Backup Power

Grid Down

Power outages over 12 hours can have a negative impact, increasingly so the longer it goes. At 18 hours you probably want to start thinking about how to power your fridge so your food does not spoil. If you have a medical device that needs power to operate, then long power outages may have serious implications, so read on.

How Much Power?

The length of the grid down scenario you plan for, where you live and your pocketbook, will play a role in the equipment you procure and how long the system will provide emergency electrons. There are a myraid of options for short-term outages, but to figure out what you need or want, you will need to learn a bit about power consumption. You will be surprised at how much power is consumed by things like your TV, router, fridge, etc. Electron conservation is the name of the game, and every watt of energy is precious. Your lifestyle will be severely restricted as you ration your power and during a longer outage you probably do not want to flaunt your capabilities lest someone else relieve you of your equipment.

At some point your electrons will run out. If fuel is not available, then you are probably going to need to rely on solar panels and pray for blue skies (power production on cloudy days is very low). PlanB.

Power Planning

You will want to start by building a prioritized list of things you need or want to run during an outage. We will calculate total power consumed in watts using these assumptions:

Run the fridge for a week. (Gives you time to cook and consume the food).
Run 2 lamps for 4 hours every night for 2 weeks.
Run my CPAP machine for 8 hours for 2 weeks.

A few key things you need to know:

Most household appliances in the US utilize 110-120v power. Stoves, AC and Dryers use 220v power and cannot operated on the majority of small generators or solar generators which produce 110-120v power.
A "watt" is actually a watt hour - which is a measure of power consumed by the item over a 1 hour of time.
Surge Power: When an electric motor starts, there is a rush of electrons into the motor to create the magnetic field needed to spin the motor. Have you noticed the lights dim when you turn on the vacuum cleaner? This is the 'surge' required to start the motor. So when we count watts, we also need to know that the capacity of the power source must have additional power available to start the motor. That will come into play in a bit.
Most appliances use Amps indicate their consumption. To convert this: Watts = amps * voltage.

First, let's check the power consumption of each item.

1) Fridge: Most refrigerators have a sticker on the wall of the fridge that tells you the power consumption. It will typically say Volts, HZ (hertz - the frequency of the power, usually 60hz in the US) and the Amps used when the fridge runs (excluding the surge). Older fridges use less efficient motors so if you have an older model, don't be surprised if you see 5-7 amps on the sticker. These units consume a lot more power. Example:

Our fridge is rated 120 volts, 2.3 amps @ 60hz. That means it takes 264.5 watts if it runs for an hour.. Our fridge also has an ice maker and a defrost heater rated at 145 and 330 watts respectively. When all are running simultaneously the fridge can draw 264.5 + 145 + 330 = 739.5 watts. Realistically you can avoid the ice maker so let's estimate 600 watts.

The fridge compressor turns on and off based on the thermostat. So if you want to save a bit of power perhaps move your fridge temp to 36 or 38 and your freezer setting to 32.

Since the grid is down - and unless you have a 'whole house' generator with cutover and a lot of fuel available, your goal is to keep the food cool, your breathing steady and not over-use your precious watts, so you would plug in the power source for say, and hour, 2 times per day to limit the total power consumption (meaning the temps will swing more between recharges).

Calculation: Running: 600 watts * 1 hour; and 270 watts for one hour (assumes the defroster is on 1/2 the time) = 870 watts/day, x 7 days = 6090 watts, plus the "surge" watts consumed when the compressor starts.

2) 2 Lamps: A 100-watt "Rated" LED bulb consumes 11- 13-watts every hour. To calculate the usage in #2 above, we multiply: (1). 2 x 4hrs x 13 watts/bulb = 104 watts per day * 14 days = 1456 watts.

3) CPAP Machine: the CPAP has a small motor the changes speed constantly while in use, thus power consumption oscillates between 9 and 28 watts on every breath. Assuming you turn off the humidifier (water heater) to save energy, we will assume an average of 20 watts per hour. 8hrs x 20watts = 160 watts, * 14 days = 2240 watts.

