A battery stores midday export for the evening and holds the peak down. How big it should be is a measurement: the kWh still exported once the loads that can move have moved, and the kW it has to take at once. Whether it pays for itself is your tariff's arithmetic, and we give you every figure that goes into it.
75% full on 65 weekdays a year, May to July. With nothing moved first it would need 470 kWh.
It charges from the export at midday and gives it back whenever the service would draw more than a set figure.
Kestrel Park Distribution, the specimen warehouse in the scrolled story, on a June weekday with its loads already moved.
The warehouse still exports 128 kWh on the weekday, so the battery is 130 kWh. The export never runs faster than 60 kW, so that is its rating.
It gives back 114 kWh through the evening and the morning start and holds the service at 55 kW. Sized before the loads moved, it would have been 340 kWh bigger.
A battery sized on a summer weekday does less in winter, and the year says how much less.
Each month's peak at the specimen warehouse, with its loads moved and with the battery.
A weekday's export charges the battery 75% full on 65 weekdays a year, May to July. In winter the moved loads use nearly all the array gives, and the battery has little to charge from.
87% of the export left in the year falls on closed weekends, when there is no evening load to give it to. Over the year the battery moves 9,607 kWh.
Each kWh the battery moves is worth the gap between what the utility credits at noon and charges at night.
Each kW off the month's peak is worth the charge per kW, in the months the battery fills.
What it costs fitted and the years it is warranted to cycle, set against the two above.
We size the kWh from the export that is left and the kW from the fastest it runs.
We size it again with nothing moved, so you see what moving the loads first is worth.
We run the battery on the measured day and read the peak and the export it leaves.
We write the charge and discharge rules the controller would run, signed by an engineer.
The battery's size and the day it was sized on, after the loads that can move have moved.
From the study's yearThe month's peak and export with the battery, against the same month without it.
Reviewed by an engineerCharge only from export, hold the month's figure, never export from the battery.
Signed by an engineerIt reads the year from a Self-Consumption Study and starts after Solar Load Shifting.
12 months of your utility's 15-minute interval data with its export channel, the inverter's production log, and your tariff. Where loads have not yet moved, the sizing is done both ways.
The battery is bought and fitted by your own contractor. Its charge and discharge run as fixed rules an engineer wrote and signed, on our controller, and Wattif performs no electrical work.
