[RE-wrenches] Electric Water kWh/ person

[jerrysgarage01]

DrakeWe have used 40 to 80 gallon water heaters mainly the Rheem Marathon electric units, we used 15 minutes per person twice a day on the timer, we did use 7 day timers to have different start times on the weekends. We had great success with that as a base line.Jerry


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-------- Original message --------
From: Darryl Thayer <darylsolar1 at gmail.com> 
Date: 3/14/18  4:14 PM  (GMT-10:00) 
To: RE-wrenches <re-wrenches at lists.re-wrenches.org> 
Subject: Re: [RE-wrenches] Electric Water kWh/ person 

Sorry to say nothing, but a few years ago I did a study on off grid and on grid houses and some had electric resistance water heaters and one with a Heat pump water heater.  If I can find the data I will send.  However, it varied a lot most the families were for 2 or 3 people  The variation made it seem like my study was of little value.  except for the family with a heat pump water heater used about 1/4 the electricity of the other.    
On Wed, Mar 14, 2018 at 6:19 PM,  <drake.chamberlin at redwoodalliance.org> wrote:
Hello Wrenches,

Is there a good way to estimate the power that will be consumed for electric water per person per day? We are estimating the amount of power that will be used by an all electric duplex, and the water heater amount seems high. The current model we have claims 3493 kWh/ year per 26 gallon tank will be consumed. With the two units, that would add up to 6986 kWh / year for hot water, pushing the system size to humongous for a 1300 ft sq building. 

Does that seem high? There will be a maximum of 2 people per unit. 

The owner is considering going to 115 V units with a 15 gallon tanks. I think the smaller tank would help, but it would seem that the amount of hot water consumed would be the main issue. 

How can we get a good estimate for a per person energy usage for electric hot water? Any other suggestions are welcome.

Thank you,

Drake




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