Therefore our total watts needed are: 6090 + 1456 + 2240 = 9786 watts (or ~10kw). So your goal is to figure out how to supply that power for the planned period. Many of the Solar Gens store 1000-2000 watts. More watts the bigger and heavier these units become as the battery size doubles with the capacity.

Power Options

There are a couple of options that are available to meet your requirements. We are deliberately leaving 'whole house' systems out of this discussion due to their cost and general lack of energy efficiency. If hooked to propane or natural gas as a fuel source, these could make sense but you should research what happens to your nat gas provider in a longer term grid-down situation.

Single Phase: The generators (both kinds described below) produce single phase, 110-120v. power. If you have a need for 2-phase power (pool pump, well pump, etc) these do not produce dual-phase power so won't run those items. If you need 2-phase 220v, you will typically need a 4000+ watt generator.

Solar Generator

Oddly named, these are not an actual generator, but are a battery, usually lithium ion, and a power Inverter/charger that converts battery voltage to 110-120v so it can be used to power your appliances Most of these are designed to be recharged by solar panels (or grid) and can be bought in kits and can or separately.

The inverter inside the solar generator is an electronic device and it consumes power to invert the voltage to 110-120v and provide the appropriate watts. For planning assume that ~90% of the battery capacity is what you will actually be able to pull from the unit as the inverter consumes ~10%. For reference: 12% draw (88% efficient) would be inefficient; 7-8% would be very efficient. (93%)

Idle Power Consumption: The larger the inverter capacity, the more idle / working power it will consume, so you want to balance inverter power consumption v. watts produced. The inverter draws power as soon as it is turned on regardless of load, so if you don't want to leave it on if you aren't using it.

Pure Sine: you want an inverter that produces pure sine wave, not a 'modified' sine wave - this has to do with the quality of the power it delivers. Pure sine wave power protects electronics in devices. Also check to see if the Solar generator can produce power while it is being charged. Oddly some can't.

Continuous Power Rating: Indicates the max power it can deliver for an extended period. Surge capacity indicates the ability for the unit to provide extra power for sudden loads exceeding the continuous rating. The surge is there to assist with startup of applicances/motors that draw extra power at startup (pumps, vacuum, fridge, microwave).

Price: There are a lot of 'inexpensive' Solar Generator units on Amazon. They are almost all Chinese and a solid 10% failure rate or problems is the norm. The chance of getting customer support if you have a problem and/or a warranty replacement is pretty low especially if the price tag is low so be forewarned. Bluetti, Jackery and Ecoflow have been around and are pretty decent (but have a similar failure rate). So always always buy the extended warranty that includes replacement outside of the manufacturer's warranty in case they don't pick up the phone or respond.

New Unit break in: We recommend you charge the Solar Generator up and put it under load several times when you get it. This will help ensure it is working when you need it. Also note that the batteries like to be charged and last longest at 80% charge. However, having total capacity in an emergency absolutely trumps the battery lifespan, so 100% is fine. Don't leave it plugged into the wall once it is charged.

Chemistry: LIFEPO4 (Lithium Iron Phosphate) is the safest lithium battery chemistry. I would not buy one with straight Lion batteries. The batteries can discharge down to 28f safely. However, they cannot be charged until the battery is in the ~40-45f range. The charging circuit has a thermostat that prevents damage. Don't store it in a cold or overly hot location. And don't drop it in the water. If you do, RUN..!!

PLANB. The Solar Generators are designed to work with a solar panel. Typically the panels are low voltage as are the batteries, and low voltages lose power over short distances, the Solar Gen needs to be co-located with the panels.

