HVAC Energy & Operating Cost Analyzer
Separate physical energy use, energy charges and demand charges, then compare an alternative HVAC scenario with tariff provenance.
Engineering example
Worked example checked against HVAC-ENERGY-001: thermal energy = 100 kW × 2,000 h × 0.5 load factor = 100,000 kWh. Compressor electricity = 100,000 / COP 4.0 = 25,000 kWh. Auxiliary electricity = 5 kW × 2,000 h = 10,000 kWh, because the load factor is not applied to auxiliary power. Electrical energy = 25,000 + 10,000 = 35,000 kWh/year. At 0.12 USD/kWh the energy charge is 4,200 USD. Peak demand for this example is P_peak = 100/4 + 5 = 30 kW. Monthly demand cost is C_d,month = 30 kW × R_d. Annual demand cost is C_d = P_peak × R_d × N_months, with N_months the billing-month count you enter (default 12, allowed 1–12). Demand is omitted unless a sourced demand rate R_d is entered.
Method & limitations
Engine formulas: E_th,kWh = (Q_W/1000)·H·LF; E_comp = E_th/COP; E_aux,kWh = (P_aux,W/1000)·H; E_elec = E_comp + E_aux; P_peak,kW = Q_W/(1000·COP) + P_aux,W/1000; energy charge = E_elec × rate; C_d,month = P_peak × R_d; C_d = P_peak × R_d × N_months. N_months is the demand billing-month count (1–12). The result shows C_d,month and C_d separately so a monthly rate is not read as the annual demand cost. LF multiplies thermal cooling energy only. Auxiliary power stays constant over the operating hours. Tariff location, period, source and currency are required. This is site model HVAC-ENERGY-001 only. Schedules, weather, part-load maps, controls, tariff revisions, demand ratchets and measurements are outside the model.
Formulas, source and scope
Formula source: site model HVAC-ENERGY-001. No utility-tariff standard edition is cited.
FAQ
Why is auxiliary energy 10,000 kWh rather than 5,000 kWh in the 35,000 kWh example?
Load factor multiplies thermal cooling energy only. Auxiliary electricity is power × hours with no load factor: 5 kW × 2,000 h = 10,000 kWh. Compressor electricity is 25,000 kWh. The sum is 35,000 kWh.
When is demand included?
Only after you enter a demand rate R_d. Monthly demand cost is C_d,month = P_peak × R_d. Annual demand cost is C_d = P_peak × R_d × N_months, where N_months is the billing-month count (1–12, default 12). The page lists those two costs separately. The annual total adds C_d only when energy and demand tariffs use the same currency.