Estimate annual #2 heating-oil gallons from square footage, climate (heating degree days), and water-heating load.
NOAA / weather.gov publishes climate-normal HDD for most US cities. New England is typically 5,500–7,500.
A typical oil-fired water heater uses ~120–180 gal/year for a household of four. Set to 0 if hot water runs on a different fuel.
estimated annual gallons
711 gal
Annual heating-oil = heating load + hot-water load.
Heating uses the standard residential heuristic:
annual heating BTU ≈ sqft × HDD × insulation factor
Then converted to gallons via 138,500 BTU per gallon of #2 fuel oil and a seasonal burner AFUE of 85%.
Heuristic only — for an exact number, use a Manual J residential load calculation. Oil furnaces and boilers retrofitted with modern flame-retention burners can hit AFUE ratings closer to 88–90%; older units run noticeably lower.
Take this estimate to a real local dealer — enter your ZIP to see who delivers in your area.