Stuff worth knowing about > Articles by: happyorright


Interested in technology, loves life.

Solar panels or batteries?

I have noticed in youtube videos that many people who get a home battery don’t feel it is worth the money. They say that it would have been better to buy extra solar panels, and use the grid as a battery.

First Solar panels are very cheap. Right now solar panels are less than $100 for 100 Watts. This means that you can easily buy solar panels that can provide you with the amount of power you use each day. The payback for this is quick. Even with a professional installation, most people get a payback in a few years.

When you add a home battery like a Tesla Powerwall2 or Sonnen things get more interesting. They are expensive, usually from $10-15k and while they help you save money, the pay back period is much longer. So let’s take for example a $15k Sonnen. If you pay $200 a month without solar, and buy solar and a Sonnen, how long will it take to pay back? Now the payback number can jump to 15-20 years. This means that you are betting that energy prices are going to rise in the future and/or want to be prepared for emergencies.

Let’s take the emergency preparation out of the equation. Given that utility companies are installing more renewable power and coal is decreasing, due to solar being cheaper, it seems reasonable the future will have cheaper power. Right now there are companies that give you the opportunity to buy renewable power, and I would expect that to increase in the future. The present/future will have more choices, and I think at a lower price point than currently. We have seen energy prices drop with the Pandemic, and I am not confident they will return to their former price points.

If you look at it in this way, a home battery isn’t worth it. Personally I feel a home battery is worth it, since there are always problems and there is no guarantee that prices will decrease. It seems reasonable to lock in the current prices, and if the prices get cheaper, then that is a helpful thing for society/environment.

There are more arguments that can be made about this. A breakthrough in power might be possible with cheap battery storage, or fusion power. However let’s not count on those. Let’s try to make the most reasonable decision we can with what is available to us. To me, a home battery and solar power are a winning combination.

Why do I think that LifePo4 is the best Lithium chemistry?

I want to spend my money on the best value and right now LifePo4 lithium batteries are the best in several areas: lifetime cycles, cost, and safety.

The safety is incredible. Not only does it work in a way that decreases the likelihood of exploding, it also has things to prevent fire if it should occur. It has been extensively used and tested and withstands abuse that other lithium cells would cause fire. It is the only technology that I feel comfortable using in a space that has gas like an RV or a home.

The lifetime cycles are the number of times that it can be used. Other technologies have cycles of 300, 500 or 1000. That means that if you fully charge and discharge your battery, that counts as one cycle. It is a little more complicated than that, but let’s just assume this is mostly true. So that means that for some batteries it might last a year, two years or even three years of daily cycle use. However it can last between 2000-2500 cycles and this means that it can last for 3-5 times longer than other types. It is common to see 10 year warranties on them, and some companies even have lifetime warranties. Of course all batteries can last longer if you treat them well, so your milage may vary.

The cost is interesting. LifePo4 does have a higher cost than some other lithium technologies but once you factor in the longer lifetime, it clearly is a better value. For example, let us say a lifepo4 battery will last 5 years, and another battery will last two years. The two year battery cost $75, and the lifepo4 cost $100. In another two years you will have to pay for another $75 battery, which means that your lifetime battery cost is now $150 compared to $100. You can see how this doesn’t make sense. In almost every case, buying a lifepo4 battery will save you money over buying another type of battery.

Now there are some really exotic battery technologies that have a better lifespan than Lifepo4 but they are not commercially available and cost doesn’t make sense. Right now Lifepo4 batteries have the best balance of what the average person needs. I have really enjoyed the one I have.