He's been heating with a pellet stove, which has an even greater distribution problem than a wall-coil mini-split. If that was a satisfactory solution, 1.5 ton single-head mini-split in the same location would probably be good enough. But there are now some pretty good cold-climate ducted mini-splits that are nearly as efficient as the wall blobs that still have decent capacity at -5F to -15F.
A 3-head cold climate multi-split is almost certainly going to be oversized for his loads, taking significant hit in efficiency & comfort. This is a 1400' house built in the mid-1990s. The heat load at -5F or -10F or whatever isn't likely to be more than ~20-22,000 BTU/hr. (If it's more than that it has some serious air leakage or insulation installation problems.
A better oil boiler only saves money relative to heating with oil. It's still way more expensive than heating with a mini-split with 17 cent electricity. If the Peerless is only needed for 3% of the total annual heat, saving 40% from that isn't going to pay for anything.
A 1.5 ton ducted mini-split like the Fujitsu AOU-18RLFCD has an HSPF of about 11, but in the Adirondacks the annual average will likely be more like 9.5, or an average COP of 2.8. At 17 cents/kwh that comes to:
2.8 x 3412 BTU/kwh = 9554 BTU/kwh, or 1,000,000/9554= 105 kwh/MMBTU. At 17 cents that's $17.85/MMBTU.
Even with a perfectly sized oil boiler that uses no electricity and has no standby losses you're never going to get more than 120,000 BTU/ gallon of heat into the heating system, or 1,000,000/120,000= 8.3 gallons/MMBTU. To break even with a ducted mini-split the price of oil has to be less than $17.85/8.3= $2.17/gallon, have zero standby loss, and use no electricity for pumping or operating the boiler. The last time the average price of oil was that cheap in NY state was in February 2005. The
average price since then has been well north of three bucks.
This week's retail price of heating oil in NY is $3.10. That's 50% higher than the break-even price even with an ideal oil boiler, and lower than the recent 5 year or 10 year average price of heating oil. To buy a Firebird or System 2K instead of a ducted mini-split is to bet that the average price of heating oil will be under two bucks for the next couple of decades, or that the average price of electricity is headed toward 30 cents or higher, neither of which seems like a good bet, in fact the converse is more likely.
The price of oil is down from the 5 year average, and may stay down for awhile longer if China's demand growth stagnates and Iran's oil industry gets back into the market. But at current prices the North American shale & oil sand boom is dying fast. Those shale companies who had hedged with insurance policies to guarantee $90/bbl for this years production are cashing them in to stay afloat, but those policies are not being renewed at $90. The current price of oil doesn't pay their expenses. (My in-laws in the oil & gas exploration biz just moved back to Seattle from their Calgary operation after 3-4 years of boom times, and are now trying to sell the project to a company with deeper pockets.) When that oil is no longer on the market, price volatility will resume. Whether that's in 3 years or 5 years, it'll be well within the lifecycle of a boiler or mini-split.
At 30 cents/kwh it's financially rational in NY to un-plug from the grid at current solar & battery pricing. (
In sunnier Australia it's rational at 20 cents/kwh, and the current residential retail rates there are in the 30-35 cent range- the utilities are in an existential struggle to stay solvent.) Prices on solar and wind are still on a fairly steep learning curve, and are already putting downward pressure on wholesale electricity pricing right now, and that pressure will only increase over time.