{"id":284890,"date":"2026-08-04T15:49:04","date_gmt":"2026-08-04T13:49:04","guid":{"rendered":"https:\/\/www.heiwit.com\/?p=284890"},"modified":"2026-08-04T16:33:06","modified_gmt":"2026-08-04T14:33:06","slug":"compare-storage-battery-prices","status":"publish","type":"post","link":"https:\/\/www.heiwit.com\/en\/confrontare-prezzi-batteria-accumulo\/","title":{"rendered":"How storage battery prices really compare"},"content":{"rendered":"

Two batteries with the same list price can end up costing twice as much as each other by the end of their lives.<\/strong> It is not a paradox: it is what happens when you compare the purchase price instead of the cost of the energy that that battery will actually be able to store and deliver over time.<\/p>\n\n

It is the comparison that installers find themselves making every time they present a quote, often in front of a client who only looks at the bottom line. Here we try to list the four numbers that really matter, and at the bottom you will find a calculator to do it for your own.<\/p>\n\n

The list price does not state how much energy costs<\/h2>\n\n

You don't buy a battery to own it: you buy it for the amount of energy that will pass through it before it stops being useful. The correct metric, therefore, is not the euro per kilowatt-hour nominal<\/em>, but the euro per kilowatt-hour actually cycled<\/em> over the system\u2019s lifetime.<\/p>\n\n

To work this out, you need four pieces of data, which any reputable technical specification sheet will provide.<\/p>\n\n

1. The rated capacity<\/h3>\n

The stated kilowatt-hours. It\u2019s the figure everyone looks at, and it\u2019s also the least informative of the four, because on its own it doesn\u2019t tell you how many of those kilowatt-hours are actually usable.<\/p>\n\n

2. Depth of Discharge (DoD)<\/h3>\n

The percentage of capacity that can actually be used without damaging the cells. A 10 kWh battery with a DoD of 80% provides 8 kWh per cycle, not 10. This is the difference between the rated capacity and the available capacity, and when comparing two products, the 20% may represent the actual value.<\/p>\n\n

3. The number of cycles<\/h3>\n

How many full charge and discharge cycles can the battery withstand before reaching the end of its useful life? Please note: A number of cycles without the residual capacity to which it refers is meaningless<\/strong>. Saying \u201c6,000 cycles\u201d is like saying \u201cit lasts a long time\u201d: the right question is 6,000 cycles \u2013 up to what percentage of remaining capacity?<\/em><\/p>\n\n

4. Residual capacity at the end of its service life<\/h3>\n

The percentage remaining once the stated number of cycles has been used up. This serves two purposes: to make the number of cycles comparable, and to estimate the average energy actually available over the system\u2019s entire lifetime, which lies halfway between the initial and final capacities.<\/p>\n\n

The formula<\/h2>\n\n

Taken together, these four figures give the total energy that the battery will cycle over its lifetime:<\/p>\n\n

Total energy = capacity \u00d7 DoD \u00d7 cycles \u00d7 average degradation<\/strong>
\nwhere the average degradation is the average of 100% and the declared residual capacity.<\/p><\/blockquote>\n\n

And that brings us to the key figure:<\/p>\n\n

Cost per cycled kWh = price \u00f7 total energy<\/strong><\/p><\/blockquote>\n\n

It\u2019s a calculation that takes just thirty seconds and turns quite a few comparisons on their head. Here\u2019s the calculator: enter the details of the battery you\u2019re considering on the left, and compare them with those of ours on the right.<\/p>\n\n

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The battery you are considering<\/h4>\n