How this calculator works
The energy cost and payback calculator converts a cold-room refrigeration load (in kW) into annual PKR electricity spend, compares two panel insulation options (Panel A vs Panel B), and computes simple payback period and 25-year net-present-value of the upgrade. Annual energy consumption is calculated as: load (kW) × annual run-hours × system COP−1. Run-hours default to 8,000 h/year (22 h/day × 365 days) — adjustable by the user. COP defaults use ASHRAE Handbook — HVAC Systems and Equipment typical values for the entered temperature class. Electricity tariff defaults follow NEPRA WAPDA ToU industrial tariff and K-Electric (KEL) industrial peak/off-peak schedule, updated to the latest gazette notification. Payback = (capital cost difference) ÷ (annual energy saving). NPV uses a 10 % real discount rate and 6 % annual energy price escalation (Pakistan 10-year average). Results are indicative; actual savings depend on occupancy pattern, WAPDA load-shedding uplift, and installed equipment COP.
References: ASHRAE HVAC Systems and Equipment Handbook 2020; NEPRA Determination on WAPDA Industrial Tariff; K-Electric Tariff Schedule B3.