A battery datasheet gives two numbers: power in kW and capacity in kWh. On their own they mean little. They only make sense next to how your site uses electricity. Too small, and you leave savings on the table. Too large, and capital sits in cells that rarely cycle. Before we propose a configuration and a price, we look at four things.
Guide · Battery storage
How to size battery storage for your business
A good battery offer starts with your consumption data, not with a product. Here is what we look at, and what to have ready.
1. Start with the load profile, not the annual bill
Annual consumption tells us how much energy the site uses. It does not tell us when, and for sizing a battery the timing matters more than the total.
The most useful data is the 15-minute load profile from your electricity meter, ideally for a full year. Most medium and large business connections have interval metering, and the data is available from your distribution system operator, usually through its customer portal or on request. If you only have monthly invoices, we can still estimate, but with a wider margin.
2. Decide what the battery is for
The job sets the size. Most sites combine two or three of these, and the sizing has to satisfy the most demanding one.
- Using more of your own solar. The battery stores the midday surplus your site cannot use at the time and releases it in the evening. On a typical sunny day, the energy your panels send to the grid is a good first estimate of the capacity worth storing.
- Cutting peaks. The battery covers short spikes in demand so that your draw from the grid stays below a set level. Its power must cover the gap between the peak and that level, and its capacity must last as long as the peak does.
- Backup power. The battery carries the loads that must keep running during an outage. Capacity follows from the critical load and the runtime you need.
- Buying cheap, using later. The battery charges when electricity is cheap and discharges when it is expensive. The price spread and the number of cycles decide the return.
3. Power and capacity are separate decisions
Power, in kW, is how fast a battery can charge or discharge. Capacity, in kWh, is how much energy it holds. The ratio between the two depends on the job.
The farm in Žarnov uses 60 kW and 120 kWh: two hours at full power, enough to move midday solar into the evening. The research station in Gabčíkovo uses 125 kW and 1,305 kWh, because it has to carry its equipment for many hours if the grid fails. Same product family, very different ratios.
Typical ratios
- Capacity divided by power = hours at full output
- Self-consumption: often 2 to 4 hours
- Peak shaving: often 1 to 2 hours
- Backup: as many hours as the outage you plan for
4. Check the site before choosing the battery
An engineer looks at the existing inverter, the main switchboard, the grid connection agreement and the reserved capacity. Adding storage to a working photovoltaic system is usually possible without touching the panels: in Žarnov, the battery was connected to an installation that had been running for years.
Location matters too. Outdoor cabinets need a level base, service access and the clearances required by the manufacturer and fire safety rules. Indoor systems need a suitable room with ventilation and fire protection designed in from the start.
What you get back
We model the site hour by hour and propose a configuration: power, capacity, the expected share of self-supplied energy, the savings and the payback. You receive a sizing proposal within a week of sending the data.
If something is missing, we tell you what and why, rather than filling the gap with assumptions.
What to send us
- 15-minute load data for the last 12 months, or your monthly invoices
- Connection details: reserved capacity, main breaker, voltage level
- Your photovoltaic system: size, inverter model, yearly production
- What the battery should do, and which loads must stay on in an outage
- A site plan or photos of where the battery could stand
Questions we hear
Only roughly. The annual figure does not show when you use energy, and timing is what decides how much a battery can shift. A year of 15-minute data gives a far more reliable result.
No. Capacity that rarely cycles still has to be paid for. We size to the use you actually have, and modular systems can be extended later if your consumption grows.
It depends on the use. Self-consumption and price arbitrage usually mean about one full cycle a day. The LFP batteries we use are rated for 6,000 to 8,000 full cycles, depending on the system.
No. A battery can cut peaks, provide backup or charge when electricity is cheap on its own. With solar on site it also stores your own production, which usually shortens the payback.
Free sizing proposal
See what storage would save on your site
Send us your consumption data and the size of your photovoltaic system, if you have one. We come back with a configuration and a price.
✓ We reply the next working day
✓ Sizing proposal within a week
✓ No obligation, no sales pressure
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