This article explains in detail the PV solar, thermal storage and battery storage and propane generator required to be off the grid in a 2000 ft2, energy-efficient house.
A house south-facing roof, 44 ft x 18 ft = 792 ft2.
About 10% of free-standing houses have such large, flat (no dormers), south-facing roofs. Other roofs are facing in unsuitable directions or are otherwise unsuitable, based on Vermont survey data.
Area of a 250 W PV panel, 64.5 in x 39 in = 17.55 ft2
Maximum installation 250 x 792/17.55 = 11.25 kW, 45 panels in 3 rows of 15; cost about $45,000
Northeast production = 11.25 x 8760 x 0.145 = 14290 kWh/y, or an annual average of 39 kWh/d; this is for a solar-south-facing roof, at the proper fixed angle for maximim annual production, with NEW, CLEAN, unshaded panels.
Less production for deviations from these ideal conditions. In fact, on a national basis, these deviations cause about 15% less PV production in Germany.
Northeast ratio of best summer month/worst winter month generation is about 3.8, but this ratio could be greater, say 6 - 8, if much snow and ice and overcast conditions occur.
Two EVs use 2 x 0.30 kWh/mi x 12000 mi/y = 7200 kWh/y
A standard house uses about 6,000 kWh/y; an energy-efficient house about 3500 - 4000 kWh/y
If no heat pumps, a 2000 ft2, energy efficient house uses about 600 gal fuel oil/y for heating and hot water.
If cold climate, minisplit heat pumps, about 75% (450 gal) of the heating and hot water is with heat pumps (increasing the 3500 - 4000 kWh/y) and the rest with fuel oil (150 gal).