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Seattle- Heat Pump/Gas Furnace vs AC/Gas Furnace

12 years ago

Wonderful site!

I live in Seattle and have a 3000 sq foot house with an oil furnace. We are looking into changing the oil (Thermopride 80% efficient) to a gas furnace. The question is should we go with a heat pump or just add a/c to a new gas furnace?

I calculated the amount of oil used in the past year which was about 554 gallons. Using 138,000BTU for oil, this translates to 76,452,000 BTU of heat used in 1 year. My cost for this was $2474 this past year! Yikes!

So I ran some numbers to compare the equivalent BTU energy (76,452,000 BTU) costs for an entire year for a gas furnace vs heat pump/gas furnace:

-gas furnace 95% efficient (1000BTU/Therm)- 764.52 therm x $1.14/therm = $872/0.95 efficiency = $917/year

-gas furnace 95% efficient/ Heat Pump (3.5 ton 13 SEER 8.5 HSPF COP 3.1) assuming heat pump running 70% of time and the rest gas furnace (3413 BTU/KWH)-

Heat Pump- 15680 KWH/3.1 COP= 5058KWH x $.09=$455/year

Gas Furnace- 229 Therm x $1.14= $261/.95 efficiency= $275/year. So the total energy cost for a hybrid system is $730/year.

If my calculations are correct, then the gas furnace/heat pump is really only 20% more efficient than a gas furnace alone. Does this justify the added cost of a heat pump versus just having a gas furnace and central A/C? I figure the added cost of a heat pump over an equivalent a/c is about $1500-2000 more?

The quotes I have received for a gas furnace 95% efficient variable blower with a 13 SEER 3.5 ton heat pump have ranged from $10000 for a Lennox System (XP13 heat pump/ furnace G61V) to $14000 for a Carrier System (Performace 15 heat pump and Performance 93% gas furnace). Is this a good price for the Seattle area? any comments would be greatly appreciated!

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