Added heating gas cost calculator

Lost lighting heat must be replaced by the heating system during heating hours.

Units

C_{\text{heat}} = \frac{\Delta \mathrm{kW} \times H_{\text{heat}} \times 0.003413 \times r_{\text{gas}}}{\eta_{\text{heat}}}

Calculator

Enter the values you know and leave one box empty. Calculate finds the empty one, the result or any input.

Given

C_{\text{heat}} = \frac{12 \times 2500 \times 0.003413 \times 9}{0.8} \approx 1{,}152

Symbol	Meaning	Unit
$C_{\text{heat}}$	added yearly gas cost	$/yr
$H_{\text{heat}}$	equivalent heating hours	h/yr
$\eta_{\text{heat}}$	heating efficiency as fraction	—
$r_{\text{gas}}$	gas rate at the assumed heating value	$/MCF
$\Delta \mathrm{kW}$	lighting heat reduction	kW

Symbol	Meaning	Unit
$C_{\text{heat}}$	added yearly gas cost	$/yr
$H_{\text{heat}}$	equivalent heating hours	h/yr
$\eta_{\text{heat}}$	heating efficiency as fraction	—
$r_{\text{fuel}}$	fuel-energy price	$/kWh fuel
$\Delta \mathrm{kW}$	lighting heat reduction	kW

Results are estimates for study and screening. Check the inputs, units and assumptions before you use them for design, billing or contract decisions.