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Energy bill has increased drastically after installing Nest thermostats

brookevc
Community Member

We had 3 Nest thermostats installed in our condo this summer and the electric bill has quadrupled.  From the day the Nests were activated, my energy usage has gone from 5 kWh average daily to 20-25 kWh daily.  No one is at the condo and heat is turned down to 50.  After noticing the higher bill, we remotely turned all Nest thermostats to "off". We are still seeing 23 kWh daily usage.  The heating system is older in our condo, so our electrician had to install a heating relay transformer so he could install the Nest.  Any ideas as to what could be causing this?  

2 Recommended AnswerS

CoolingWizard
Platinum Product Expert
Platinum Product Expert

For me to help you best and make sure you’re getting the most accurate information, I need to know more about your baseboard heating system. Most of these operate with a gas or oil fired boiler and a water circulation pump. The control systems that turn it on and off, I’m speaking of the thermostat, are either operating on a low voltage or on line voltage of 120 Volts.  If the old thermostat was indeed working with line voltage of 120 Volts, then yes the nest would not work and that might explain why they installed a new transformer. However a transformer alone would not solve that problem, you would also need to install an electrical contactor that the thermostat would  energize and thus turn on the heat system.

 

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.
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View Recommended Answer in original post

EdwardT
Community Specialist
Community Specialist

Hey folks,

 

@CoolingWizard, thanks for the help!

 

@brookevc, I hope that CoolingWizard's response answered your question. Let us know if you still need assistance and we'd be happy to help.

 

Thanks,

Edward

View Recommended Answer in original post

10 REPLIES 10

CoolingWizard
Platinum Product Expert
Platinum Product Expert

Brookevc,

your HVAC system when turned off uses very little energy. The nest thermostat draws about 600 to 700 Milla watts of power per month. Basically less than 1 kWh per month. If you are saying that when the system is turned off you’re still like consuming 23 kWh power per month, at maximum 3 kW are used by the thermostats so the other 20 kWh has been consumed somewhere else. 

now basically your HVAC system has an internal control board that consumes power to keep the processor running at all times waiting for a call for heat or call for cooling. That system will consume about 600 W of power in a month and if your AC is running your compressor and blower motor will consume about 3000 to 6000 kWh per hour of operation. In your home any wall plugged in transformer for phones your TV your refrigerator all these things are consuming power during the day and night.

If you really want to find out what’s consuming the power, this will be simple. First you will need a amp clamp probe. You will turn off the circuit breaker for all things in your house . Turning them one by one on you will measure the current draw for each circuit. This will allow you to see which circuits are drawing how much power when things are not being used or when things are being used such as lights. 

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.
If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

brookevc
Community Member

We have no AC.  Nothing has changed at the condo except the addition of the Nest thermostat.  The exact hour the Nest was activated, energy consumption rose.  The condo is empty and no one has been there since the Nest was activated. I can ask my electrician to try your solution, but I'm fairly convinced it has something to do with the Nests or the transformers that were installed to make them work.

CoolingWizard
Platinum Product Expert
Platinum Product Expert

Remember, The transformer itself will be stepping down 120 VAC to approximately 24 VAC and supply it to the internal furnace control board. You say the electrician had to add a transformer? Which makes me wonder how did the old thermostat work if there was no transformer supplying power to the R of the old thermostat? And, Did he install a typical 40VA HVAC transformer or did the electrician install a larger transformer?  
Even if we assume the batteries were at a very low charge state in the nest thermostats when installed, the charging circuit takes about 300 to 400 milliamps of current to charge the battery. The point I’m trying to make is there’s absolutely no way a thermostat or even three thermostats are using 23 kWh per day. The amount of heat energy of 7,666 watts per day consumed by each of the  3 nest thermostats would more than likely melt the plastic base. 

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.
If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

brookevc
Community Member

I spoke with my Electric Company and they explained that Nest thermostats are not designed to work with electric baseboard heat.  I think when we activated the Nests, the heat was turned on, and never turned off, even though we set the Nests to away.  From what my EC told me, I need a specific thermostat designed for electric baseboard heaters.  They recommended the brand Mysa.  If this sounds off to you, please let me know.  Thank you so much for your time and advise. 

CoolingWizard
Platinum Product Expert
Platinum Product Expert

For me to help you best and make sure you’re getting the most accurate information, I need to know more about your baseboard heating system. Most of these operate with a gas or oil fired boiler and a water circulation pump. The control systems that turn it on and off, I’m speaking of the thermostat, are either operating on a low voltage or on line voltage of 120 Volts.  If the old thermostat was indeed working with line voltage of 120 Volts, then yes the nest would not work and that might explain why they installed a new transformer. However a transformer alone would not solve that problem, you would also need to install an electrical contactor that the thermostat would  energize and thus turn on the heat system.

 

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.
If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

brookevc
Community Member

I wish I would have hired you for this project...do you work in Colorado?

I am going up to the condo tomorrow and will further investigate what is happening.  I feel that the heat is stuck on and has been running for the past month.  I should know pretty quick if I walk in my unit and it's warm.  Will try the amp clamp process as well.  

CoolingWizard
Platinum Product Expert
Platinum Product Expert

Brookevc,

I live in southern area of California. Let me see if I can help you a bit more though. Look up AC Cooling Wizard in Seeley, California.  Give me a call when you are on-site and I will see if I can walk you through some troubleshooting.  

Ken, The AC Cooling Wizard

 

NestPro, Google Pro, Mechanical Engineer and HVAC service company owner.
If my answer solved your problem, click Recommend this Answer below, and If it helped you, please give a Kudo.

EdwardT
Community Specialist
Community Specialist

Hey folks,

 

@CoolingWizard, thanks for the help!

 

@brookevc, I hope that CoolingWizard's response answered your question. Let us know if you still need assistance and we'd be happy to help.

 

Thanks,

Edward

EdwardT
Community Specialist
Community Specialist

Hi folks,

 

It's me again. I wanted to check back in to see if you have other questions and concerns. Feel free to let me know if you do. 

 

Thanks,

Edward

Jake
Community Specialist
Community Specialist

Hey there,

 

I wanted to check in with you, and let you know that I will be locking the thread in 24 hours.

 

Best regards,

Jake