It makes sense to try to get the most value out of your home's HVAC equipment, including your furnace. The longer you can keep these pricey appliances operating, the more reward you'll reap from your initial investment. Unfortunately, there's a sometimes blurry line between making a sound financial decision and wasting money on old, inefficient equipment.

It makes sense to replace your furnace after an expensive failure, such as a cracked heat exchanger, but sometimes it's better to install new equipment before your old gear fails. If your aging furnace is still crawling along, these three signs might indicate that it's time to schedule a furnace replacement before it fails and leaves you shivering while you wait for a replacement.

1. You're Still Using a Standing Pilot

Standing pilots are essentially the simplest ignition method available for any gas-burning appliance. These small flames burn all the time, even when your furnace isn't in operation. While they're simple to understand, standing pilot igniters are also highly inefficient since they require a continuous fuel supply regardless of whether the thermostat is calling for heat.

Modern furnaces almost exclusively use electric igniters, so any standing pilot furnace still in operation is likely to be extremely old. While these old units may still work, they're often highly inefficient, and parts are always harder to come by for equipment that's decades old. Scheduling a pre-emptive replacement for a standing pilot furnace can save you money, time, and frustration in the long run.

2. You Can't Maintain Temperature

A correctly-sized furnace should maintain your thermostat's setpoint under nearly any conditions. While frigid weather may test your furnace's heating capability, you shouldn't find yourself shivering if your heater is running. A common symptom of a furnace that can't keep up is long cycling, where you'll notice continuous hot air from your vents without ever reaching an acceptable temperature.

You should always start with a thorough tune-up and inspection if you notice these problems. In some cases, your furnace may just need a little TLC. However, a replacement might be your next best step if a technician can't find anything noticeably wrong with your furnace aside from wear and tear due to age.

3. Your Size is Oversized or Undersized

One unusual situation might be if you've recently purchased a home, only to find that the previous owners installed an incorrectly sized system. HVAC systems work best when perfectly matched to your home. A too-large system can cause nearly as many problems as one that's too small, ultimately resulting in reduced efficiency and reliability.

If an HVAC contractor informs you that your system is drastically undersized or oversized, you may want to consider a near-term replacement. Although installing a new furnace isn't urgent in this case, it's something worth doing to reduce your long-term costs and improve the comfort provided by your home's HVAC system.