What does the One Hour mean in your company name?

The 'One Hour' in our company name indicates our guarantee to be at your home in the predetermined window quoted when you set your appointment. If we do not show up within that window, your service call fee is waived. 1. Express Appointment: This is an appointment that is scheduled during a specified one-hour time slot. You are promised that a technician will arrive at your home within this one-hour time window. You will also receive a call when the technician is en route to your home. 2. Reserved Appointment: This is an appointment that is scheduled during a specified, two-hour time slot. You are promised that a technician will arrive at your home within this two-hour time window. You will also receive a call when the technician is en route to your home. 3. Standard Appointment: This is an appointment that is scheduled during a specified four-hour time slot. You are promised that a technician will arrive at your home within this four-hour time window. You will also receive a call when the technician is en route to your home. 4. Stand-By Appointment: This appointment is for overflow situations. This appointment will not have a specified time. You will receive a call when the technician is en route to your home. 5. Emergency Appointment: This appointment is for an unspecified time after normal business hours Monday – Saturday and all day on Sundays/Holidays. Calls are dispatched in the same order they are received. You will also receive a call when the technician is en route to your home.

Do you service emergencies after-hours?

Yes, we offer emergency services 24-hours a day, year-round.

How much will my service cost?

The size and complexity of your HVAC issue will determine the cost. Because our trained, licensed HVAC technicians must diagnose the issue before we are able to quote you an accurate cost, we require an appointment to be set to complete a diagnostic on your system. Once the diagnostic is complete, your One Hour(R) technician will walk you through all costs using our Straightforward Pricing(R) Guide so there are never any surprise fees.

How often should I service my HVAC system?

It's ideal to service your cooling system each spring and your heating system each fall to ensure you find small issues before they become big problems.

How often do I need to change my HVAC filter?

Your filter should be changed every one to three months, depending on conditions in your home and your region's climate.

Do you offer purchase financing?

We work built relationships with several lenders to ensure our customers are able to restore comfort in their homes. Ask your technician about your financing options.

What are the advantages of a smart Thermostat?

Smart thermostats learn a household's patterns and adjust heating and cooling according to when a home is occupied, give homeowners the ability to control the thermostat remotely, and enable homeowners to reduce their energy use, saving you money.

HVAC means Heating, Ventilation, and Air Conditioning. HVAC systems refer to air conditioners, furnaces, and any unit that cools indoor spaces during the summer and warm them in the winter. In general, an HVAC system takes in air, heats or cools that air, and blows it into a room or any indoor space. While many homes have separate air conditioning and heating units, others have a heat pump that cools and heats the house. Not only do HVAC systems maintain desired temperatures, but they also improve indoor air quality and regulate humidity levels. But most importantly, these units provide comfort all year round.

What is a SEER Rating?

The SEER (seasonal energy efficiency ratio) is a measure of the efficiency of your heating and cooling system.The higher the SEER rating, the more efficiently a unit operates. The SEER rating of any given unit can range anywhere from 13 to 21.

Bringing Comfort Home

With Expert AC Services

One Hour Air Conditioning & Heating® of Gaithersburg

4.8

(210 reviews)

Heating & Air Conditioning

Services By One Hour

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Two One Hour Heating & Air Conditioning technicians standing confidently in front of a service van.

HVAC Repair, Installation & Maintenance

Heating, AC & Furnace Repairs in Gaithersburg, MD

When homeowners want a reliable heating or air conditioning system that they don’t have to think about, they call One Hour Heating & Air Conditioning. We are the premier HVAC service provider in the United States for a simple reason: we actually care about your comfort.

At One Hour, we respect you, we respect your time, and, most importantly, we respect the trust that you put in us to keep your home comfortable. It’s why we back all of our work with a 100% customer satisfaction guarantee for two years, and it’s why we’re always on time—guaranteed.

We Have a Reputation

For Being Punctual, Friendly and Knowledgable

4.8

(210 reviews)

Xiaofeng Hua

05-07-2025

“Gilmer Roras has done a good maintenance job and friendly. He took time to explain what needed to be done and why. I'm satisfied.”

Patti Connell

05-05-2025

“Very helpful No attitude Gave simple explanations”

Jim Kinkead

04-30-2025

“Rojas did a nice job.”

Brian Paulus

04-25-2025

“Mr Roja excellent job”

Ken M

04-22-2025

“Mr Rojas was a great technician. Very detailed in explaining and patient. 4 stars only because I wish he would have cleaned up after himself (dust) and replaced the tape around our system better as there is air not seeping through and wasn’t before he removed it .”

Edward Burman

04-17-2025

“The technician was very professional and polite he took the time to explain everything he was doing and explained the recommendations”

Nicco Evans

04-16-2025

“Technician explained the steps with A/C diagnostic check in a thorough manner. Very pleasant disposition”

Debbie Vanegas

04-16-2025

“Gilmer always does a great job and is very professional. He lets us know what needs attention in our system and tells us about what needs to be done to correct any problems.”

Patrick Levermore

04-15-2025

“He was very professional and did a comprehensive check on the system.”

FrDennis Hewitt

04-10-2025

“Gilmer Rojas is very efficient and explains what he is doing. He said he likes for his customers to know what they pay for and to be satisfied that all is done. He has serviced our unit before and I was glad to see him again.”

Special Offers

Mention these discounts at time of service

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$150

HVAC Inspection and Plumbing Walk Inspection

Coupon must be presented at time of purchase. Cannot be combined with any other offers or discounts. Management reserves the right to modify offers at any given time. Some restrictions may apply.

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HVAC Services You Can Count On

Our customers love what we do because we treat them like the neighbors they are to us. While we carry the One Hour name, we’re an independently owned and operated business with a personal investment in the local community. We back our work with a 100% satisfaction guarantee, provide StraightForward® pricing guides for your benefit, and will pay you back for being even one minute late to an appointment.

Here For You

When You Need Us Most!

Yellow One Hour Heating & Air Conditioning service van with company branding and slogan.

'Round the Clock Availability

No matter the hour, you can trust One Hour to be there to help you when you get hit with the unexpected.
100% Satisfaction Guarantee

We guarantee our materials, labor, and craftsmanship for up to two years from the date of your service.
StraightForward Pricing® Guide

Before we start any work, we discuss your available options so you know exactly what you are getting and how much it will cost. No hidden fees!
Always On Time…Or You Don’t Pay A Dime!®

We understand your time is valuable, so we promise to arrive at your home within the predetermined time window that you select, or your service call is free.