First of all, heating with oil is very expensive. The heatpumpp version of an ac condensor doesn't cost much more. You should pay the extra money for a heat pump. Then you can heat with these 'air conditioners' also. Heatpumps do great in milder cold weather and especially good with tight homes.

Regarding the price differences. Some contractors are more hungry to work than others. They might not have the name recognition and don't get leads as easy. There are many good independent contractors who are much cheaper than the 'bigger names' in local hvac. I would go for highest efficiency single stage (roughly 15 seer). Its possible 1 system zoned could make both floors comfy or go with 2 systems instead. I hope this helps.

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Thanks for the response.

You bring up another issue - I understand that oil is expensive, but most of the heating season, the house is not occupied - perhaps 30 days between Oct and April. We keep the temp set at 50 degrees when we are not there. My thinking was our climate is not mild - lots of very cold days, and the amount of oil savings for the time a HP could be economically used might not justify the increased complexity and (presumably) lower reliability and longevity of a HP vs. A/C-only system. But I'm open to advice!

Re: higher SEER - the house is well-shaded and I do not expect the A/C system to operate that often, perhaps 5-10 days per year, but we DO want to be comfortable on those days. Initial cost, simplicity, and reliability would seem to tip the scales toward a 13 SEER system. But again, this is just my (uninformed) speculation.

I like the bang for the buck that 15 seer systems give. They are relatively simple since they are single stage but they are quite efficient.

I think a heatpump is probably less expensive even in very cold weather compared to the price of oil. Unless you have expensive electricity. A heatpump should not have much trouble keep a house at 50 when its 20 outside.

What is your total cost per KW with delivery?
What do you spend on oil to maintain 50 degrees?

Heat pumps are very reliable. The scroll compressors put in them are meant to run, and run, and run.

Going from 13 to 15 does not change simplicity or reliability. It just reduces your electrical usage. Usually the increased cost is recouped in a few years of savings. And you said 'resale' which would be a selling advantage being higher efficiency.

Thanks for the information. I've been checking records and doing some calculations.

Over the past 4 years, we have spent an average of about $4.00/day on oil for heat and hot water, with a 27 year-old boiler with coil DWH. Again, this is not a primary residence - occupancy is averaging about 40 days/year, year-round, keeping temp at 50 degrees when not occupied.

If I read the electric bill correctly, we pay 7.9 cents/KHW.

If a heat pump can operate effectively to maintain 50 degrees indoors at, say, 20F degrees outdoors, what could I expect to pay for electricity per day under those conditions with a 1 1/2 ton SEER 13 or SEER 15 HP?

Another factor I need to mention is that the oil boiler and circulator pumps are leaking and will probably be replaced with a new more efficient unit at the same time as the A/C installation.

It is pretty hard to say what your bills will be but in general, a heat pump with those electric rates in your climate should be 1/4 the cost. If I plug in $4 a gallon, 82% furnace, and a COP of 3, then your electric costs would be about $.90 compared to $4.

Getting an average COP of 3 with a new Seer 15 unit in your climate should be easy.

The great thing about getting off oil is that at your electric rates, even backup electric strips are cheaper than oil...In fact, it is almost 1/2 the cost.

Go with the best equipment - most modern, highest efficiency and quietest with a top of the line manufacturer. With the prices you are paying; I ask for references and talk with the owners in person.

The highest most expensive seer and equipment is not always the best option. Most of the times the simpler the better.

Thanks for all the information and opinions on adding A/C to our second home.

Right now, we are leaning toward two 1 1/2 ton Carrier Performance 25HBC3 HPs, with one VS airhandler in the basement and one in the attic. We are keeping our extremely comfortable baseboard heat, but will replace the oil-fired boiler with a New Yorker FR-HGSI unit.

sounds like a good choice. What will this new boiler be fired with? With 2 heatpumps you might not find the need to use it much.