15+ years • 6,500+ jobs completed • 1,500+ Oklahoma homes served
Straightforward pricing
- $99 dispatch on every truck roll. Free on new-install estimates.
- $210 flat residential service call: $99 dispatch plus $111 diagnostic. The diagnostic does not reduce the repair price.
- Written repair estimate: I give you a written repair estimate before repair work starts.
- Free estimates on new installs. No charge to walk through replacement options.
Call (405) 375-4822. 4.8 stars, 300+ Google reviews.
HVAC System Sizing Calculator
Tell me about your home and book a free in-home sizing check. 4.8 stars, 300+ reviews.
I’m Dave Hartzell. I’ve been sizing HVAC systems in Central Oklahoma for 47 years. Fill this in so I know what I am looking at, then call me at (405) 375-4822 for a free in-home sizing check before you buy anything. I run a heat load calculation before I size a system.
No guessing here. I do not print a tonnage on a web form, because a screen cannot see your attic, ductwork, windows or which way the house faces. Wrong tonnage costs more in comfort, humidity, and energy than the equipment itself. Call (405) 375-4822 for a free in-home sizing check.
How sizing works
I do not print a tonnage on this page. I run a heat load calculation before I size a system. For a home that is an ACCA Manual J, and for each apartment in a multifamily building I run it unit by unit. For a shop, office, daycare or barbershop I use a commercial load calculation that counts people, lighting, equipment and the fresh air the space requires. For a window unit, the ENERGY STAR room air conditioner sizing chart is the guide to use. A real calculation pulls infiltration rates, exact window areas and orientations, wall R-values, and duct losses. A square footage guess never does.
Why right-sizing matters
In a humid climate like Oklahoma, oversized AC is worse than slightly undersized. Too big means short cycles, no humidity removal, clammy walls, and a compressor that wears out years early. I’ve ripped out oversized units that should have been a ton smaller. Right-sized runs longer, dehumidifies properly, and lasts 15 plus years.
Frequently asked questions
How many tons of AC do I need in Oklahoma?
In Oklahoma’s mixed-humid climate, do not take a tonnage off a web page. Insulation, sun exposure, window count, ceiling height and ductwork all swing the answer, which is why I run a heat load calculation before I size a system. Call 405-375-4822 for a free in-home sizing check.
What is a Manual J load calculation?
Manual J is the industry-standard heat load calculation published by ACCA. It accounts for every wall, window, door, ceiling, floor, infiltration rate, internal gain, and orientation in your home. It’s the right way to size an HVAC system. The in-home sizing check is free for Kingfisher and Central Oklahoma customers.
Why is over-sizing my AC bad?
An oversized AC cools too fast to pull humidity out of the air, so you end up with a cold clammy house. Short cycling also wears compressors out early and burns more electricity. Right-sized is better than bigger, every time.
Does Hartzell’s do load calcs?
Yes. I run a heat load calculation before I size a replacement system, and the in-home sizing check is free. I have been doing HVAC 47 years. Call (405) 375-4822.
Ready for a real Manual J?
Free in-home load calculation. No pushy sales pitch. Just the right size.
Hartzell’s Heat & Air, 602 S Main St, Kingfisher OK. 4.8 stars, 300+ reviews.