Fundamentals of Resilient Design: Backup Power for Homes

Posted by on Feb 7, 2017

Group-net-metered solar array on our 1812 barn at Leonard Farm. We don’t have battery back-up, but we have an inverter that allows us to pull daytime power off the array even when the power grid is down. Photo: Alex Wilson

We lost power again the other day. It wasn’t a big problem, but once again, it reminded me how dependent we are on that electrical current coursing through our overhead power lines. In our case, we lost power even though our home is net-zero-energy, meaning that we generate onsite all of the energy we consume on an annual basis—we even have enough left-over solar electricity to power our plug-in electric-hybrid Chevy Volt.

But living in a solar-powered, net-zero-energy, net-metered house doesn’t solve the problem of being without power when the grid goes down—which can happen for any number of reasons, from a tree falling over a power line to an equipment malfunction hundreds or even thousands of miles away, to an earthquake.

So what are our options for providing back-up power in homes?

The table below (also available as a download: Backup Power Options for Houses) presents a fairly comprehensive range of options for backup/emergency power. There are some others, but these represent the vast majority of solutions you will come across. With each option, the main features are described, followed by pros and cons, and special notes. Note that one of these options isn’t quite ready for prime-time, but still offers huge promise.

For commercial buildings and groups of buildings, other backup power options exist, including combined heat and power (CHP) systems and microgrids. Those options are not covered here.

 

5 Comments

  1. Good work, & thank you very much! Per last option above, +-$400 got me an installed quick connect plug to my standard Prius’ starter battery and a $200 pure sine wave 1000 W AIMS inverter. So far it’s worked well as an easy to use, inexpensive backup; longest outage so far +-4 hrs. Calculations suggest a full tank of gas would keep our freezer and refrigerator cold (with periodic support), our phones, PC’s and a few lights running for 40+ waking hours, likely more. And yes, the car’s engine only turns on when the starter battery gets low.

    • I checked at my local Chevy dealership, and the expert in EVs there said that Chevy has said it cause problems with the delicate electronics—though he also said that it would be pretty easy to do. I would love to find someone at GM I could talk with about this. I think the company should integrate this feature into their cars and promote it. We have a 2016 Chevy Volt.

  2. Alex,

    I was surprised to see your comment on portable generators. We have one which plugs into a dedicated outdoor connection linked to certain critical circuits in the house–refrigerator, freezer, wood furnace blower, pump, etc. This was installed by a licensed electrician so I presume safe and within code.

    • Greg, good to know. Thanks for the correction. I’ve updated the table.

  3. We are fortunate to have natural gas, which we use for cooking as well as supplemental heat (gas logs). I assume that in the event of an extended power outage of weeks or months that at some point we would lose access to the natural gas as well. Is this correct?

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