You need to compare apples to apples.
The Lithium Ion systems have a higher percent of useable capacity. If you want your deep cycle lead-acid cells to last more than a few months, you can't cycle them fully. The Lithium ion cells are rated at there warrantied daily discharge (not their full capacity), you can't use all of the lead acid rated capacity. Also, prices are in AU$ and include GST! Also, you pick a cheap lead acid solution to compare with the "average" lithium Ion solution. But many of those prices are old and out-dated. Also, you can't just compare cost per KWh, you need to account for how long they last and how much the storage capacity decreases over time. Total system cost.
Lithium Ion beats lead acid in so many ways it's not even close.
Read my numbers again.
I *DID* compare on a usable capacity for usable capacity basis. My calculations for the lead acid where based on a 50% DoD per cycle utilization, and based on expected life at 50% DoD from the datasheet.
Surette S-1660 $399
2 volts
1284Ah
2v * 1284Ah = 2568 Wh = 2.568 KWh * 50% = 1.284KWh usable
$399/1.284 = $310 / installed usable KWh
From the lifespan table 50% DoD = 1,280 cycles
1.284 KWh/cycle * 1,280 cycle = 1,643 lifetime KWh
$399 / 1,643 lifetime KWh= $0.243 per lifetime KWh
The numbers in the article are based on their published usable capacities... which I would assume is no more than 60-70% of the total installed capacity or else there is no way they are achieving lifespans in the multi-thousands of cycles. Lithium degrades when stored both at full and empty so the usual solution is to cutoff the charge at 80-90% full( around 4.0~4.1vpc no load) and then cutoff discharge at 20% full (around 3.7vpc no load)
The lead solution I picked was not cheap at all. Rolls-Surette is the Cadillac of lead acid off grid systems, they are big supplies to the railroads, marine power, etc. If you want cheap you get china built cells from Universal Battery Group, or surplus forklift, telco, submarine batteries.
I also roughly adjusted the numbers in the link for the 79c to $1AUD current exchange rate as I stated.
LIthium does have advantages (easier to measure charge, lighter/small for the capacity, higher charge rates, more efficient charging), but its still cant beat lead on a cost/capacity basis in stationary power setups. It probably will eventually, but not yet. Lead is just plain
cheap.
Of course, with Lead you have to design your own setup, buy all the components and wiring individually, install, test and maintain. And your basement looks like the battery room of a U-boat. With something like a Tesla powerwall you get a turn-key, futuristic looking solution and instant green cred with all your McMansion buddies.