This article breaks down the mathematical calculations used in higher SEER HVAC replacement savings calculator
To calculate the energy reduction with HVAC replacement using a higher SEER rating, start by converting the cooling capacity into the electrical power required. Each ton of cooling capacity equals 12,000 BTU per hour. The electrical power draw (in kilowatts, kW) for a given SEER can be calculated with the formula:
$$ \text{Power (kW)} = \frac{\text{Tonnage} \times 12000}{\text{SEER} \times 1000} $$
This formula converts the system’s cooling capacity (measured in tons) into the power draw by considering the efficiency of the system provided by the SEER rating.
After determining the power draw for the current system and the upgraded system, compute the reduction in power demand using:
$$ \text{Demand Saved} = \text{Current Power} - \text{New Power} $$
With the difference in power consumption known, the next step is to calculate how much energy is saved over an entire year. Multiply the saved demand (in kW) by the number of operating hours per year:
$$ \text{Energy Saved (kWh/year)} = \text{Demand Saved} \times \text{Operating Hours per Year} $$
Next, if you know the cost of electricity, the energy cost savings are computed as:
$$ \text{Energy Cost Savings} = \text{Energy Saved} \times \text{Electricity Cost} $$
If your billing includes demand charges, calculate the demand cost savings by considering the cost per kilowatt over a 12-month period:
$$ \text{Demand Cost Savings} = \text{Demand Saved} \times 12 \times \text{Demand Cost} $$
The sum of these two gives the total annual cost savings:
$$ \text{Total Cost Savings} = \text{Energy Cost Savings} + \text{Demand Cost Savings} $$
For estimating the environmental impact, use the carbon intensity value (in lb-CO₂/kWh) along with the energy saved to calculate the CO₂ emission savings in tonnes (remembering that 1 tonne is equivalent to 2,205 pounds):
$$ \text{CO}_2 \text{ Emission Savings (tonnes/year)} = \frac{\text{Energy Saved} \times \text{Carbon Intensity}}{2205} $$
Finally, if there is an upfront implementation cost for the upgrade, the simple payback period in months can be determined by comparing this cost with the annual savings:
$$ \text{Simple Payback (months)} = \left(\frac{\text{Total Implementation Cost}}{\text{Total Cost Savings}}\right) \times 12 $$