House Electric Backup during Grid Outages

L. David Roper
21 November, 2017


It is prudent for home owners to plan for possible electric-grid outages of short and long duration. This document is a discussion is about planning for such grid outages.

Simple Things to Do

There are several web pages about simple things to do to prepare for grid outages at the house level:

Community Considerations

There are several web pages about community preparation and response to grid outages:

House Battery Backup Systems

To reduce global warming battery backup should be used instead of generators that run on fossil fuels.

Appliance and Home electricity Energy Use

Tesla Powerwall Battery for Grid Backup

Can be set on floor against wall or mounted on wall indoors or outdoors. Dimensions: L x W x D: 44" x 29" x 5.5"; Weight: 276 lbs
Usable Capacity:13.5 kWh; Power: 7-kW pea /5-kW continuous
Depth of Discharge: 100%; Efficiency: 90% round-trip
Operating Temperature: -4°F to 122°F; Warranty: 10 years
Needs Internet connection, broadband or WiFi or cellular, for software updates.

Tesla Powerwall 2 AC Owner's Manual

Note that the TPW can be charged by solar panels when the grid is down.
For most houses more than one Powerwall would be needed for full backup.
Up to ten TPWs can be stacked.

Note that the TPW can be charged by solar panels when the grid is down.

Modes selectable: Backup Only or Self-Powered to reserve a % for an outage.

I have ordered the Powerwall 2 for our house, which has a 7.7-kW solar PV system. I will probably set the TPW for 50% outage reserve, which might be enough to power the backup load for the rest of a day until the solar-PV system can recharge the battery the next day, if needed.

Other Battery Backup Systems

BMW House Battery

Nissan Home Battery and Vehicle-to-Home (V2H) and Vehicle-to-Grid (V2G)

"Nissan’s home battery pack, called xStorage, also serves as an electric car wall connector and it’s bi-directional – meaning that it can take energy from the car’s battery pack and feed it to the unit, power the house, or send it through the electric grid."