• John Sutter

Power Your House With Your Car?

Bidirectional charging coming soon to a home near you.


Currently there are approximately 400 thousand all electric vehicles (“EV’s”) in the PG&E service area. The newest of these cars have batteries that can hold up to 100 kilowatt-hours of electricity (“kWh”), enough to power an average California household for nearly a week, and with judicious use, even longer. My 2017 Chevy Bolt’s battery stores 66 kWh’s. In comparison, two fully charged Tesla Power Walls, costing about $25 thousand dollars installed, has available about 25 kwh when fully charged. If you have a fully charged EV sitting in your garage, why not tap some of this energy in a power emergency? All this potential stored energy could be fed back into a home’s electrical system. It's called bidirectional charging, or vehicle to grid (“V2G”) charging.

California policy makers and solar inverter makers are seriously looking at mainge EV batteries a viable source of power for home owners and even the power grid. The idea is as simple as it is genius: The high-voltage battery of an EV is charged via the wall plug at home, but can also feed supply energy back to the house during a power emergency. While simple in theory though, the concept requires a high level of technical intelligence and coordinated interaction between different technical components. Most knowledgeable observers believe true commercial adoption bidirection charging is still two to three years away, but none doubt its eventual widespread adoption.


Time of use pricing for electricity use is coming to most of California in the next year or so. An intriguing possibility for property owners with a photovoltaic generation system is to have their electric car provide it’s stored domestically solar generated clean electricity when the sun is no longer shining. Thus the vehicle could supply the stored daytime electricity back to the house for late afternoon and early evening use when electricity will be the most expensive. The car would then recharge in the late nighttime hours when electricity will be the least expensive.


Earlier this year, Southern California Edison launched a demonstration project that allows EV batteries both to charge and to discharge power onto the grid while they are plugged in, the same way stationary batteries do. Much of this research is being funded through California’s Electric Program Investment Charge- or EPIC, which manages an annual budget of $13 million for demonstrations to further grid advancements that will help meet the California’s energy and climate goals.


The technology to make these exciting concepts a reality is in the late developmental stages, but there are still hurdles to overcome before Californians be able to tap the energy stored in EV batteries in safe, reliable and efficient manner. The key word of course is safe. Any time you talk about electrical power at this level, safe operation is a key. There is other design and testing still to be done before V2G can be rolled out, for example the standardizing of equipment that will allow interconnection between electrical system components possible.

These are exciting and challenging times for us energy geeks, as we watch and push technology as we attempt to slow down environmental degradation before our world loses it capacity to support it’s 8 billion and still growing number of human inhabitants .


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