The Maine Department of Energy Resources surveys heating fuel prices every other week in the off season and weekly from September through April, so this is the month the numbers start moving again. The last off-season reading, posted for August 24, 2026, put the statewide cash average for heating oil at $5.15 a gallon, with a statewide high of $5.55 and a low of $4.22. Kerosene averaged $5.97 and propane $3.20.
Run that against the tank in the basement. At $5.15 a gallon, every hundred gallons delivered costs about $515, and the $1.33 spread between the survey’s statewide high and low comes to roughly $133 on that same hundred gallons. If you are closing on a house in Maine or New Hampshire between now and Thanksgiving, the tank comes with the deal, and it is the part of the heating system buyers look at least and inherit most completely.
Tanks fail from the inside, which is why they look fine
Maine DEP counts roughly 400,000 home heating oil tanks in the state and says it responds to an average of 1.5 spills a day from those tanks alone. Corrosion is the leading cause, and DEP is direct about the mechanism: it usually works from the inside out. Water and sediment settle at the bottom and eat the steel from below the oil line. The agency says plainly that you cannot judge internal corrosion by looking at the outside of the tank.
That is the honest limit of any visual inspection, mine included. What I can tell you is age, support, protection, and the condition of the parts. DEP treats 25 years as the design life for a heating oil tank, says most failures happen at or past that mark, and publishes a short questionnaire that walks you through the high-risk criteria. Tank data plates carry a manufacture date, and on an outdoor Granby that plate is often the fastest read of the visit. Once a tank is past twenty years, DEP’s own guidance shifts from testing it to replacing it.
What I actually look at
New Hampshire publishes the cleaner checklist of the two states, worth reading before you write an offer. The NHDES self-inspection sheet for basement and outdoor tanks asks whether the tank carries a UL 80 or UL 142 label, whether it sits on a one-piece concrete pad, whether the legs are secured with floor flanges or feet, and whether it stands at least four inches clear of any surface on all sides. It asks whether the supply line is continuously plastic coated copper with no unions or splices, whether the vent pipe is at least 1.25 inches inside diameter and no smaller than the fill pipe, and whether the sight gauge and vent whistle both work.
That whistle matters more than it sounds. The delivery driver listens for it to stop. A dead whistle is how a routine fill becomes an overfill on the cellar floor.
Outside, I look at where the tank sits relative to the roofline. NHDES asks whether an outdoor tank is on the gable end or otherwise protected from roof ice and snow, and whether the filter is covered. Ice coming off a roof in February can clip an unprotected filter housing, and nobody finds the puddle until the thaw.
Inside, the item I flag hardest is the buried fuel line. If the copper line from the tank to the burner runs through the basement floor without a sleeve, Maine DEP says it must be replaced. Where a replacement line is buried, DEP wants the sleeve continuous and both ends standing two inches above the floor so they stay visible. Rust blooming at the slab where a line disappears is not cosmetic.
What a bad tank costs
NHDES counts more than 100 spills a year from household on-premise-use tanks in New Hampshire and puts cleanup anywhere from $5,000 to several hundred thousand dollars. Maine DEP notes that a spill within 300 feet of your well, 300 feet of a neighbor’s well, or 1,000 feet of a public water supply puts drinking water at risk, and that oil in the soil under a slab can send vapors into the house for years afterward. Both agencies raise the same downstream problem: contamination follows the property at resale.
New Hampshire buyers should know about a paperwork trap. The state’s Petroleum Reimbursement Fund covers required cleanup for eligible tank owners who have no private coverage, but eligibility depends on the tank complying with NFPA 31 and the NHDES best management practices. A tank that fails the checklist above carries a spill risk and possibly an uninsured one.
Help exists, and some of it is free
Maine DEP funds grants through the state’s nine Community Action Agencies for income-eligible homeowners with a high-risk tank, plus a separate equipment program that pays up to $500 toward fuel lines, whistles, gauges, filter protectors, and filters with no income restriction. New Hampshire’s Safetank program reimburses up to $3,300 to upgrade or replace an aboveground tank and up to $2,500 to remove an underground one, and in most cases pays the installer directly. NHDES also recommends looking the system over every three months, and says to look and not touch.
None of this is a reason to walk away from an oil-heated house. Most tanks in northern New England do the job quietly for two decades. Heating season is just a bad time to learn a tank’s age from a puddle. A home inspection gives you the visible condition, the age, the supports, and the parts. An annual service call from a licensed oil burner technician covers the burner and the ultrasonic thickness test that no visual inspection can stand in for. While you are thinking about heat, the chimney and flue deserve the same attention.
We inspect across Maine and New Hampshire, and our inspection FAQ answers what buyers ask most. The Maine and New Hampshire office is at (207) 839-6595.