Replies

1. GBA Editor
   Martin Holladay | May 17, 2018 06:25am | #1

   Ethan,
   Q. "What - if anything - can be run off off a battery? induction stove? ERV? Minisplit? Well pump?"

   A. All of the above are technically possible. The limitations aren't technical; they are financial.

   Off-grid homeowners routinely operate a small (1/3 hp or 1/2 hp) well pump, but it's usually the largest load in the house. An ERV is possible, but it runs too many hours per day for most off-grid homeowners to consider using one. (It runs down the battery in winter.) You have to be unusually wealthy to be able to afford to buy a battery large enough to provide meaningful operation of an induction stove or minisplit -- in other words, you'd need a battery and inverter system that cost more than $30,000.

   Q. "How can a solar-power house be allowed to operate while the power is out - a grid cutoff?"

   A. If the sun is shining, there are inverters that allow a very limited use of power when the grid is down.
   For more information, see Getting Power From Solar Equipment When the Grid is Down.

   Q. "What are other ways for a designer/homeowner to prepare for when they are unintentionally off-grid?"

   A. Neophytes to off-grid living often think this is complicated, but it isn't. When the power goes out, a grid-tied house needs a generator fueled by gasoline or propane. It's as simple as that. The generator will cost 1/5 or 1/10 as much as a battery/inverter system capable of handling the same load.

   For more information, see Planning for Backup Power in an All-Electric House.

2. 
   kjginma | May 18, 2018 10:19pm | #2

   Ethan, consider having a manual generator transfer switch added to the main panel so that you could power the whole panel (shutting off non-essential items that are beyond what your generator can support).

   You should definitely consider the virtues of a 12v DC lighting system in the house. Not only good for emergency but in the bedroom, it allows you to routinely disconnect from 'dirty electricity' if you are at all EMF-sensitive. We are considering this now in our new house design. Obviously very friendly for battery source.

   Many small devices run from USB power, so that is easiest to handle in off grid.

   There are many websites that make suggestion how to 'hack' power inputs to the large variety of consumer goods (monitors, laptops, ereaders) to eliminate the proprietary transformers from the AC to directly drive them from DC, but I value the UL safety label more than occasional grid-off use.

   You might want to consider various defensive strategies such as keeping freezer full of ice to lengthen the ride through of power outage.

   If water pressure cannot be maintained on your well, then a bucket toilet with a bag of sawdust will do admirably.

   Solar oven (either adhoc with aluminum foil or a purchased product) can replace induction though simpler is propane camping stove outside. Relying on electricity that comes from a generator is great as long as you have a supply of fuel. I am old enough to remember the arab oil embargo in 1970s where gas lines were long and you could only get some on alternate days, Not all off-grid situations are weather-related.

   Although GBA likes to announce Solar Hot Water's demise (on financial merits of PV instead), in a grid-down situation it does not take much energy to move those fluids through the panels and into the exchanger. Just sayin' ...