Insights ·
More batteries don't mean more savings: a real 3.0TD tariff
“Add more batteries and you'll save more.” It's the most expensive sentence in Spanish energy storage. And it's false.
“Add more batteries and you'll save more.”
It's the most expensive sentence in Spanish energy storage. And it's false.
We ran the numbers with the real 3.0TD tariff of a Madrid restaurant, the one any three-phase business pays. Arbitrage (charge cheap at night, discharge expensive by day) depends on one thing only: the price gap between the charging hour and the discharging hour. And that gap, month by month, is this:
- January, February, July, December: 8.0 cents/kWh
- March, November: 5.1 cents
- June, August, September: 1.5 cents
- April, May, October: 0.3 cents
The figure nobody puts in the quote
A battery with its inverter loses 10-12% of the energy on every round trip. With the off-peak price at ~11 cents, that means you need a minimum spread of ~1.2 cents just to break even.
Look at the table again: in 6 of the 12 months, pure arbitrage loses or breaks even.
Consequence: battery no. 5, no. 6, no. 8 in an oversized quote save nothing, they fill and empty for nothing half the year, burning cycles of life.
So where do the savings come from?
Where does a battery's real saving come from in a Spanish business?
- Backup: not losing the cold room or the till in the next blackout (April 28 cost hospitality more than any bill).
- Power optimization: no more excess penalties, right-sized contracted power.
- Reactive power: the inverter compensates it for free.
- And arbitrage only in the months it's worth it: with the battery you need, not the one someone wants to sell you.
Sizing right isn't selling less. It's the customer coming back.