This is probably the first and most common question people have when they encounter the term “solar generator”. It’s perfectly understandable, since the name “solar generator” isn’t actually very accurate. The reason these devices are called solar generators is because of the product that they are meant to replace – that is to say, fuel-powered generators. You know, those machines that make a lot of noise but put out AC power so you can still use your appliances when the power is out.
A solar generator is meant to be a drop-in replacement for gasoline-powered portable generators, except you fill them up with nice green solar power. Ironically, solar generators usually have no solar capture capacity at all. You have to buy solar panels separately. They don’t need to be filled up with solar power either. You can just top them up with grid electricity and keep them as a backup. Yet, these devices are at their best when you actually use them in the field, with solar panels to keep them filled.
So, in short, a solar generator isn’t actually a generator. It’s a power storage solution meant to act as a drop-in replacement for gasoline generators. You need to add solar panels as an additional cost.
The Parts of a Solar Generator
A solar generator can come in a variety of forms, but there are always several key components common to them all.
The first and most obvious component is the battery or cluster of batteries. Lithium ion technology is a popular choice, but any solar battery technology is a possibility. You might find solar generators which use AGM or gel lead acid batteries, for example. You can read more about the types of solar battery technologies in this article on solar storage.
Along with the battery, the generator will also include a charge controller. This is a device that charges the batteries in a way that keeps them healthy. It won’t let them get too low or overcharged. This is the bit that the solar panels connect to.
The final part of the puzzle is an inverter. You can read all about inverters in my inverter explainer article. Here I’ll say that an inverter’s job is to convert the direct current power stored in the battery and output alternating current so that you can use it with the same appliances you already have in your house.
One thing worth noting about modern solar generators is that they will often have USB ports built in for charging. These don’t go through the inverter and pipe out DC power straight from the battery after voltage regulation. That’s because it would be very wasteful to convert DC to AC, only to then use an AC to DC charger again. So unless you have a very good reason for it, don’t use the power adapter that came with your phone or tablet. Just plug it directly into the USB port.
DIY Solar Generators
Looking at the list of components and how these generators work, you might have noticed that this is essentially a miniature version of solar power systems that run entire homes. This means you can make your own generator if you want to. While this might not actually save you any money, it does mean you will have control over the various components. Off-the-shelf generators are sleek and compact, but you have to take what you get. I’ve seen people convert trolleys and other makeshift enclosures to create portable (or at least movable) solar setups. That’s a discussion for another day, but it’s worth knowing that there’s no black magic involved in creating one of these devices.
What Matters in a Solar Generator?
Although all solar generators have the same basic list of components, they vary quite a lot on an individual basis. You should make sure that the various components and specifications add up to something that you can actually use. Otherwise you would be buying a very expensive paperweight. Let’s look at the specs that matter.
Battery Capacity and Replaceability
You probably don’t have to be told this, but the solar storage capacity of the generator is the first thing you should look at. When there is too little solar power or it’s dark, you’ll have to rely on the power reserves of the generator.
Just like a huge power bank, the capacity is measured in ampere hours. What you really want to know is how many watt hours the unit provides. If it’s not stated explicitly, you can work it out by multiplying the amp-hours with the voltage of the battery. That gives you a theoretical maximum watt-hour figure. Then you take the watt-hour consumption of the appliances you want to run on that battery and work out roughly how long you can run them before the storage is empty.
That’s only the theoretical number. Take about two thirds of the theoretical watt-hour figure as the realistic amount. Then make sure you either buy a large-enough solar generator to cover your needs, use power-efficient appliances, or go without some of your appliances some of the time. The good news is that many manufacturers now also give some more human-readable capacity specs. For example, how long a typical fridge will run or how many full charges you’ll get on a typical laptop.
Finally, see if you can buy a new battery when the original dies. How hard is it to do? How much will it cost? All batteries die, but it would be a pity to buy a whole new generator if only the battery has bitten the dust.
Inverters have come a long way and most are now more than 95% efficient. However, in other aspects you need to pay attention to some important functions your generator’s inverter may or may not have.
For example, does the inverter allow you to convert AC to DC power, so that you can fill up the solar generator before loading it in your car and taking it on a camping trip? Can you charge it from a DC source such as a car lighter socket? Depending on your needs, this sort of flexibility could be very important!
Most important is the total amount of wattage that the inverter can provide at once. Let’s say it can provide 1KW of total power. That means all the appliances you have running from it should not exceed that total.
You should also avoid solar generators that have a big mismatch between how much battery capacity there is and how much the actual battery can hold. That’s like having a Ferrari with five liter fuel tank. Sure it will go fast, but only for a few minutes and then you’re stranded!
Solar Input Capacity
Solar panels generate a certain amount of maximum wattage under stable test conditions. If you put them in a good spot, they should actually average close to the claimed peak performance. The problem is that there is no point in hooking up panels to a solar generator that can’t handle the total amount of juice coming into the system. Make a note of what the recommended solar wattage is that the generator can take.
Even with solar generators that include solar panels, they may not be the maximum possible. So you may be able to add more panels later. The bottom line is that you should match the output capacity of the solar panels to the input capacity if you want good recharge times and decent live usage of solar power.
The whole point of a solar generator is to stuff an entire solar power system into a form that actually makes it possible to move it from one place to another. We all have different portability needs and they have to be balanced against other aspects of the generator.
Batteries, especially lead acid batteries, are heavy – which means large-capacity generators should have good quality wheels and strong, comfortable handles, as well as a shape without sharp edges that could hurt someone.
Also, consider how you will be using your generator. Will it be stationary in your garage, to be used in case of emergency? Will you drive it around in a car? Will you have to push or carry it for long distances? The details of your portability needs will determine how portable you need the system to be. Make sure that the generator in question has the right wheels for where you need to move it around. If you need to cart it around on dirt, pneumatic wheels with a bit of grip are a good choice. If it’s just paved terrain, then good quality caster wheels will suffice.
Regardless of the above, pay attention to the total weight of the system. Given the total capacity needed, decide if it’s more practical to buy multiple systems rather than just one big one.
Can it Be Chained?
Speaking of capacity and weight, some solar generators can be chained to external batteries in order to boost their capacity. This is a very useful feature since it means you can expand the system over time. It’s cheaper than having to buy multiple generators, each with their own inverters and charge controllers. By chaining several batteries together you can let the system grow with you. That being said, this is not the sort of thing that’s practical on a camping trip. But then you don’t have to take chained batteries with you on those trips either.
Quality and Durability
Unbranded components are usually a sign that corners have been cut. Who made the inverter, battery, and charge controller? What’s their reputation? Do those components have their own reviews? Given how large a purchase one of these generators can be, it’s worth doing this level of homework.
Of course, you should also have a reasonable warranty period. Two years is fair – if any component is going to fail due to quality issues, it will probably be in that window.
The outer casing is also something to look at seriously. A plastic casing and plastic wheels are usually a bad sign. You don’t want to buy a generator that won’t stand up to a bit of mild abuse as you move it about. Yes, metal will make it heavier, but will also be more protective of the inner components.
That’s it! The most important things you need to know before buying a solar generator!