Air source heat pumps don't make sense in areas where winter temps frequently fall below 32 degrees. Once you get below freezing, you will be running the auxillary heat a lot. If you decide to go the air source route, you will want a second stage gas fired auxillary heat. I live in the mid-atlantic region in the mountains and selected GT. That choice was coupled with a blown cellulose insulation package. My other choice was a propane heat/electric AC with a foam insulation package. Both options were roughly the same install cost. Both would have provided similar energy efficiency. At the time we selected, propane was 3.75 a gallon and rising (with no end in sight) so we went with GT. The delta cost for the GT system (above the cost for a HE propane heat and electric AC system) was $15,000 for the heat pumps and loop plumbing (including pumps) plus $17,000 for digging the pit. The pit excavation should not have cost as much as it did but it is a 12 ton system and the hole was gigantic (120' x 48' x 6'). We live on a mountain and hit a bunch of boulders that required special equipment to get out. Rocky soil also required a 1' base of stone dust to cover the loop piping. The total cost for the GT HVAC system including all ducting was $50,000 plus the pit excavation cost of 17K. It is a large investment and I would only recommend it if you plan to live in the house a very long time. My heating bills are great - maybe 300 dollars maximum a month during peak winter for an 8500 square foot home (5900 living and the rest a condiitoned but unfinished basement). Make sure that whatever equipment you choose can be maintained by more than 1 very qualified HVAC company who has many years of GT experience. In my area there is only 1 GT company who has over 20 years of experience but I am stuck with them for maintenance. There have been times when I wanted to fire them but cannot. Local competition is a good thing. Also - if you build a tight home make sure that you consider ventilation and dehumidification in the HVAC design. I wound up adding both a whole house dehumidifier and energy recovery vent after we moved in becuase we had basement moisture issues as well as stale air in the winter. Tight homes are great for energy efficiency but can create health issues too. It is easy to deal with as long as you plan for it. Good luck with the build.

The DOE has worksheets that can help you calculate the relative cost of heating and cooling with different systems using your current energy costs. Of course you need to predict the relative costs over the next decade or two to really tell what is best. How is your crystal ball working? I would like to clear up a couple of common misconceptions. One type of heat does not dry a house in the winter any more than another. Leaky house envelopes dry houses. Heat by flame of some sort might dry a house more because they draw more outside air in if there is not a source of outside combustion air. That would be the only mechanism. There is nothing special about heat pumps in poorly-insulated, leaky homes. No heat or air conditioning source works as well in that situation as well as they do in tighter, well-insulated homes.

southermum, We've learned alot in a short period of time talking to other pool owners and reading this forum. It really depends on how you want to use the heater. For example: Are you getting a Spa? A gas heater will heat up the Spa in 20-30 minutes so you can be spontanuous.... a electric pump takes an hour or two to get the spa hot. However, our PB (and friends) told us the gas heater uses a lot of gas ($$) to heat up the entire pool. Are you planning to swim year round for laps or excercise?? If you are you may want to use the elec. heat pump to heat the pool because the monthly cost to heat the pool daily is much lower than gas. We have Natural Gas lines in our neighborhood and decided to go with the Gas heater becasue of the Spa... to get the usage of the spa I wanted to be able to heat it up quickly and not "plan" ahead to use my spa. We can heat the entire pool for those "special" winter days when we want to swim... Ex.. Company for Christmas and kids want to jump in. I love to swim for excercise and hope that we don't miss having a elec. heat pump to heat year round! However, several people who have spas told me they wish they had put in the Gas heater. OR... we know someone who installed both... gas heater to Quickly warm up the spa.... AND electric heater to keep pool temp at a lap swimming temp ALL YEAR ROUND! btw: We are in Central Florida so maybe all this does not apply as much to you. We just began our construction check out my earlier post. GoodLuck

Just to insert another opinion here. There are a few more things to consider. I think Tiger’s estimate of existing oil boiler efficiency is overly optimistic at 82%. Depending on age, 65% might be more realistic. There’s no info on existing ductwork, was it designed for AC as in ceiling mounted that would not be optimal for heat distribution? What type of radiators are installed, aluminum finned or cast iron? What water temperature does the boiler have to heat water to, 140˚F or 180˚F? That also makes a big impact on efficiency and energy consumption! Average COP for a 3-ton Greenspeed in our region is calculated at 3.8. We’re in Montreal. Let’s for argument’s sake say the weather is comparable to Boston in winter. Greenspeed should be run down to a temperature of at least a low of +5˚F. According to Carrier, balance point in Montreal of a 3-ton Greenspeed in a 3000sq Ft home is calculated at ~+5˚F base on the BIN data for Montreal, 1,866hrs of AC & 6,894hrs of heating. Boston is not worse for heating. I think your electrical rate is sky high, however, the market for oil is very volatile. The price for electricity will likely be stable, oil, who knows. You’re looking at 2-very different systems that might not be easily integrated. If going with Greenspeed, oil might best be left as just a backup system. Where’s your oil tank; I hope not buried in the ground! You would need those backup electric heat strips previously mentioned, perhaps 15kW and staged. You might also have to upgrade your electrical entrance to 200amp. IMPO SR