Hi,
Have a HVAC in a two bedroom unit just wondering how to work out power usage for it like $/hour
The only way I can think of is measuring everything else lights, power sockets and then deducting from that.
Will check later if there's any specifications on the machine which might help
Thanks
Record your meter before you go to bed. Crank aircon, make sure everything else is off. Record your meter again in the morning. Determine the amount of power used overnight and divide by the number of hours.
If you are concerned about things like the fridge that you can't turn off at night. Repeat with the aircon off, and see how much the rest of your appliances that can't be turned off (or are in standby mode) use.
For some context that might short circuit the whole situation for OP, my ducted system uses about 7.5kW. I think my power cost at peak time is about 36c/kWh.
what is the capacity of your ducted system? 7.5 kw is huge
Got no idea. It was there when I got there.
@Seraphin7: If your aircon is advertised as 7.5kw, that's its capacity, as in how much capacity it has to heat/cool. Its actual power draw will be more like 2.5kw max and vary depending on the load.
@Keplaffintech: I'll need to have a look at any labels on the unit, but per below it uses 7.5kW when operating.
@Seraphin7: must be a big unit then, like +20kw capacity. certainly on the high end for ducted units.
@Keplaffintech: Apparently it is a big unit. Don't know much about AC, this one being my only experience and then only from ~18 months ago.
7.5kw input or 7.5kw output? There's a big difference.
My 20kw unit uses less than 7.5kw input (at max).
That's how much electricity it uses when operating.
@Seraphin7: Must have a big and/or old unit.
Even my 20kw doesn't draw that much and only at the start.. once the room cools down, it doesn't use that much to maintain temp.
@JimB: When I had a bloke out to look at it when we first moved, he mentioned that it was a large unit. The unit is getting on (now sure how old, but likely original spec or close to … so likely 15-odd years).
@Seraphin7: How big is your house?
15 years isn't all that old.. new ones will be more efficient but it's still more cost effective to repair your older one than replace it.
@Seraphin7: Sounds about right, but after it cools down to your set temp, it shouldn't be using 7.5kw unless you have little insulation or you have set it to 18deg.
@JimB: We tend to run it more in bursts than all day … if we've been out all day, we might turn it on for a few hours when we get home to take the edge of things. Temp set at 22deg typically.
Log into your electrical retailers or distributor's website, it will have hourly or half hourly consumption details
Without using the aircond, oven, washing machine or dishwasher, my power consumption is only about 200w per hour total, so essentially nothing. So there's no need to worry about deducting or switching everything off (just don't use your oven, washing machine or dishwasher when testing).
How much it power it consumes or cost per hour will depend on the temp of the room/house before you turn it on, outside temp, and temp that you set it on. Therefore each day may be different.
The hotter the ambient/room temp and/or colder the set temp, the higher the running costs.
I have a 20KW air cond. Unless I have a heat wave, I generally only turn it on in the evenings to cool the house/bedrooms down to say 24.. and then switch it off when I go to bed. I don't have solar yet but not too worried about how much it consumes.
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You can ballpark it by looking at the aircon specs. A ducted system is somewhere around 3-6kw max load. So if your cost per kwh is 30c, that's 90c-180c per hour max. Replace with your numbers.
For a two bedroom unit it's probably around the 4kw mark.
Thanks will check out the specs when I get home. If not I'll see if I can find the electronic meter to conduct tests.
Grab yourself a Powerpal. Run the HVAC for an hour with normal household items also on, turn it off for the next hour with the other items still on. The difference is your answer.
It looks like Powerpal plugs directly into the meter and doesn't have the ability to isolate loads?
The compliance late on the unit should provide electrical load, both sustained and maximum.
Power consumption is roughly 1/4 to 1/5th of cooling capacity.
Eg - my 22kw ducted system draws about 5 kWh flat out, and at 27c a kWh, costs around $1.30/hr to run.
Of course, it’s rare for the compressor to run flat out, most inverter type systems can spin down to about half that amount. I have noticed thats what i tend to use on a sustained basis once setpoint is close or has been reached.
Any solar you have of course offsets this amount, so calculating your sustained AC load can be useful to calculate what solar capacity you should purchase, if that’s something you are interesting in.
Another way you can do this is to count the number of flashes from your meter in 60 seconds, then multiply by 60 and then divide by 1000 to get units consumed in an hour.
Run a clamp over the energized line to get a real time reading or live reading and counter on a single feed. like this
This is what I'd do. Based on the size of his unit, it's likely 3-phase and you'd need to clamp each line. Can those meters be configured for 3-phase?
my new 5Kw splits use about ~700-1000W when they start up, then they ramp down when they achieve the set temp.
The one in my bedroom averages 200W overnight on a hot night - I have clamp meters on every circuit in my house. (iotawatt)
Its a huge change from my 20 year old model that used to CLUNK on and CLUNK off every 5 mins - and draw 2.4Kw when running.
This iotawatt system looks awesome - having granular usage on each circuit would be incredibly helpful and it looks like it supports 3-phase loads too. How are you finding it? So you only need one monitoring device then CT clamps for each active/line?
It is great. I’ve have it about 2-3 years now. It was a bit of a pain to install. Not much room in the average power board and you need to put the clamps on active or neutral on each circuit not both or they cancel out. Which means either in the board or nearby and you have to remove a bit of insulation and separate the conductors.
I put a recessed box in the wall below the switch box to house the iotawat and a power point for it. And all the CTs have long flyleads and plug in there.
And now I have beautiful graphs and data 🤣🤣
I did a fair bit of research on IotaWatt last night and it really does look like a fantastic solution and I'm about to pull the pin on buying it :) Thanks for the great review and bringing this project to my attention!
You can get power monitoring units that clamp to a wire and report power usage including logging it over time. Safety warning: this involves working on wires that could possible be live, and so official advice would be get a professional to install it for you.
I use Efergy units, only because they were on clearance cheap. https://efergy.com/product/engage/?v=06fa567b72d7
Something like this should get you started
Look for the power rating plate on the outdoor unit.
It should say something like input power kW or rated load kW.
Thats how much kWh you use in 1 hour of typical use on a hot day.
The rating plate cites maximum input current or power, which typically occurs during the start up of the compressor and thus isn't a reliable indicator of true energy usage.
That's why i said rated load.
Best way is to google the model number to find detailed data.
You have one of these for your unit? Based.