St. George, Utah · Booking service
AC installation and replacement in St. George
The most expensive HVAC decision most homeowners make, in the hardest cooling climate in Utah. Here is what actually matters before you sign anything.
- We book the appointment
- A licensed contractor does the work
- You contract directly with them
Sizing is the whole game here
Washington County's cooling design temperature. That is the 1% summer design figure listed for this county in RESNET's Appendix A, drawn from the ASHRAE 2017 Handbook of Fundamentals. Salt Lake County's is 96°F. Utah County's is 92°F.
A thirteen-degree gap sounds small. It is not. It is the difference between equipment that holds temperature on a July afternoon and equipment that runs flat out from noon and never catches up. Sizing rules of thumb carried down from the Wasatch Front undersize systems here, and a system that is undersized for the design day cannot be fixed with a thermostat setting.
The lazy way to replace a system is to read the tonnage off the old unit and put the same thing back. That carries forward whatever mistake was made the first time, and in older St. George housing stock the first time was often decades ago, before the windows were replaced, before the attic was re-insulated, and sometimes before the addition on the back existed.
What you want instead is a room-by-room load calculation — ACCA Manual J is the industry standard — run against this county's design conditions rather than a statewide average. Ask for it. A contractor who has done one can show you the output.
Oversizing is its own failure, and it is a real risk when someone overcorrects for the heat. A system too large for the house satisfies the thermostat fast, shuts off, and never runs long enough to pull humidity or to even out temperature between rooms. You get cold spots, short cycling, and compressor wear. The target is equipment matched to the actual load at the actual design temperature, not the biggest thing that fits the pad.
Questions worth asking before you sign
- Did you run a Manual J load calculation, and can I see it? If the answer is a tonnage number and no paperwork, that is not a load calculation.
- What design temperature did you calculate against? You are listening for something near this county's figure, not a number borrowed from northern Utah.
- Are you pulling the mechanical permit, and is that on the contract?
- What is your DOPL licence number? Then go and check it yourself.
- Is the ductwork sized for the new equipment? New equipment on undersized duct is a common way to buy capacity you never actually receive.
- What happens to the old refrigerant and equipment?
Permits and inspection in St. George
Utah builds on the State Construction Code, and St. George City's building code chapter adopts the construction codes the state has adopted. A changeout is not a repair — replacing the primary heating or cooling equipment is mechanical work, and the gas connection, venting and electrical all get looked at against current code rather than against whatever was acceptable when the original unit went in.
St. George City takes building permit applications through its online CityInspect portal at stg.cityinspect.com, and you need an account to file. A licensed contractor normally pulls the mechanical permit as part of the job. Ask before work starts whether the permit is being pulled and who is pulling it, and get the answer in writing on the contract.
If your address is outside city limits — much of the county is — the permit goes through Washington County rather than St. George City. The ZIP you give us is also what tells us which jurisdiction you are in.
Verify current requirements with the St. George City Building Department at 435-627-4100 before relying on any of this for a specific project.
How to check the contractor's licence yourself
Utah licenses heating and cooling contractors through the Department of Commerce, Division of Professional Licensing. The classification to look for is H100 — HVAC. DOPL's current contractor classification list no longer carries the older S350 HVAC specialty; new HVAC applications moved to H100, with the updated application requirements taking effect 20 April 2026.
Under the current requirements an H100 applicant has to complete a 25-hour pre-licensure course, pass the H100 written trade exam, and document 4,000 hours of qualified HVAC employment within the past five years using W-2s, K-1s or tax returns. DOPL also sets general liability insurance minimums for the classification, and a fingerprint-based background check requirement begins 1 January 2027.
You do not have to take anyone's word for it, including ours. Utah publishes a free licence lookup: secure.utah.gov/llv. Search the business name before work starts.
Utility programmes worth knowing about first
Two different electric utilities serve this area, and they run completely different programmes. Which one bills you determines what is available, so check your bill before you start shopping equipment.
Dixie Power
Dixie Power runs a residential heat pump rebate, and there is one detail on it that catches people out: it is a new construction programme. If you are replacing a system in a house that already exists, that particular rebate is not the one for you, whatever a salesperson tells you. The requirements also specify a minimum two-ton electric heat pump with electric backup or dual fuel.
Their smart thermostat rebate has its own conditions — you have to be on the Time of Day Optional Rate, and the thermostat has to be ENERGY STAR certified and on Dixie Power's approved list at the time you buy it. Buying first and checking later is how people lose it. There is also a rebate tied to 400 amp residential service for all-electric and dual-fuel setups.
Deadlines are short and they are not the same across programmes: the heat pump and 400-amp rebates run on a 60-day-after-install window, the thermostat rebate on 180 days from purchase. Current terms are on dixiepower.com.
Rocky Mountain Power
Rocky Mountain Power runs its residential efficiency incentives for Utah customers under the Wattsmart Homes programme, covering heat pumps and other measures for customers on residential rate schedules. Terms and qualifying equipment change, so confirm current offerings directly at wattsmarthomes.com before you commit to equipment.
We do not administer, process or guarantee any utility rebate, and we quote no figures for them. Confirm eligibility and current amounts with the utility directly.