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Question: Will closing about 50% of the hvac vents in a small apartment cause the blower motor for the air handler to use more electricity?

I live in a 700 square foot apartment. During the day I close the air vent in the bedroom then close the bedroom door.

I do the same thing for the restroom. It has got two small hvac vents. I also keep the restroom door closed.

For sure there is more resistance acting against the blower motor due to the lesser surface area of the vent opening space. I just don't know if that would translate into more electricity usage by the blower motor.

My electricity bill this year is on average about 20% higher per month than last year. The higher electricity bill started in March or when I started using my air conditioner unit.

My electricity bill for June, 2016 was $99.17. My electricity bill for June, 2017 was $121.68.

The February electricity bill was actually about 15% lower than the electricity bill for February of last year.

Thank you in advance.

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    \$\begingroup\$ Measure it! Time the pulses on your utility meter in both conditions with everything else turned off. \$\endgroup\$
    – Transistor
    Commented Jul 16, 2017 at 22:11
  • \$\begingroup\$ No, blower motors use less electricity when there is more back pressure. Of course, they blow much less air, also. \$\endgroup\$
    – user57037
    Commented Jul 16, 2017 at 22:13
  • \$\begingroup\$ More significant is that your a/c may struggle to get the cool air out into your apartment and may end up blowing it out cracks in poorly sealed vents due to the added backpressure. The blower takes a fraction of the power to run compared to the rest of the a/c system. You don't want to waste that precious cold air. \$\endgroup\$
    – horta
    Commented Jul 16, 2017 at 22:17
  • \$\begingroup\$ This is really off-topic for this board. Try diy.stackexchange.com. \$\endgroup\$
    – DoxyLover
    Commented Jul 16, 2017 at 23:05
  • \$\begingroup\$ It's warmer in June unless your in the southern hemisphere \$\endgroup\$
    – Voltage Spike ♦
    Commented Jul 17, 2017 at 15:05

1 Answer 1

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A centrifugal blower pushes air. The more air it pushes, the more power the blower consumes and the slower the blower will run. When you close vents, you are creating a back pressure which reduces the blower's ability to push air. Since the amount of air pushed is reduced, so is the power the blower consumes. At the same time, the speed of the blower will rise.

An interesting corollary of this is if a centrifugal blower from an HVAC system is allowed to operate in open air, it will often burn out due to the excessive power dissipated in the motor from moving more air than what it was designed to do.

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