It is common for homeowners to find that the furnace in the home they just purchased is oversized. You'd hope that something like that would be caught during a home inspection, but that doesn't always happen. Unfortunately, oversizing a furnace leads to short cycling, in which the furnace turns on and off in very short cycles because it heats up the home too quickly.
That may sound great if you dislike a cold home, but it leads to premature wear and tear on the furnace and makes it harder to keep your home at a comfortable temperature. Usually, the advice for fixing an oversized heater is to replace it. However, if you don't have a warranty for it, and there are no available contractual conditions that allow you to have the seller pay for the update, replacing the furnace can be an expensive job. If you don't think you can afford this yet, some strict maintenance can be a temporary solution.
Get an Energy Audit and Batten Down the Energy Hatches
First, get an energy audit of your home done and fix any leaks. Look at redoing insulation if you can, get draft excluders for the bottoms of external doors (and these will help keep cool air in during summer, too), make sure ceiling fans and blinds are rotating and rotated appropriately, and so on. The more energy-efficient your home, the less the furnace will have to run when you need heat again.
Follow a Strict Maintenance Schedule
Follow a strict maintenance schedule for your furnace. Change the filters religiously, ensure nothing is blocking the ducts, and have a heating service check the system over for additional issues. This is also a good time to talk to heating services about possible payment plans that might help you replace the furnace at an affordable rate.
Call Your Homeowner's Insurance Company
Sometimes homeowner's insurance covers furnace replacement for specific reasons. Your policy might include miss-sizing, so it's worth it to check. If the policy does not cover replacing the furnace just because it's oversized, then keep having maintenance done on the heater as soon as colder weather arrives to ensure that it functions as best it can until you can afford to replace it.
No homeowner wants to find out that the furnace is the wrong size, but it happens a lot. You've got time before colder weather comes back, so have the furnace cleaned and change the filters in the meantime. For more information, contact a heating service.