This guide shows how solar generators work and what features you’ll find on most units. Solar generators differ in terms of power output, so you’ll learn how to pick the right-sized generator to fit your needs as well as typical prices for various sizes and features.

How to Choose the Right Size Generator
Item Wattage Expected Hours
of Use per Day
Air conditioner (room)
Coffeemaker
CPAP
Freezer
Hair dryer
Laptop computer
Light bulb (incandescent)
Light bulb (LED)
Oxygen concentrator
Portable Heater
Refrigerator
Toaster oven
TV (30-inch LCD)
Window fan
Minimum Watt-Hour Capacity You Need 0
Minimum Amp-Hour Capacity You Need 0
Your Results:

Knowing how many amp-hours of capacity you need will help you decide the size of generator you need to buy. Generally, the more you will demand of your generator, the larger the generator needs to be.

Classes of Solar Generators

The solar industry has evolved. Consumers today have a wide range of options, from mini-models that charge mobile phones to large, heavy-duty units for construction sites and military bases.

Backpack Solar Generator Small-Appliance Solar Generator Mid-Range Solar Generator Extended Home & Commercial Solar Generator
Description & appropriate use Small solar panel and integrated battery. Typically includes a stand or mounting mechanism allowing user to position the device for maximum sunlight. Premium models recognize the type of connected device and feature LED readouts of sun-exposure levels. Some have rugged exterior construction suitable for outdoor use. Designed to recharge phones or USB devices and power a mix of appliances, such as lights, TV, laptop or tablet, microwave, portable heater, fan and low-current medical devices, such as CPAP machines. Designed to recharge USB devices, 12-volt and AC ports. Powers small and medium-sized household appliance for a longer period than smaller generators. Has inputs for attaching additional solar panels or batteries. Can power high-current medical devices, such as oxygen generators. Can handle high-current devices, such as electrical tools, or can power several small appliances for an extended period of time. Features inputs for attaching additional solar panels or batteries.
Typical outputs USB only USB, 12-volt and 120-volt AC USB, 12-volt and 120-volt AC USB, 12-volt and 120-volt AC
Weight 1 lb. or less 20 to 80 lbs. >100 lbs. >100 lbs.
Sustained load 7–20 watts 150–500 watts <1,200 watts >1,500 watts
Amp-Hour rating 4 AH or more 30 AH 80 AH 100–200 AH
Cost Less than $200 $350 to $600 $1,200 to $2,000 $2,000 to $5,000

How It Works: Solar Generator Secrets

A solar generator is a simple system consisting of five key components. Look for these five things when buying or building a solar generator:

1 Sun

Local weather patterns make a difference, but almost everyone has access to sunlight via a roof, porch, terrace, yard or nearby clearing. The best location for your solar generator is the one that receives the most direct sunlight each day.

2 Solar Panel

This is a panel filled with individual photovoltaic cells, which have the ability to convert photons of sunlight into electricity. Solar cells are made of silicon crystals cut into super-thin wafers or a film made of silicon, cadmium telluride or other materials. The cells are connected in a series to develop an electrical current that charges a battery.

3 Battery

The battery stores power so you can draw upon it later, even when the sun’s not out. The most common batteries are the lead-acid type. For a solar generator, you’ll want a high-capacity, deep-cycle type rated for 12 volts.

4 Inverter/charger

Battery power is direct current (DC), and your appliances need alternating current (AC). So you need a device to convert DC to AC, called an inverter. Look for an inverter with one or more AC plug inputs to accommodate your appliances. A 2,000-watt voltage inverter provides sufficient power to run most home appliances or power tools.

5 Power Outlets

Your battery’s DC output will charge laptops, phones and other devices that have internal inverters. For appliances, you need a safe and reliable way to bring the electricity back to your home, which can vary from a heavy-duty extension cord to a more permanent wiring solution.

Your generator should come equipped with a voltmeter or some other indicator to let you know the panels are producing power. Solar panels generate between six and 24 volts of direct current (DC) power. As the infographic shows, the charge controller handles topping off your generator’s battery.

