Solar + Storage (Commercial) Calculator

Demand charge reduction from battery dispatch strategy.

Solar capacity (kW DC)

Battery capacity (kWh)

Battery power (kW)

Current peak demand (kW)

Demand charge ($/kW/mo)

Energy rate ($/kWh)

Peak sun hours (PSH)

Battery round-trip efficiency

Solar cost ($/W DC)

Battery cost ($/kWh)

Tab to move between fields

Total annual savings ($)

$56,248.00

≈ 5 years of state college

Peak demand reduction (kW)160

New peak demand (kW)140

Annual demand savings ($)$28,800.00

Annual energy savings ($)$27,448.00

Annual solar production (kWh)292,000

Total system cost ($)$380,000.00

Simple payback (years)6.8

Battery duration (hours)4

How to Use This Calculator

Enter solar capacity in kW DC and battery capacity in kWh with rated power in kW.
Input current peak demand in kW and demand charge rate per kW per month from your utility bill.
Set energy rate per kWh and peak sun hours.
Enter solar cost per watt and battery cost per kWh.
Review annual demand savings, energy savings, simple payback, and battery duration to size the system.

How the result changes with Solar capacity (kW DC)

Solar capacity (kW DC): Installed solar DC capacity.
Battery capacity (kWh): Usable battery energy capacity.
Battery power (kW): Maximum battery charge/discharge rate.
Current peak demand (kW): Building's current monthly peak demand from utility bill.
Demand charge ($/kW/mo): Monthly demand charge rate from utility tariff.
Energy rate ($/kWh): Average commercial electricity energy rate.
Peak sun hours (PSH): Average daily peak sun hours.
Battery round-trip efficiency: Energy out / energy in. Lithium-ion: 85–92%.
Solar cost ($/W DC): Installed solar cost per watt.
Battery cost ($/kWh): Installed battery cost per kWh of usable capacity.

Total annual savings ($): Combined demand charge and energy savings per year.
Peak demand reduction (kW): kW shaved from monthly peak demand.
New peak demand (kW): Reduced peak demand after solar + storage.
Annual demand savings ($): Yearly savings from reduced demand charges.
Annual energy savings ($): Yearly savings from solar energy displacing grid purchases.
Annual solar production (kWh): Estimated solar electricity generated per year.
Total system cost ($): Combined solar + battery installed cost.
Simple payback (years): Years to recoup investment from savings (before incentives).
Battery duration (hours): Hours of discharge at rated power.

Identify Input Parameters
4 parameters
Solar capacity (kW DC) = 200, Battery capacity (kWh) = 400, Battery power (kW) = 100, Current peak demand (kW) = 300 = 10 input(s) provided
Calculate Total annual savings
Total annual savings = annualDemandSavings + annualEnergySavings
56248 = $56,248
Calculate Peak demand reduction
Peak demand reduction = min(
160 = 160
Calculate New peak demand
New peak demand = peakDemandKW - totalDemandReductionKW
140 = 140