What stops people from getting into solar is a complete confusion over the components you need and how much electricity you get out of those components. Deceptive online solar stores throw big numbers around, like 5,000 watts, similar to what you’d get from a small gas generator, but even lower numbers like 1500 watts can be deceptive. Watts, amps, volts! It can all be very confusing. When you try to figure out how much electricity the kit makes, the numbers can bog you down.
The electrical measure of the “watt” is the most convenient capacity measurement of electricity because it is always the same regardless of the voltage, and this is important because solar panels produce 12-18 volts. Household current is 115-120 volts, and it is a different kind of current than what is produced by the panels. Solar panels produce direct current, or DC, and your microwave, refrigerator and lights run on alternating current, or AC. The other term you’ll hear is “amps,” but amps change as voltage changes, as I’ll explain. Anything given to you in amps can easily be converted to watts.
Wait, don’t let your eyes glaze over at the boring details! You get watts very simply by multiplying voltage x current, measured in amps. So 12v x 1 amp is 12 watts. 120v x 1 amp is 120 watts. As you can see, when it comes to power consumption or generation, amps can be apples and oranges, depending on the voltage. Buying solar can be confusing because both amps and watts are used for many of the components, so you find yourself having to do the math in your head to try to figure out what you are actually buying.
- The solar panels. – We all know what these are, but they come in tons of different shapes and sizes. A solar panel is usually rated in watts, and they produce usually between 12-18 volts. So if a panel is 12 volts, and you see it advertised as a 50 watt panel, that means that at peak production and optimal output it produces roughly four amps… at 12 volts. If you look at the back of your 50-inch flatscreen TV, it will probably say that it uses 250 watts, but remember, that is at 120 volts. So it uses roughly two amps. See, this can be confusing. If they were the same voltage, the panel could power the TV set’ but in real life it only provides about 1/5th of the power required. In practice, panels don’t run at full rating almost ever, so more likely, in order to power the TV for one hour, the solar would have to work at partial power for a full day. That is why all solar system have a storage battery, or batteries. The battery allows you to collect up electricity from the sun, then use it for higher drain devices.
There are, for the record, two types of solar panels, single crystalline silicon, polycrystalline, and amorphous. Generally the single is thought to be better, then the poly, then the amorphous. The single produces the most power for their size. Then the poly, and the amorphous are the largest for how much power they provide. But amorphous panels tend to give you more power under non-direct sunlight.
The poly Harbor Freight panels are rated at 15 watts each. There is a note in the directions that for the first four months of service, polycrystalline panels often lose 20% of their input power. Combined, the system is rated at 45 watts. I doubt that in full sunshine it hits 30 watts, so if you want to watch the big flatscreen, it’ll probably take you several days of full sun to store enough power for one hour. Small TVs use less power of course, but you get the point. Panels can be wired in parallel for more juice, and that is what most kits will do for you. This kit comes with a three-way splitter with internal parallel wiring for the three 15w panels.
- The batteries. – All batteries are not created equal. I’m sure you have heard of deep cycle, or marine batteries. These are meant for long-term storage of electricity, where you might not come back to use the battery for a while. They will lose their charge slower than your average car battery, but they are still not the ideal battery for solar applications. The solar stores sell batteries that are rated in amp/hours. Harbor Freight sells a 35 amp/hour battery for $69.99, but I chose to buy 100 amp/hour batteries from a proper solar company for about $250 each. They are rated to last 10 years, and I am in no way endorsing them, because I have only tried them for function as of yet. We also bought some Lithium Iron Phosphate(LiFePO4) batteries to try as well, but they are $600 each for the same 100 amp/hours. This is still a relatively new technology and the 12.8v battery is really 4 cells strapped together. We will be back with a full review of both of these batteries in the future.
