Furnaces are remarkably reliable appliances that seldom break. But they do eventually need to be replaced, and that’s when things can get expensive. For one, the purchase price of a new furnace is often more than double what an existing model runs. Another potential cost burden is that you may need to schedule maintenance appointments more frequently. These things add up over time and can make it difficult to budget for a new furnace. Fortunately, there are several indicators that will alert you when it’s time to replace your old furnace instead of investing more money in repairs. Here are a few things to look out for over the next few years:

Furnaces are typically rated in terms of heating capacity, but also have a cooling capacity as well. You can easily determine how much cooling your furnace can handle by using a cooling-capacity chart found on the manufacturer’s website. These charts will help you plan for the upcoming cooling season so that you can purchase the correct amount of cooling equipment. If your cooling capacity is less than your current cooling needs, it’s time to replace your furnace. If you’re not sure what your cooling needs are, use the table below as a guide:

Even though you might still be under contract for your existing furnace, it’s a good idea to keep tabs on your gas consumption. You can do this by logging your gas usage, or using an energy monitoring system. If you’re using up to 30% more gas than you did with your old furnace, it’s time to replace it. If you’re using more than 50% more gas, you’re almost certainly paying more money than you have to.

Like gas consumption, carbon monoxide levels are another sign that it’s time to replace your furnace. Carbon monoxide is a byproduct of gas combustion and can cause serious health issues. If your carbon monoxide levels are above two parts per million, you’re likely to see elevated levels of carbon monoxide in your home. If your carbon monoxide levels exceed 10 parts per million, you’re likely to experience health issues and should be evacuated from your home immediately.

Humidity is often overlooked, but it can have a significant impact on your home. When humidity levels are too high, they can cause damage to your home’s wood and masonry. In a single-family home, you might be able to live with a slightly higher humidity than you did with your old furnace. But when you’re living in a multi-family home, or when you want to sell your home, you’ll likely have to reduce humidity levels. You can use an indoor humidity meter to make sure that your humidity levels are in an ideal range.

These sensors will alert you when your home is becoming too warm or too cold, and will alert you when your furnace is broken. These sensors can help you save money by reducing your energy usage when your home is not at its ideal temperature. If you have installed any of these sensors, and they’re not triggering when they should be, it’s time to replace your furnace.

It’s important to recognize that there are plenty of signs that will alert you when it’s time to replace your old furnace. It’s best to procrastinate as long as possible, but you should be prepared to replace your furnace at any time.