feet)—about the size of a tennis court.

They ran the numbers for Vancouver, Kelowna and Calgary. The results for Vancouver and Kelowna similar to Victoria. But Calgary, with its clearer winters, required less PV and battery capacity to be self-sufficient. Calgarians could make do with a 9 kW PV system and about 62 Powerwalls. With a 30 kW PV system, taking up 240 m2 (2,475 square feet), the homeowner needs roughly 10 Powerwalls.

But in these clear, cold places, the electricity demand of the household rises due to the electrification of heating and transport so the prospect of self-sufficiency is even further out of reach. The researchers found that the increase in demand from heating via electric baseboards at least a 22 kW PV system and 236 Powerwalls. Newer technologies, such as heat pumps would have a reduced impact on electricity demand.

The projections for the number of batteries seem mind-boggling, but they are in line with storage requirement assessments for other jurisdictions. Researchers also stressed that consumers should factor the carbon footprint of their electricity sources. For example, if you switch to solar from low greenhouse gas (GHG) emitting hydropower there would be no reduction in GHGs and perhaps even an increase, as electricity from rooftop PV is more GHG-intensive. But switching from GHG-intensive, coal-fired electric to solar would achieve a marked reduction.

None of this is to say that rooftop solar has no place in our suite of energy options for the clean transition. But it does suggest that for western Canada at least, the challenge for ordinary households remains substantial.

In depth

Exploring Climate Policy Options: A Conversation with Mark Jaccard

Energy economist Mark Jaccard helped design BC’s carbon tax, and he still supports it. But he questions just how politically viable a stringent tax—at the level needed to meet climate targets—can really be. So he also continues to explore how other policies that the public find more acceptable could work.

Climate news and analysis that's relevant for you, every week.