Example Data Table
| Input |
Geothermal Example |
Air Heat Pump Example |
Meaning |
| Heating load |
55 MMBtu |
55 MMBtu |
Annual delivered heating demand |
| Cooling load |
18 MMBtu |
18 MMBtu |
Annual delivered cooling demand |
| Heating COP |
4.2 |
2.8 |
Heat moved per unit of electricity |
| Cooling EER |
28 |
15 |
BTU moved per watt hour |
| Installed cost |
$34,000 |
$14,500 |
Before incentives |
Formula Used
Heating electricity: Heating kWh = Heating MMBtu × 293.071 ÷ heating COP.
Cooling electricity: Cooling kWh = Cooling MMBtu × 1000 ÷ EER.
Pump or fan electricity: kWh = watts × hours ÷ 1000.
Annual operating cost: Cost = total kWh × electric rate + annual maintenance.
Net installed cost: Net cost = installed cost − incentives.
Simple payback: Payback = extra geothermal net cost ÷ annual operating savings.
Net present value: NPV = present value of yearly savings − extra upfront cost.
Emissions: CO2e = total kWh × grid emission factor.
How to Use This Calculator
- Enter annual heating and cooling loads from an audit or model.
- Add your electric rate and local grid emission factor.
- Enter geothermal COP, EER, loop pump use, and installed cost.
- Enter air heat pump COP, EER, fan use, and defrost penalty.
- Add incentives, maintenance costs, discount rate, and escalation rate.
- Press Calculate to compare energy, cost, payback, and emissions.
- Use CSV or PDF buttons to save the calculated result.
Geothermal and Air Heat Pump Planning
A geothermal unit uses stable ground temperature as its source. An air heat pump uses outdoor air. Both move heat instead of making heat directly. That is why the coefficient of performance matters. A higher COP means less electrical input for the same delivered heat.
Main Cost Drivers
The largest geothermal cost is the ground loop. It can be vertical, horizontal, pond based, or open loop. The largest air source cost is usually the outdoor unit and indoor coil. Air systems are easier to install. Geothermal systems often last longer in the ground loop portion. The calculator separates equipment cost, incentives, maintenance, and power cost. This helps you compare the real project difference.
Physics Behind the Estimate
The heating load is converted from million BTU to kilowatt hours of heat. That heat is divided by COP. Cooling load is divided by the rated cooling efficiency. EER is expressed as BTU per watt hour. Fan, loop pump, auxiliary heat, and defrost penalties are added after the main load calculation. This gives a more practical annual electricity estimate.
Financial View
Simple payback uses the extra geothermal investment divided by annual savings. Discounted payback is stricter. It reduces future savings by a discount rate. Energy price escalation can raise future savings each year. Net present value compares the present value of savings with the extra initial cost. A positive value means the geothermal choice can be financially stronger over the selected period.
When Geothermal Wins
Geothermal usually performs well in climates with long heating seasons. It also helps where electricity prices are high. It can be attractive when incentives reduce the loop cost. It may be weaker when drilling is expensive or the home load is small. Air source systems can win when upfront budget is limited. Modern cold climate units can be very competitive.
Good Input Practice
Use annual loads from an energy audit when possible. Avoid using equipment size alone. Oversized units may hide the real seasonal demand. Check electric bills for rate accuracy. Enter realistic maintenance costs. Compare several COP and EER values. Small changes can shift payback. Use the result as an estimate, not a final bid. Review quotes before choosing any system.
FAQs
1. What does this calculator compare?
It compares a geothermal heat pump with an air heat pump. It estimates annual electricity, operating cost, installed cost, payback, net present value, and emissions.
2. Is geothermal always cheaper to run?
Usually it uses less electricity because ground temperatures are stable. Still, pump power, loop design, load size, and electric rates can change the result.
3. Why is geothermal installation cost higher?
The ground loop adds drilling, trenching, piping, flushing, and design cost. The loop can last a long time, but it raises the upfront investment.
4. What is COP?
COP means coefficient of performance. A COP of 4 means the system moves four units of heat for each unit of electrical input.
5. What is EER?
EER means energy efficiency ratio. It shows cooling BTU moved per watt hour. A higher EER means lower cooling electricity use.
6. What is the defrost penalty?
Air heat pumps may lose efficiency in cold weather. Defrost cycles and auxiliary heat can increase electricity use. This field adds that penalty.
7. Why use net present value?
Net present value discounts future savings. It helps compare a high upfront cost with savings that arrive over many years.
8. Should I use bid data?
Yes. Use contractor quotes, utility rates, audit loads, and local incentives. Better inputs make the estimate more useful for real decisions.