Plan site batteries with confidence. Compare kW or kVA loads. Add real deratings and reserves. Get kWh, Ah, and module counts. Export results.
| Load (kW) | Duration (h) | DoD (%) | Efficiencies (%) | Reserve (%) | Nominal Required (kWh) |
|---|---|---|---|---|---|
| 15.0 | 4.0 | 80 | Inv 92, RT 90 | 10 | ~95.2 |
| 8.5 | 6.0 | 85 | Inv 94, RT 92 | 15 | ~75.0 |
| 25.0 | 2.5 | 75 | Inv 90, RT 88 | 10 | ~105.5 |
This calculator sizes nominal storage so the usable energy meets demand.
Accurate inputs lead to safer, smarter on-site energy planning.
Construction sites depend on temporary power for cranes, hoists, lighting towers, dewatering pumps, HVAC commissioning, site offices, and digital tools. When grid supply is unstable or generators must be limited for noise and emissions, an energy storage system can bridge gaps, shave peaks, and support critical loads. The key is converting a mixed, real-world demand profile into a practical storage capacity that remains usable after losses, operating limits, and degradation.
Start by defining your essential loads and the time window you must cover. If your power data is listed in kVA, convert to kW with power factor to reflect real energy usage. Next, apply conversion losses from the inverter, internal charge–discharge losses (round-trip efficiency), and operational limits such as depth of discharge. Finally, account for temperature impacts and a reserve margin for aging, future load growth, and unexpected duty cycles.
This calculator uses those elements to estimate nominal storage. Nominal capacity is higher than usable capacity because the system cannot deliver every stored kilowatt-hour to the load. By using conservative derating and reserve values, you reduce the risk of shortfalls that can stall concrete pours, interrupt curing control, or delay safety systems. The output in amp-hours helps translate energy needs into a battery bank at a chosen DC bus voltage.
Module planning is optional but useful for early procurement. Enter module voltage and either module amp-hours or module energy. The calculator estimates series modules needed to reach the system voltage and the parallel strings required to meet the nominal energy target. Always confirm final design with manufacturer limits for current, thermal performance, protection devices, and installation codes.
Suppose a site needs 15 kW for 4 hours. Use inverter efficiency 92%, round-trip efficiency 90%, depth of discharge 80%, temperature derating 95%, and aging reserve 10%. The load energy is 60 kWh. The usable multiplier is 0.92×0.90×0.80×0.95×(1−0.10) ≈ 0.566. Nominal required storage is 60/0.566 ≈ 106.1 kWh. At 48 V, that is about (106.1×1000)/48 ≈ 2210 Ah.
Use the CSV and PDF exports to document assumptions for stakeholders, compare scenarios, and keep a clear sizing trail throughout planning, tendering, and commissioning. Good sizing improves reliability and cost control.
1) Why is nominal capacity higher than load energy?
Nominal capacity includes losses and limits. Inverter losses, round-trip losses, depth limits, temperature derating, and reserve margins reduce usable energy, so the stored amount must be larger.
2) Should I size using kW or kVA?
Use kW when you know real power. Use kVA when equipment is nameplated in apparent power, then apply power factor to convert to kW for energy calculations.
3) Does surge factor change the kWh result?
Surge affects inverter power rating and current capability, not total energy. Energy is primarily kW times hours, adjusted by efficiencies and limits.
4) What depth of discharge should I choose?
Choose values aligned with the technology and warranty. Conservative DoD can extend life but increases required nominal capacity. Follow manufacturer recommendations and project duty cycle.
5) How do temperature conditions affect capacity?
Cold and extreme heat can reduce deliverable capacity. Use derating that reflects enclosure, ventilation, and expected site temperatures to avoid shortfalls during critical operations.
6) How accurate is the module count estimate?
It is a planning estimate. Final counts depend on allowable currents, balancing, protective devices, and exact module specifications. Verify series/parallel limits with the selected product.
7) What reserve margin is reasonable for construction sites?
Many teams start around 10–20% for aging and growth, then refine using measured load logs. Higher uncertainty or long schedules may justify more reserve.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.