You wouldn’t wait until it snowed to buy a snowblower or until it rained to buy an umbrella.
It is always wise to try and make purchases when items are not in demand.
I bought my lawnmower in late fall, when it was at a clearance price. It was still a new machine, but it was 35% off the regular price. This same reasoning can be taken into consideration when buying a new HVAC system. If you are looking to replace or purchase a new furnace and it is the middle of November, you are going to pay a premium price because they are in high demand. HVAC dealers are very busy in the winter and summer months. They can charge whatever they like because they know that you will be willing to pay the price. It is better to contact them in milder weather like spring and fall. They are usually not as busy during this time and many have specials going to entice new customers. Your HVAC system in your home is one of the biggest investments that you make. If you are able to take advantage of free installation, rebate offers, and percentages off, why not. Sometimes, you can even purchase last year’s model, even though it is still new, and save half off because they want it out of inventory. We all work very hard for our money and sometimes have to save for years to afford a new system. Make every dollar count and shop around. Also, make sure to purchase at the right time of year whenever possible.