- The charge controller. – This is a piece of gear that many people overlook, and it is one of the reasons why starting with the Harbor Freight System is so useful. The charge controller that comes with this small system controls both the inflow and outflow of current. If the battery is fully charged, the charge controller cuts the electricity off coming from the panels so as not to damage the battery. If you are using the electricity from the battery and the voltage drops too low, the charge controller cuts off the current going out, so as not to permanently damage the battery by draining it too low.
Charge controllers are rated in amps, which you would assume means that they can handle their rating both in and out. The Harbor Freight charge controller that comes with this system is rated at four amps (at 12 volts=48 watts). My refrigerator runs at 10 amps (at 115 volts=1100 watts), so even if I had a lot of batteries and panels to support that much electricity, this charge controller wouldn’t work. For charging phones and tablets, and running 12v fluorescent and LED lights, it is fine though. The kit actually comes with a multicharger, ports for 3v, 6v, 9v and USB, plus two sockets for included 12v lights. Harbor Freight sells a 30amp controller, but at 12 volts (360 watts), that will not even power the fridge. I put the 250-watt TV on this controller just to see what would happen, and it did clip the power so that the TV couldn’t run. The same inverter, directly connected to the battery, powered the TV for several hours.
- The power inverter. – When you see an advertisement for “3000 Watts” or any high number in a solar power system, usually they are referring to how large a power converter comes with the system. As you can see from the pictures, I paired the Harbor Freight system with a 400 watt converter that I bought at BJ’s, but it is way overkill for this solar setup. At 12 volts, it would need the 30 amp controller at least. The power inverter merely takes DC power and turns it into AC, while upping the voltage from 12 volts to 120 volts. You have probably used a similar inverter in your car to power a laptop, and many cars have them built in these days. The difference between that inverter and an inverter meant for solar is the capacity. I was not able to power a really butch Dell laptop from my car’s inverter, and its power pack only ran 1.3 amps, which is under 150 watts. Inverters get expensive in the high numbers. There are some very expensive electronics and cooling elements when you get up into high-power handling.
Also note that you don’t absolutely need an inverter if you plan in advance to use 12-volt lights and appliances. This is a good idea, because an inverter is just a transformer, and transformers as a rule eventually fail. If there is one point of possible failure in a solar system, it is in the inverter. And having a backup isn’t always the answer. You could blow your inverter without realizing that you have a short in an appliance, then burn another one right after it. The answer is 12-volt lights and appliances, and we hope to cover that in a future article.
Ebay has become a clearinghouse for solar. You can buy kits or individual components, and there are very good buys on brand name bulk components. For instance, you can buy 16 100amp/hour batteries for $3199, shipped nationwide. Just remember that your charge controller has to be able to handle your outflow, the same as your inverter. Make sure you look at the numbers on all the stuff you are getting. Just because something is sold as a package doesn’t mean the components go together.
This Harbor Freight system is not totally pathetic. For the money, it isn’t a very expensive way to keep your home lit indefinitely once the power goes out for the foreseeable future. Most small laptops run in the 60 watt range, so this system would probably keep up with them. You can’t get into a solar system for much cheaper than this, plus the cost of the battery. This system is underpowered for most household devices and isn’t worth an inverter. But if you managed to charge up your battery over the course of a week or so, you could always skip the charge controller and put the inverter directly on the battery. Just do the math so you don’t use much more than half the amp/hours.
What can you power with solar? That depends on how many square feet you have to put your panels, and how much money you want to spend. You won’t be able to heat your house in the north, or cool your house in the south with solar, unless you plan to spend tens of thousands and make your house stand out like a signal mirror to passing aircraft (no thanks). You also probably can’t count on solar to cook your food, or run your washing machine. There are 12-volt small refrigerator freezers though, and don’t discount the value of lights. If you had to decide between $250 worth of flashlight batteries or this system and the $70 35 amp/hour battery, I would choose the latter. In our next installment of solar, we’ll be testing a much more robust system in the 1800 watt range. Summer is here and hopefully it will mean a lot of sunshine, if Yellowstone doesn’t erupt of course. Gulp.