You’ll find that efficiency levels among solar panels differ. Efficiency refers to how well each cell converts the sun’s photons into electrical current. So a panel with a 15 percent efficiency rating produces 50 percent more electricity than one with a 10 percent rating. (Don’t be alarmed by the seemingly low efficiency numbers: the world record for solar panel efficiency is just over 40 percent). The other main difference among panel brands is how long they take to recharge.

Depending on your solar generator goals — the number of appliances and how much power they draw — you may want more than one solar module and battery, so you can string the modules together and produce more electricity. A solar panel typically costs a few hundred dollars and is available from a provider in your area. With proper installation and maintenance, your solar panel will last, on average, for 20 years.

Common Solar Generator Features

Most solar generator units have digital displays that show energy usages, recharge rates and stored energy levels. You’ll find a range of options when it comes to power outlets and inputs, controls and packaging.

Power Outlets

Many solar generator configurations supply three types of outlets:

5-volt USB

USB ports for mobile phones and tablets

120-volt AC

Familiar outlet in homes and offices throughout North America

12-volt DC

Common outlet found in autos and trucks for the last 60 years

The number outlets featured on a solar generator is somewhat related to the amount of power the unit can generate. It’s generally not a good idea to increase the number of outlets by adding a power strip unless you first determine that the generator can provide the power necessary for additional appliances.

For heavy-duty use, a solar generator may include an external 30- or 50-amp outlet for charging external batteries or powering an RV.

Power Inputs

Some units have inputs that enable you to charge your generator by connecting it to a nearby wall outlet, which can be useful when your stored energy is running low and the weather is overcast.

You might also look for a unit with one or more heavy-duty inputs that allow you to add solar panels.

Generator Controls

As solar generators become more sophisticated, they may include displays and controls beyond energy usage and amount of stored energy, including:

  • Gauges indicating average usage per day and month

  • Indicators showing how much CO2 you’ve avoided by using solar energy

  • WiFi-based controls for remote monitoring and online management

Packaging

Look for convenience features, such as beefy handles and rain resistance. Big, heavy generators should have built-in wheels.

Solar Generators & CPAP: Medical Devices On the Go

Traveling with a medical device isn’t hard. Most medical devices, and all of those sold as portable devices, will work with the 12-volt power outlet in your car. You may be considering a solar-powered battery pack for your continuous positive airway pressure (CPAP) device, oxygen concentrator, infusion pump or nebulizer, which will allow you to go camping or otherwise live off the grid and still keep your medical device powered.

Follow this guide to determine which size commercial solar-powered battery pack you need and how to make your own compact solar-powered battery pack that costs much less than a commercial pack.

Does Your Medical Device Use a 12-Volt Adapter?

Photo credit: Resipironics

Most medical devices labeled as “portable” can plug into a 12-volt DC outlet in a car as well as a wall outlet, which provides 120 volts AC. If your CPAP machine or oxygen generator has an option for plugging into a 12-volt automobile outlet, then you’re halfway there.

For example, Respironics offers 12-volt adapters for some of its CPAP devices. (See image to the right.) An adapter like this replaces the cord you use to plug your device into a wall outlet.

This does not necessarily mean you can use a Respironics 12-volt adapter for any CPAP machine. Buy one designed to work with your device. Contact the dealer or manufacturer to learn whether you can buy a 12-volt adapter that will work.

What To Do If Your Device Doesn’t Have a 12-Volt Adapter

Even if the manufacturer of your device doesn’t offer a 12-volt adapter that’s compatible, you aren’t out of luck. You will need to learn the meanings of two technical terms: “inverter” and “sine wave.”

Jargon Word No. 1: Inverter

An inverter converts 12 volts DC power — like what comes out of a car battery — into 120 volts AC power, which is the amount that comes out of a U.S. wall outlet.

Inverters are nifty devices, but they are not perfect. Most are inefficient and waste about 20 percent of the power they receive from batteries. In simple terms, if your battery is rated to power your device for 10 hours, your inverter essentially throws away about two hours’ worth of power, leaving you with about eight hours of power to use. Inverter inefficiency is why you should use the manufacturer’s 12-volt adapter when operating on battery power.

