Tracking Energy Use
I got a call today from a builder that I completed a HERS rating for last July. The owner of the house is asking to try to find out why their electric bill was so high during this past winter.
This is a 7000+ sq. ft. summer house that supposedly was mostly unoccupied during the winter.
12 kW solar array
3 air handlers using water coils for heat, propane boiler
1 ERV @ 200 watts running 24 hours, supposedly, tied into one duct system
Mostly LED lighting
Above average refrigerator consumption
HERS score of 33
The owners are wondering why the electric bills during the winter are above $600 per month. They said the house was kept at 65 degrees. The builder was asking if I thought the ERV running 24 hours would cause that amount of energy use. I said no. But I am not sure if the ERV is tied into the blower motor which may also run 24 hours a day if it is.
Ekotrope projects the annual energy use at anywhere from $8100 to $8900 per year, not including approximate savings of $2400 with solar, but most of that is for heating, which is propane, but also for blower motor I presume. And as usual with Ekotrope/REMRate, the amount of energy use for cooling seems extremely low.
The builder contacted the solar company and they checked the online portal and said everything looked normal for that time of year, but did say the consumption seemed high.
During their time here during the summer their electric bill goes to over $1000 per month, which includes a pool, and of course cooling.
The builder is asking if I know of a way to track down what may be causing the high energy use.
Any thoughts on how that may be done. I remember discussions on electric panel monitors and such.
Or does $600 per month during the winter for this unoccupied house seem right as a base load?
Thanks in advance for any thoughts.
gg
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Replies
The ERV is using about 144 kWh per month, which I doubt is much over $36 or so per month, but that depends entirely on your electric rate where the home is located. The rest of that is probably a combination of things, but I'd guess the blower motors are a big part. I assume there are also some circulating pumps if there is a hot water heating system in place. That all adds up.
I find that in my own home, electric consumption in the summer and winter is about the same, only a relatively small increase in the summer from cooling loads, the bigger difference is that the heating costs are added in in during the winter heating season (which means natural gas for me).
My best guess here is that you're electric bill is not too far off, and I assume you're in an area with a relatively high per-kWh electricity rate. You could get a "clamp meter" to go circuit by circuit through the panel looking at electricity use on each circuit, but that will only work for things that are actually "on" while you're looking at loads. Fancier energy monitors are probably too expensive to use for a sanity check like this, but you could install such a system on the larger loads (furnace blowers, circulating pumps, pool equipment, air conditioners, etc.) to keep track of things over time if the owners want such a system to give them better visibility into their energy use over time.
Bill
I've liked the Emporia Vue 2 energy monitoring system that I have. It has 16 clamps that you can put onto 16 different circuits. Leave them there for a week or to, and if you don't find the source of your energy drain, move them to 16 different circuits and leave them there for a week or two. You should be able to trace all of your energy usage this way.
Sense energy monitor is on sale right now.
If they're dropping $600-1000/month, spending a one time $270 for the monitor might be worth it for investigation purposes.
I question its fine accuracy of them, as I've never tried it (yet), but maybe it'll point out something glaring.
Jamie