If temps are above charging temps, you can plug in the solar panels to charge the Solar Generator. Ideally a 'greenhouse' type enclosure for both (solar heat during the day) could be a workable option. If outside then (a) make sure the generator stays dry and (b) the temps are within range. This is a partial PlanB. There are some wind turbines that turn with very slow wind speeds that might provide some power, depending on your area. Heavy overcast days produce very little solar power. {We recall an episode of Gilligan's Island where professor had Gillian pedaling a bike to charge a battery. Got Spouse? Unruly teen? }

Warmers: There are warmers for car batteries, travel trailer septic tanks. You might consider building a container for the Solar Gen and use a lead acid or AGM battery to power the heater in cold weather. There are some self-heating LIFEPO4 batteries from Battle Borne ($$).

CPAP: Small inverters and a 12v car battery will work to run a CPAP in a pinch. Lead Acid batteries hold about 1/2 their "AMPS" Rating as below this the voltage drops. Read up on this if you think this is an option.

Generators

SAFETY: Never run a gas or propane generator indoors or in a garage!

These typically run on gasoline. Some are available with 'dual fuel' - usually the larger generators (propane or nat gas). Diesel generators are used on boats and expensive motor homes are much more expensive and are not addressed here. But if you have $, diesel can be stored in large tanks and this could provide you with longer duration power options.

There are 2 primary types:

1). Inverter Generators. These use a DC generator to create the power, then have an inverter to convert the power to AC 110/120. The generator responds to load, and will increase the engine RPM to produce more power if the power load goes up. Most have an ECO mode. The generator runs at a slow speed producing about 1/4 the rated power - so if you aren't using the power, it can save quite a lot of fuel, which is a huge benefit in a grid down situation where you are trying to conserve resources.

Another benefit is they tend to run quiet compared to larger generators.

2). Regular Generators. These typically run at a constant RPM enough to produce the power rating of the generator. Little point producing 3000 watts if you are using 400. They have fallen out of favor but are considerably cheaper, but may not produce clean power. And they are much noisier and may attract unwanted attention and they consume a lot more fuel. They make sense if you have beefy equipment you need to run, such as 220v items (well pumps, dryer, stove) so it depends on your requirement. When reviewing specs, each unit will tell you how much fuel it consumes, it will also tell you at what load level, so make sure you understand that 5 gallons of gas for 6 hours and 1/2 load means 3 hours at full load.

We utilize a combination of the Solar Generator and Inverter Generator. We run the Generator at night when its dark and charge the Solar Generator and run the fridge/etc. Then once charged, the Solar Generator is used for lights and other stuff during the next day. This significantly conserves fuel and means you don't have to run the generator over-night for the CPAP (in our example).

We are biased toward Honda equipment as we have found them to be extraordinarily reliable over many years. Based on our usage, the EU2200 is sized to run 1800 watts continuously with moderate surge capacity to 2200 watts. See picture at the top. $1150. 2 EU 2200s can be cabled together to produce 3600watts so if you need more power that might be an option. These are in the 55lb range

Gasoline Storage

Using a regular generator for more than a day or 2 requires you to store a fair amount of gasoline. The EU2200 running at ECO speed will run about 8 hours on 1.1g. Used in combo with a Solar Generator you can leverage the 5 gallons to 6 or 7 days as long as you aren't running heavy loads. See the Fast Start Shopping List for more info on fuel additives, etc.

A decent funnel, wide mouth suggested to ease filling the tank.

Charging Cell Phones - Short Term (1-2 days)

Cell Phones / Recharging Phones or Walkie talkies

Small solar powered battery backup systems can be used to charge a phone or two and with decent sunlight the pack can be recharged and add time to the operation of your phone. If the grid is down you are unlikely to have cell coverage, so you might want to turn your phone off to conserve power.

Look for a device that can be wall-charged (ready to go in an emergency) and has a high mAh (mili-amp) storage as possible. These generally start at 10k mAh and go as high as 65k mAh in small units. These devices tend to have a high failure rate (this is typical) so consider buying an extended warranty so if it fails you can quickly replace it. In general: the larger the solar panel, faster charging. 3"x6" panels produce very little power so keep that in mind.