After hours of struggling with the absurdity of this credit on a project with a handful of new appliances and equipment - some that run continuously, some that don't, I decided to walk around the house and look at the nameplate stickers of some familiar appliances.
My refrigerator is not energy star (I know, I know) - the sticker has 115 Volts AC at maximum 7.9 Amps. This equals 905.50 Watts.
My Energy Star coffee maker is clearly marked 920 Watts, no high school physics required.
So great, I have 50% Energy Star Appliances - by Maximum Wattage.
But of course that is silly - because the refrigerator cycles on full about 1/3 of the day so that the daily usage is about 7268 Kwh/day.
The coffee maker, on the other hand, is used for 1/2 hour each morning, so its load is only 450 Kwh/day.
So really, only 5% of my total energy load is 'efficient'.
It seems to me, that the intent of the credit is to save energy, and we can't do that if the measure of a coffee maker is equal to the measure of a refrigerator. And the official intent of the credit?
'To achieve increasing levels of energy conservation beyond the prerequisite standard to reduce environmental and economic impacts associated with excessive energy use.'
As I look through all of these comments on everything from ice-makers to panini grills, it seems we are all missing that basic point.
So, is there an alternate method of calculation that would be more appropriate for mixing refrigerators and coffee makers - one that is based on actual usage in kwH and therefore rewards energy performance of the most energy intensive items?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5907 thumbs up
September 21, 2015 - 12:32 pm
I have not seen an alternative compliance path. Using this rated nameplate power is even misleading when calculating energy use. Your calculations are significantly higher than the actual consumption (I think you are calculating Wh, not kWh). A typical refrigerator uses less than 1000 kWh/year.
I am not sure of the full justification for using rated power other than calculating kWh/yr is often not a simple and straight forward calculation. There are variables introduced mostly replaced to operating schedules. Some equipment cycles part or all of its load which would need a schedule. I suppose we could create fixed schedules but often it is not easy to find how much wattage is drawn by the parts of an appliance. For example, a laser printer has a heating element it that cycles plus all of the other parts that can independently use energy.
I think you make a good point, just not sure how to fix it. I am guessing that the EA TAG at USGBC had the same struggle since this metric did not change for LEED v4.
Michele Helou
PrincipalSage Design & Consulting
72 thumbs up
September 23, 2015 - 10:47 am
yes, high school physics was a while ago. it was wh and Max amps times 3 is probably not right for the fridge and the coffee doesn't brew for 30 minutes. But working backwards - say its a typical fridge at 500 kwh/yr against the typical coffee maker at 100 kwh/yr - you get the issue.
My opinion is that the way to fix this problem is to measure appliances and equipment by kwh/yr against the Federal Standard kwh/yr (which obviously includes estimate hours of usage as a default). Kwh/yr is a much easier number to find also. (no reading the nameplates). If someone wants to argue you need more than one pot of coffee and increased (or decreased) usage, they should be able to alter the default with an explanation. Eventually, there could be standard defaults for different occupancy types the way there are for Water Efficiency credits.
What is your opinion, Marcus, if I presented this alternate calculation method on a spreadsheet for my small CI project with 5 new appliances to see if LEED reviewers accepted it?
Marcus Sheffer
LEED Fellow7group / Energy Opportunities
LEEDuser Expert
5907 thumbs up
September 23, 2015 - 11:29 am
What you propose makes perfect sense to me.
Anyone else know why rated wattage is the metric for this credit?
You could certainly give it a try and submit the rated wattage in the final if it is not accepted.
Christopher Schaffner
CEO & FounderThe Green Engineer
LEEDuser Expert
963 thumbs up
September 23, 2015 - 11:40 am
I agree with Marcus. An alternative approach with weighted usage makes sense and would be consistent with other calculations in LEED (WEc2 for example).
My only guess is that the credit authors were trying to keep things simple.
Rubén M. R.
CodirectorCIVITA
106 thumbs up
December 3, 2015 - 2:29 pm
Hi, Michele. I definitely agree with you. Were you able to present this alternative compliance path four your project? Did the reviewers accepted it?