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Homeowner's guide to:

Oil Central Heating

Fuel Oil Furnace and Boiler Sizes

Step 1: Using the map below, find your climate zone’s Required Heating Power, measured as BTUs per Square Foot.

Step 2: Using the Correction Factor table below, find your home’s Correction Factor.

Step 3: Multiply your home’s square feet by the Required Heating Power (from Step 1), and multiply that by the
Correction Factor (from Step 2) to find your recommended boiler size.


Correction Factor

For a building that you know has adequate insulation – No adjustment needed

For a building that has no insulation – Multiply BTU Requirements x 1.15

For a building in severe conditions only – Multiply BTU Requirements x 1.61

Other Considerations

  • Air Infiltration: A drafty building is hard to heat. Make sure there are no gaps in the doors or windows of the building.
  • House Floorplan: In general, it is harder to heat longer, narrower homes than shorter, squarer homes.
  • Ceiling Height: If the ceiling is more than 14’ high, install ceiling fans to re-circulate the heat from the ceiling down onto the floor area.
  • Heat Recovery: If the garage doors are left open a lot or opened and closed frequently you may need a more powerful heating unit. (Clean Burn)