How Much is Your Furnace Costing You?

How Much Does the Beast in the Basement Cost You?

In 1992, the federal minimum-efficiency standards for furnaces and chances are that its efficiency was only 55% to 65% when new. It's no longer new. Today, its efficiency is less than when it was new, due to performance degradation over time. If you have not been diligent about annual service, the performance degradation could be more.The Beast is a hungry beast. Find out how much it's eating out of your household budget and compare the savings from a furnace or boiler. All you need is a calculator, old utility bills, and this worksheet. If you do not have the utility bills, make your best estimate.

1. Determine Your Annual Fuel Costs

The first step is to identify how much you spend on gas or fuel oil annually.

Add up 12 months of gas/oil bills - OR - Estimate your average monthly gas/oil cost and multiply by 12

2. Determine Your Base Load Fuel Usage

Your furnace or boiler does not use all of your fuel. Some is used for hot water, cooking, and other tasks. This is the "base load" and can be determined from your lowest bill, which is typically a Summer bill when your heating system was not operating.

Find or estimate your lowest monthly fuel bill and multiply by 12:

3. Calculate Your Heating Costs

By subtracting the base load from the total fuel costs, you can identify how much you spend on heating each year.

Subtract the base load from the total fuel costs:

4. Estimate the Impact of Rising Fuel Prices (Optional)

Fuel prices are not static. Gas prices are expected to rise this year, possibly dramatically. You must take rising prices into account.

Estimate the percentage increase in gas or fuel oil:

Multiply the heating costs by (1 + % fuel increase):

5. Estimate the Efficiency of Your Furnace or Boiler

Remember, your heating system is not the same efficiency it was when it was new. You should account for the performance degradation.

Use the table below to estimate efficiency if unknown…

Efficiency Table
Date of Manufacture Efficiency
Before 1992 55% - 65%
On or After 1992 78% - 80%

Enter the efficiency of the furnace or boiler when new:

Use the table below to select the degradation factor (optional)…

Estimated Degradation Table (Optional)
Furnace Age
6 to 10 Years
11 to 15 Years
16 to 20 Years
21 to 25 Years
26 to 30 Years

Multiply the efficiency when new by the degradation factor:

6. Compare the Cost of Ownership with a New Heating System

To determine the fuel cost for a new furnace multiply the fuel cost by the current heating system's efficiency and divide this by the new system's efficiency (e.g., New Fuel Cost = Current Fuel Cost X Current Efficiency / New Efficiency)

  Current System   Mid-Efficiency (78% to 80%) Cost Savings     5 Year Savings
Efficiency   -     = X 5 =  
Heating Fuel Cost   -     = X 5 =  
+ Today's Repair   - $0.00   = X 5 =  
= Ownership Cost   -     = X 5 =  
  Current System   Mid-Efficiency (90% to 97%) Cost Savings     5 Year Savings
Efficiency   -     = X 5 =  
Heating Fuel Cost   -     = X 5 =  
+ Today's Repair   - $0.00   = X 5 =  
= Ownership Cost   -     = X 5 =  

Note: With today's financing, it is possible that your monthly savings will exceed your payments.

© 2003 Service Roundtable

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