It had been five years since the boiler installation with no complaints.
Every year during fall, I would contact the heating provider for furnace/heater tune-up to ensure that the whole home heating system was in its best condition, equating to stress-free heating throughout the year. Last year, I had the heating maintenance done twice, in spring and fall. The main reason was that I suspected the gas fireplace of leaking, so I needed it to be checked and repaired before the cold season. I also needed the washable filter replaced since I had recently learned that even the washable ones required to be replaced after some washes but luckily not as often as their counterparts. The HVAC repairman who took care of it told me that as much as I took care of the gas furnace, I needed to consider duct cleaning since it had been five years since the last cleaning. The heating corp where we got the heater from had suggested this, but I had forgotten all about it since it was not something to be done every year. During the home services done over the years, the ductwork never crossed my mind. The technician discovered two leaks in the HVAC duct during the cleaning process. The leaks would explain the rise in the energy bill in the past six months. Later that day, I went through all the paperwork we had for when we purchased the heater, and one of the energy-saving help tips was regularly checking for leaks to ensure the unit runs optimally. The leaks he had discovered had caused the system to run more, thus using more energy.