Solar Arbitrage Value Calculator

Shift cheap energy to peak hours automatically daily. Compare rates, battery size, and efficiency fast. See annual savings, payback, and lifetime value estimates instantly.

Inputs

Nameplate energy rating of the storage system.
Usable fraction after reserve and limits.
Charging-to-discharging delivered efficiency.
Typical full or partial cycles per day.
Operating days (often 365 for sites).
Energy price during high-cost hours.
Energy price used for charging periods.
AC charging limit (inverter or site limit).
Hours available to charge at off-peak.
AC discharge limit during peak window.
Peak period duration you can target.
Optional. Enter 0 if not applicable.
Average monthly reduction you can sustain.
Capacity fade applied each year.
Maintenance, software, inspections, warranties.
Installed project cost used for NPV and payback.
Used for present-value calculations.
Analysis period for lifetime value.
Tip: If your peak window is short, power limits may cap usable energy.

Example data table

Scenario Battery (kWh) Usable depth (%) Efficiency (%) Peak/Off-peak ($/kWh) Cycles/day Demand ($/kW-mo) & kW Capex ($)
Small site office 60 90 88 0.28 / 0.12 1.0 10 & 15 45,000
Medium construction yard 150 90 90 0.32 / 0.14 1.0 18 & 35 95,000
High-peak utility schedule 300 85 92 0.40 / 0.10 1.2 25 & 60 180,000
Use your site tariff and realistic peak reduction values.

Formula used

1) Usable energy per cycle

usable_kWh = battery_kWh × (usable_depth% ÷ 100)

cycle_charge_kWh = min(usable_kWh, charge_kW × charge_hours, discharge_kW × discharge_hours)

Power windows can limit energy even with a large battery.

2) Energy arbitrage savings

cycle_discharge_kWh = cycle_charge_kWh × (efficiency% ÷ 100)

annual_charge_kWh = cycle_charge_kWh × cycles_per_day × days_per_year

energy_margin = (peak_rate × efficiency) − offpeak_rate

annual_energy_savings = annual_charge_kWh × energy_margin

3) Demand charge savings

annual_demand_savings = demand_rate × kW_reduction × 12

This assumes you can reliably reduce measured monthly peak demand.

4) Degradation and NPV

capacity_factor(y) = (1 − degradation%)^(y−1)

net_cashflow(y) = (annual_energy_savings × capacity_factor) + annual_demand_savings − O&M

NPV = −capex + Σ net_cashflow(y) ÷ (1 + discount_rate)^y

Use consistent units: kW with hours gives kWh, and rates are in $/kWh.

How to use this calculator

  1. Enter your storage capacity and usable depth based on limits.
  2. Set charge and discharge power plus realistic time windows.
  3. Add peak and off-peak energy rates from your tariff.
  4. If applicable, add demand charges and expected kW reduction.
  5. Include annual O&M, capex, degradation, discount rate, and life.
  6. Press Calculate to view results above the form.
For construction sites, verify generator integration rules and peak measurement timing. If export is compensated differently, treat peak_rate as avoided cost.

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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.