Hey Guys,

At one of my houses the electricity usage is up about 50% over previous years. This is comparing months with the same average outdoor temp and the indoor temp is about the same. The high bills also start with the seasonal a/c usage so I don't think it could be anything else in the house. Seems to me the a/c system must have taken a dive in efficiency this year.

What would explain this? Coolant problem? What should I check? Filter is good.

Thanks!

 

So many things can cause this.

Do you have ducts in attic or crawlspace. Maybe something broke and duct is leaking.

 

There is nothing in the attic. I believe air flow to the vents is as good as it ever was. Nothing with the system has been changed.

I haven't opened up the unit to check if the condenser needs cleaning, but if that were that case it would freeze over, as has happened in the past.

The compressor is somewhat old. Is sudden decreased efficiency an indication some part has gone bad?

 

A location would be helpful in this discussion.

In NJ...... our cooling demand was way up this year. That would provide for an increase on the electric bill.

 

I mentioned in my original post that the average monthly temp between months of comparison was the same. Meaning I'm using a lot more kwh this summer for roughly the same cooling load. The bills are much higher now that anytime in the past 5 years, and are much higher in this house than in my other nearby houses. I'm in central Illinois though if you still think it matters.

It is clear to me that something is wrong.

 

You first need to have the air conditioning system serviced to ensure it is operating properly.

Even in our generally cold climate demand is up considerably.
Check with your utility and they should have the statistics for degree days in your area.
The will have people payed to help you with these questions.

 

First, look to see if your electricity rate has changed. Many of them have increased in the past year.

First you said "one of my houses". Is this in a rental property or do you live there?

 

Quick questions?

Q1 What ws the humidity like? If it's 90 degrees and 90% humidity, versus 90 degrees and 60% humidity, you'll see a HUGE difference.

Q2 If it's a rental, is it a different tenant, same tenant with new child or new room mate?


Q3 Is it a "first time living on their own" tenant?
Because you LITERALLY cannot make things "fool proof"...

“Never underestimate stupid people, They will drag you down to their level and then beat you based on experience.”
—Mark Twain

"Your clothes dryer is broken"
Tenants complain that they have to run the clothes dryer 10 times to get their clothes don't dry, Problem was they didn't know they had to clean out the lint filter because their mother had always done their laundry.

"Your A/C isn't working #1"
Tenant, opens all the windows on a cool summer night for cross ventilation. They leave three windows open. A week later they complain that the central air isn't cooling the apartment down.

"Your A/C isn't working #2"
One cool spring night, different tenant turn the electric baseboard heater all the way up. Then forgot about it. Next day they noticed the room is too warm, and set the window A/C unit blasting at 68 degrees. A/C was sitting directly above a heater that was set for 78 degrees (for 2 weeks) AND THEY NEVER NOTICED.

"Your heater isn't working"
Finally, another tenant complains in February that the heat pump/HVAC isn't working, the downstairs rooms are cold and the landlord needs to do something about it. Turns out they had turned off the central air in the summer, put in window air conditioners upstairs and downstair during the summer, then left the window AC units in the windows. It's February, its 10 degrees outside, and frigid air is pouring into the house through the ground floor window A/C unit, warm air is pouring out through the upstairs window A/C unit. They never noticed; even though the downstairs drapes are gently flapping from cold air flowing in, and the upstairs drapes are sucked up against the face of the window A/C unit.

 

Average temperature and degree days are two different measurements.
Degree days takes humidity into account and could make a big difference in heating/cooling costs.
There should be someone at your utility you can talk to who works with these numbers for a living.
Unless of course you are the very first person to question power bills.

 

I do appreciate the replies guys but you're all kind of treating me like I'm dumb. I have multiple properties all within a one block area and I track the utilities. I have wifi thermostats in the houses so I can monitor the set temp constantly, remotely. I do daily walk-arounds to make sure windows aren't open during heating/cooling seasons. I already mentioned that electricity consumption in this house went way up this summer whereas the other houses did not, and the set temp within the houses hasn't changed much. So pretty much all of the gotchas you guys are listing for me have already been controlled for.

The only thing I can't say for certain is that the excess consumption is coming from the a/c unit. However I can say that it is proportional to the use of the a/c (my utility company gives me daily usage data). So either the a/c is running at a much lower efficiency this summer than it was last summer, or there is an electric space heater somewhere in the house battling the a/c. I've been through the house several times this summer and I would have noticed a heater.

In the highest month I figured the house used 620kwh more than it should have. That equates to a constant 866W load 24/7 for the entire month. That's a lot.

 

Not at all, "when you see horse shoes, think horses, not unicorns."
Those are the most common issues, so people are going through the "common issues checklist".


Ah, adding that info helps narrow things down.
A/C unit probably has a freon leak.

 

A thermometer might help you trace this.

I would expect an 18 degree drop in temperature across the indoor coil.

How long has it been since the outdoor unit was thoroughly rinsed?

Is the 7/8” copper suction line 55 degrees?

Is the 3/8” liquid line less than 9 degrees above outdoor temperature?

 

18 degree air temp drop from incoming to outgoing air while the unit is running? I should be able to test that pretty easily with a couple little wifi thermostats.

Outdoor unit probably hasn't been hosed down in a few years, but it stays pretty clean. Just checked it the other day. It does get rained on regularly...

I can try measuring the line temps. At the compressor outside?

 

Rain isn’t good enough. A condenser can still get dirty enough to die with only rain cleaning it.

The coil should be rinsed until the water comes out clean on the opposite side. The water pressure should be high enough to go through but low enough not to bend the fins.