I have two batteries that were 13.5kWh each. The cost was exorbitant, but I live in an area that loses power extremely often (rural), so it was worth the investment, imo. Plus, it increases the value of the house, so I'll make it back eventually.

My solar panels provide 6kW.

My whole house with the AC running uses about 4kW. Without the AC running, my house uses about 0.5kW

So doing the math right there, I could actually run 6 hours, 45 minutes with no sun and AC full blast, so I guess I was off by a little bit. But I never run the AC full blast anyway, it always turns on and off to maintain temperature, and it runs way less at night when there's no sun.

[–] Zippy@lemmy.world 1 points 1 year ago

As I said, 99 percent are grid tied no battery. You are the one percent and I think that is an important omission on your part. Your battery pack would cost around 40,000 U$ I estimate alone. Now if you are not grid tied, your solar installation will be very inefficient and often not matching your usage/charging requirements. Thus you won't be getting the most out of the 6kwh solar panels. Often getting very little return. If it is grid tied which provides access to store excess energy, that is the most efficient system. But if you include that battery pack and try to match best efficiency, then you need a much more complex charger/controller. Add 50 percent to that cost. I suspect your installation on nearing 100k if it is installed in such a way to take maximum advantage of the sun.

Now with the battery pack, you can utilize it to provide power at night allowing for maximum savings. But if you do this, there is no guarantee you will have any battery left for those frequent power outages you have. Thus to be reliable on battery, you must keep it at full charge at all times thus not getting any real financial returns on it. It is simply a 40,000 dollar 'generator' which doesn't really make any sense both from an economical or environmental sense. The good thing is that it should last a long time if it is not discharged often. But if you operate it in daily usage, you will need to replace likely every 10 to 15 years. That is pretty expensive as well.

While simple solar panel with grid tie can be both economical and environmentally friendly, battery packs make near zero sense from a return on investment or from an environmental sense. It sounds like you are using it to protect from power failures but that means it must be at 100 percent at all times ready for power failures. And if you are doing that, just install a far cheaper generator. Not only is it far cheaper, you can have days of power failure and the environmental impact is far less then the manufacturing environmental costs of batteries.