Is natural gas available in your area? If it is, you can go from about 65% efficiency to about 96% efficiency. Outdoor reset control is a must have. This will lower the water temperature from the boiler on warmer days when higher temperature is not needed, saving you money and energy. IâÂÂm surprised this was not proposed, itâÂÂs a big energy saver and relatively inexpensive to install. Boiler should have temperature and pressure gauges. Are your baseboards aluminum fin or cast iron? How do you heat your domestic hot water? Even with a series plumbed system it is possible today to modify the radiators to close and bypass the flow when a set point has been reached in that room thus setting up automatic zoning, saving energy, and ensuring higher temperature water further out from the boiler. This would be when a variable speed circulator may be of use and adding efficiency. Automatic air elimination devices should also be added to prevent air lock and associated problems. This would also reduce maintenance and nuisance service calls. The expansion tank should be checked and properly calibrated, assuming there is one. The bottom line is thereâÂÂs a lot that can be done with your system. As the technology has advance by quantum leaps over the past couple of decades you need someone who is passionate about radiant, follows the latest improvements, goes to tradeshows and attends technical seminars. The new radiant technologies are HOT - I LOVE them! SR

Smaller units will require a smaller backup genset to run one at a time if you want to do that. (Inverter units are already very good with gensets, btw.) As others have pointed out, efficiency may be higher with the 1:1 systems. Some mini splits can cool and heat simultaneously transferring heat from one room to another, but these are rarely seen in residential situations because they are more expensive. It may only be available in systems with more indoor units. There is one downside to heat/cool units if you only need cooling. Complexity is increased meaning more things to break. I don't know if that is significant. I had a reversal valve fail under warranty which cost the installer, but not me. Note that if you have oil heat, the heat pumps may be a less expensive way to heat. Two 1:1 systems means another compressor unit sitting outside. If I had all 1:1 systems, I'd have seven compressors sitting on pads :-( You should know that the better mini splits have inverter-controlled compressors and variable speed blowers. This combination increases efficiency and comfort by stabilizing temperature and improving humidity control. Now consider this. A single unit that can throttle back to 30% of 6000 BTU can run at a 2000 BTU minimum. If you have an outdoor unit that can run 12,000 BTU your minimum becomes 4000 BTU. I believe that the smallest multi Mitsubishi compressor unit is 20,000 BTU so in this example, its minimum might be 6,000 BTU so you gain little from variable speed unless you are running both units at the same time. This would be enough to make me go with 1:1 in your situation despite "slight" increased cost and another unit to maintain. In addition to those arguments, if the price is similar, but you are running one compressor at a time most of the time, you get more longevity for the compressors.

jaganreddy you have provided a nice anecdotal story with very few facts. let's fill in the details. 1.your location 2.was a load calc performed for correct sizing and given to you in writing? 3.provide brand,mdl number, and size of both outside condenser and inside air handler for both upstairs and downstairs systems. how large an area for downstairs? 4.what size heat strip for HP system was installed? 5.what mdl thermostat? what is your usual thermostat setting, both AC and heating mode? thermostat is located on inside wall? 6.does your home have good new construction building/insulation qualities? 7.how many returns for upstairs system? 8.when you say "expensive electric bills", what amount and for what time period? how many KWHs burned? 9.have you eliminated the possibilty of another "appliance" malfunctioning? 10.what is the average winter temp for your area/location? 11.is your electric bill reasonable when operating two condensers in AC mode? 12.does your HP run continuously in heating mode? my first thought is that the backup electric heat strip may be operating when it shouldn't. if so, this could be an installation issue. have you called back GC or HVAC sub to discuss your concerns? Post back. This forum does want to help you. TD

"In terms of the Bosch I doubt it would make much difference if you sized it for heating... unless you needed more heat than a 5 ton unit can produce." Name plate capacity of a heat pump refers to cooling mode only. The term "ton" refers to a ton of refrigeration which is 12,000 BTU/hr. Heating capacity is usually referred to in BTU/hr. The heating capacity of a heat pump declines as a function of decreasing temperature, so it can't be labelled without defining the outdoor conditions. Stated otherwise, a 5 ton heat pump does not have the same heating capacity as a 60,000 BTU/hr furnace--the capacity of which is independent of outdoor conditions. "However, the Bosch can deliver heat down to 5F." That statement can be a bit misleading. While a particular heat pump may be able to extract useful heat down to 5F, that doesn't guarantee it will be able to do so at a sufficient rate to meet the required heating demand without supplemental (backup) heating e.g., electric resistance heat strips. When evaluating a heat pump in heating mode, we're interested in determining the balance point--the outdoor temperature at which the heating load of the home and heating capacity of the system are equal. Below that temperature supplemental heating will be required. For most heat pump systems and most homes (excluding uninsulated homes and super-insulated homes) the balance point usually falls in the 30 F to 35 F range. To be clear, that doesn't mean a particular heat pump won't extract useful heat below that temperature---it just means the amount of heat won't be sufficient to meet the total heating load required and backup heat will be needed. I suggest you consult with an HVAC design professional who can calculate the heating and cooling loads for your particular home and your particular climate zone. Those can be used to select the appropriate equipment and to design the duct work if you elect to go with a ducted system. And, for what it's worth, mike_home has been a contributor to this forum for a number of years. In general, his posts suggest that he knows what he doesn't know. That's more than I can say for some "professionals" here on houzz.com