I think we need to be careful with blanket statements though. Sure, a whole lot of oversized equipment is out there but not all. Im in southern maine, right on the NH border and ive been running manual J's for years. Very few come bsck anywhere near that low and ill bet if i dug a few out, the average is closer to 80,000.
And yet
an older 1400' Portland ME area house analyzed on this forum came in at about 30K, with a plan for cost-effectively reducing to the low 20s.
I'd be very surprised if the average home in ME is anywhere
near 80K, (though I could believe 50-60K), and I'm quite sure the average house in CT is on the order of half that number (or lower.)
But nobody lives in the "average house", they live in
their house, which is why
blanket recommendations for outdoor reset control on a boiler with 150K of output is premature and needs to be analyzed further, which is why I brought up the comparatively low heating load of the typical or average CT house. It's very common (too common) to see 3-5x oversizing factors on boiler, and 2-3x oversizing on the radiation, and even on design-day the water temp needed to heat the house can be well below the safe operating temp for on oil boiler. Outdoor reset isn't safer or useful for many (or even most) systems in CT with a boiler that size, where the boiler was likely sized to be able to deliver reasonable domestic hot water performance with an embedded coil.
The EIA doesn't have a handy 2-pager for CT (or ME), but
they have one for MA. The average home in MA is about 2076 square feet, and uses about 110 MMBTU/year for total energy use, 59% of which (or 65 MMBTU) is for space heating. Over about 6500 HDD that 10,000 BTU/HDD, or 417 BTU/degree-hour. With 99% design temps in the 0-10F range that's about 65 heating degrees, or an average heat load of 65F x 417 BTU/degree-hour, for an average load of about 27,105 BTU/hr. That's a ratio of about 13 BTU/hour per square foot of conditioned space. And that's SOURCE FUEL. BTUs. Assuming an average of 80% efficiency (probably way high), you're looking at 10-11BTU/hr per square foot.
Mind you, nearly half of the housing in MA is multi-family, bringing the average load down a bit, but there's no way that the average single-family home (even the average pre-1980 home) is 2x that number. While rules of thumb are a lousy way to design, the rule of thumb for heat load that comes closest for older homes in MA is 15-20 BTU/hr per ft^2, and most of those older homes can be retrofit air-sealed & insulated to something like 12-14 BTU, which is still somewhat higher than the statewide average of 10-ish per foot when multi-families are included.
The average house size in CT is probably smaller then 2000', but say it's 2500'. At 15 BTU/hr per foot that's still only 37-38,000 BTU/hr, and at 20 BTU/hr per foot it's only 50K. Even with the lower design temps for western ME, I sincerely doubt the average house in western Maine has a heat load over 60K.