When your heating oil furnace or boiler are running at peak efficiency, you will save money. Regular furnace maintenance can save you up to 30% on your heating bill. Your furnace requires periodic maintenance to operate up to specifications. Because your furnace can make up about 50% of your energy bill, it is important to keep it clean and tuned. Your annual furnace checkup should be scheduled yearly with a trained technician. The best months to schedule maintenance are between April and August