Buying advice
What size furnacedoes my home need?
Ask three contractors and you'll get three BTU numbers — because some measure and some guess. Here's how furnace sizing actually works, the rules of thumb worth knowing, and why bigger is genuinely worse.
The honest rule of thumb
- In Indiana's climate, most homes need roughly 30–45 BTUs per square foot
- A 1,500 sq ft ranch typically lands around 45,000–60,000 BTU
- A 2,500 sq ft two-story typically lands around 75,000–100,000 BTU
- Good insulation, new windows and sealed attics push you toward the low end
- Leaky older homes, vaulted ceilings and big window walls push you higher
Why oversizing backfires
- An oversized furnace heats the house too fast, then shuts off — over and over
- That short-cycling wears out ignitors, motors and boards years early
- Rooms end up with hot blasts and cold gaps instead of steady warmth
- You pay for capacity you never use — upfront and on every gas bill
- A slightly undersized unit actually runs more comfortably than an oversized one
Why it matters
How we
actually size it.
01
We measure, not guess
A proper load calculation accounts for your square footage, insulation, windows, ceiling heights, orientation and local weather data. It takes longer than a guess — and it's why our installs hold temperature evenly.
02
The existing furnace is a clue, not an answer
Half the furnaces we replace were oversized by the last contractor. We note what's there, then verify with the calculation instead of copying a mistake.
03
Cooling gets sized too
Furnaces are measured in BTUs; air conditioners in tons. We size both — and as a residential and light commercial shop, we work on systems 5 tons and under, which covers virtually every home in the county.
Free quotes,
honest numbers.
Replacing a furnace this year? We'll measure your home and give you a straight answer on size and price. Go Dutch Rewards members save 15% on every repair, forever — and the card is free.
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