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> Adding battery packs significantly increase the cost of a system by an order of magnitude. At current prices. Grid-scale batteries are expensive now because

> Adding battery packs significantly increase the cost of a system by an order of magnitude. At current prices. Grid-scale batteries are expensive now because each is a unique specialty product. If we built sodium-sulfur batteries in the same volume as we build gasoline storage tanks, the price would decrease dramatically. Efficiency gains also matter, because net system efficiency is a geometric process. Consider a 20% efficient solar cell and a 20% efficient battery: the system efficiency is a ghastly 4%. And that's not counting power conversion and transmission. If the solar cell and battery were boosted to 40% efficiencies (physically possible), then the system efficiency would rise to 16%, a factor of 4 increase. That's halfway through the order of magnitude price problem you give. Then there's heating and cooling efficiency. American buildings and refrigerators tend to have horrible insulation. In many localities, merely using proper insulation closes the rest of the price gap.

maxerickson 15y ago
Does the actual efficiency of the solar panel matter? Of course it factors into the area needed to generate a given amount of power and given equal production costs more efficient is better, but people with lots of roof space are generally going to install the cheapest panels that meet their needs, not the most efficient panels they can find.
- jws 15y ago
  It matters to the extent that you need enough roof space. The last time I calculated I figured that the available south facing roof of a typical midwestern United States house was about right for the non-heating power needs of the house with current solar technology.
jws 15y ago
Lead acid batteries are 85% to 95% efficient. A good AGM is 98% efficient. As a data point, I sized the batteries at my cabin to provide two days of power under total cloud (more than enough for getting to 24 hour solar power) and the batteries cost about half what the panels did. (That discharges the batteries to 60% capacity. You also need to consider that the batteries will last about 6 years then get recycled. I mentioned AGM because they can charge much faster. If you are only interested in 24 power shifting, it might be cheaper since you'd need to buy more capacity in lead acid batteries to tolerate the charge rate. )
- deleted 15y ago
  [deleted]

maxerickson 15y ago

Does the actual efficiency of the solar panel matter? Of course it factors into the area needed to generate a given amount of power and given equal production costs more efficient is better, but people with lots of roof space are generally going to install the cheapest panels that meet their needs, not the most efficient panels they can find.

jws 15y ago
It matters to the extent that you need enough roof space. The last time I calculated I figured that the available south facing roof of a typical midwestern United States house was about right for the non-heating power needs of the house with current solar technology.

jws 15y ago

Lead acid batteries are 85% to 95% efficient. A good AGM is 98% efficient. As a data point, I sized the batteries at my cabin to provide two days of power under total cloud (more than enough for getting to 24 hour solar power) and the batteries cost about half what the panels did. (That discharges the batteries to 60% capacity. You also need to consider that the batteries will last about 6 years then get recycled. I mentioned AGM because they can charge much faster. If you are only interested in 24 power shifting, it might be cheaper since you'd need to buy more capacity in lead acid batteries to tolerate the charge rate. )

deleted 15y ago
[deleted]