Converting an Oil Boiler to Geothermal in Arlington, MA

In 2025, EnergySmart Alternatives completed a geothermal retrofit at a 2,200-square-foot home built in 1978 in Arlington. The property was originally heated with an oil boiler and cooled with a traditional central air conditioning system.

The homeowners wanted to transition away from fossil fuels and take advantage of renewable energy. By replacing the existing heating and cooling system with a high-efficiency geothermal heat pump, EnergySmart helped the homeowner significantly reduce energy costs while creating a quieter, more efficient home comfort system.

This project demonstrates that geothermal systems aren’t just for new construction; they can also be an excellent upgrade for modern homes looking to improve efficiency and sustainability.

Why This Home Was a Strong Candidate for Geothermal

Several factors made geothermal an ideal solution for this retrofit project.

The Homeowner Wanted to Eliminate Fossil Fuel Use

The homeowner was looking for a long-term solution that would reduce dependence on natural gas and move the home toward cleaner energy.

Aging Air Conditioning Equipment

The existing air conditioning system was installed in 2010. The age of the AC system made it a logical time to consider upgrading to a more efficient system that could provide both heating and cooling.

Adequate Space for Drilling

The property had sufficient space in the side yard to install the vertical boreholes needed for the geothermal loop system.

Installation Overview

To install the geothermal system, EnergySmart drilled two 6-inch diameter vertical boreholes in the side yard of the property. These boreholes serve as the underground heat exchange system that allows geothermal heat pump technology to transfer heat between the home and the earth.

High-density polyethylene (HDPE) geothermal piping was installed inside each borehole and sealed in place using geothermal grout to ensure long-term durability and efficient heat transfer.

The loop pipes were then brought into the home through two 3-inch core penetrations in the concrete foundation. Inside the mechanical space, the geothermal loops were connected to a variable-speed geothermal heat pump, which was flushed with an ethanol-based antifreeze solution to maintain safe operation during colder temperatures.

One of the advantages of this retrofit was the ability to reuse the home’s existing HVAC infrastructure. A second heating and cooling zone was added to the basement for improved comfort.

Modern heat pump thermostats were installed with WiFi connectivity, allowing the homeowner to monitor system performance and control temperatures remotely through a mobile app.

System Performance and Operating Costs

The geothermal system has delivered strong performance while dramatically improving energy efficiency.

• First Year Electricity Use (May 2025 to May 2026): approximately 3,900 kWh
• Estimated Operating Cost: about $1,200 per year at $0.30/kWh

For homeowners looking to reduce both energy bills and carbon footprint, installing a geothermal system can create a powerful high-efficiency energy solution.

Benefits of Switching from Gas to Geothermal

This retrofit provided several immediate and long-term advantages for the homeowner.

One System for Heating and Cooling

A single geothermal heat pump now provides both heating and air conditioning, eliminating the need for separate systems.

Fossil Fuel Heating Eliminated

The oil boiler is no longer needed, reducing reliance on fossil fuels and lowering emissions.

Quieter Outdoor Environment

The traditional outdoor AC condenser was removed, eliminating the noise typically associated with central air conditioning.

Improved Comfort and Efficiency

Variable-speed geothermal heat pumps provide steady temperature control, better humidity management, and improved overall comfort compared to traditional systems.

Remote Monitoring and Control

WiFi-connected thermostats allow homeowners to monitor energy usage and adjust temperatures from anywhere.

A Smart Upgrade for Homeowners Looking to Move Beyond Oil Heat

This Arlington geothermal retrofit demonstrates that homeowners don’t need to wait for a new construction project to enjoy the benefits of geothermal heating and cooling. By replacing an aging oil boiler and conventional air conditioning system with a high-efficiency geothermal heat pump, the homeowners were able to reduce their reliance on fossil fuels, improve year-round comfort, and lower their long-term operating costs.

With annual geothermal electricity usage of just 3,900 kWh and estimated heating and cooling costs of approximately $1,200 per year, this project highlights the significant efficiency gains that geothermal technology can provide. The addition of a new basement zone also improved comfort throughout the home while making better use of the existing HVAC infrastructure.

For Massachusetts homeowners facing the replacement of an oil boiler, furnace, or aging air conditioning system, geothermal can be an attractive alternative that provides heating and cooling from a single system while delivering decades of reliable performance.

EnergySmart Alternatives specializes in geothermal retrofits for existing homes throughout Massachusetts. If you’re considering replacing an older heating or cooling system, our team can evaluate your property and help determine whether geothermal is the right solution for your home.