Dryer energy usage comparison
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By Joe Rice
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Inputs are in yellow.
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Source for some of these numbers:
michaelbluejay.com/electricity/laundry-sources.html
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General Inputs
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Cost of electricity$0.15per kWh
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Cost of gas$1.40per therm
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COP of central heating system (mini-split)3.0
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Energy loss to venting
Traditional electric (vented)
Heat-pump dryer
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InputsInputs
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dryer exhaust rate (cfm)150cfmenergy required to dry a load3.30kWhEnergy usage relative to traditional electric50%
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indoor temp (C)20°Cenergy required to heat makeup air0.43kWhenergy required to dry a load1.65kWh
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outdoor temp (C)0°C% energy that stays inside house5%% energy that stays inside house100%
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time required to dry a load (hr)0.75hrenergy that stays inside house0.165kWhenergy that stays inside house1.65kWh
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energy saved/used by mini-split0.055kWhenergy saved/used by mini-split0.55kWh
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Constantstotal cost per load$0.55total cost per load$0.17
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specific heat of air1005J/kg°C
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density of air1.205(kg/m³)
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ft³ per m³35.31
Traditional gas (vented)
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Convert exhaust rate from cfm to kg/hr
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dryer exhaust rate4.25m³/mingas energy required to dry a load0.22therms
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dryer exhaust rate255m³/hrelec. energy required to dry a load0.21kWh
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dryer exhaust rate307kg/hrenergy required to heat makeup air0.43kWh
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% energy that stays inside house5%
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mass of air exhausted per load230kgenergy that stays inside house0.32kWh
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mass of makeup air per load230kgenergy saved/used by mini-split0.11kWh
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energy that must be added to makeup
air to bring it to indoor temp
1.29kWhtotal cost per load$0.39
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energy required by mini-split to heat
makeup air
0.43kWh
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http://michaelbluejay.com/electricity/laundry-sources.html
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