Time for a new furnace and you’re wondering what capacity unit you’ll need? You’ve come to the right place. While you’ll want to consult with a qualified HVAC professional before making your final decision, our furnace size calculation guidelines can give you a good idea of what you’ll want to be shopping for.
The most accurate and recommended method of determining your furnace size is to have professional perform a heat loss calculation following ACCA or ASHRAE guidelines. Most heating contractors have the software to perform such a calculation and they can work with a set of plans or perform the calculations on-site. If you’d like to get a rough idea of your heating needs there are some rule-of-thumb numbers you can use.
Of course, heating capacity needs vary by climate, so the following rules-of thumb values are specific to the Upper Midwest.