Jargon Word No. 2: Sine wave

This is not a physics lesson, so we’ll skip ahead to our recommendations. Inexpensive inverters often output energy in what’s called a “modified sine wave,” which often isn’t compatible with major appliances. You do not want a modified-sine-wave inverter. Instead, look for an inverter that offers a “pure-sine-wave.” It likely will cost more than the modified type, but it’s what most electrical devices are designed to run on. If your device won’t run on 12-volt power, then be sure to buy a pure-sine-wave inverter.

How Large Does Your Battery Pack Need to Be?

Battery capacity is like a gas tank on a car. Generally, a car with a bigger tank will allow you to drive farther than a car with a smaller tank. However, we know it’s not quite that simple. Some cars get better mileage than others. In order to know how far you can drive on a tank of gas, you need to know both your car’s average miles per gallon and the size of its tank.

When it comes to batteries, here’s a fair rule of thumb: The heavier the battery, the greater its capacity. Of course, there are exceptions to this rule — batteries are packing more power per pound as technology advances. U.S. gas tanks are measured in gallons while battery capacities are measured in amp-hours (AH). Like the gasoline capacity of auto fuel tanks, the more amp-hours in a battery, the better.

You’ll need to know how many amp-hours of battery capacity are required to run your device for a set number of hours. An 8 AH battery will power a device consuming one 1 amp of current for eight hours. Or, the same 8 AH battery will power a 2-amp device for four hours or a half-amp device for 16 hours.

The following table shows how much power these medical devices need to operate for eight hours:

Device Energy used per 8 hours at 14.4 volts Size of battery for 2 days of use at 8 hours/day
Transcend miniCPAP 8 32 amp-hours
HDM Z1 8 32 amp-hours
iGo Portable Oxygen Concentrator 12 to 50 amp-hours 50 to 200 amp-hours
AirSep FreeStyle Portable Oxygen Concentrator 10 to 48 amp-hours 40 to 200 amp-hours

Power consumption varies with flow rate, efficiency of device, and its settings. Humidifier use increases power consumption dramatically.

Here is a list of five commercial battery packs you can buy that will power CPAP and other medical devices.

Device Capacity Features Cost
Goal Zero Yeti 150 Solar Generator 14 amp-hours Handy, small package with USB, 12-volt DC, 120-volt AC outlets $230
Universal Super CPAP Battery Pack 8.3 amp-hours Adapters for various medical devices $249
Zamp Solar 600W 12VDC Pure Sine Wave Inverter and CPAP Power System Does not contain a battery. More of a DIY kit requiring assembly than a ready-to-go system $656
Respironics Battery Pack (No DC Cable) 14.4 amp-hour Designed for Respironics medical devices that operate on DC power. $299
Solar Charger for Transcend Batteries N/A Folding solar panel designed to work with Transcend medical device mobile battery systems. $225

You have the option to build your own solar-powered generator, and you can find instructions for doing so on several websites. However, if you’re not handy or experienced with wiring electrical parts, you’re better off buying a preassembled solar charger. If you prefer to do it yourself, consider the Zamp kit in the table above.

Resources

Choosing a solar generator requires doing your homework. Fortunately, many online resources are available to help you through the process.

  • My Gen Set Find information about how to choose a solar generator, along with a handy chart of ratings, wattages and prices for a select number of brands.

  • Choosing a Portable Renewable Energy Generator A good guide provided by AltEnergyMag.com for those who are looking to match personal usage to the right generator.

  • Choosing a Backup Generator From Mother Earth News, this article offers a detailed examination of backup generators, including solar, with lots of useful information (though some of it may be dated).

  • Portable Solar Home Generator Buying Guide This well-written, comprehensive article from eBay covers all the important points of the solar generator buying process.

  • Portable Solar Generators 101 An examination of factors to consider when choosing a solar generator, such as “sustainable maximum output load.”

This page was created for informational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis or treatment. Seek the advice of your physician or other qualified health provider with questions you may have regarding your medical equipment. Never disregard professional medical advice or delay in seeking it because of something you read here.