New Hot Water Heater - Preliminary Results

TGIF  Readers!
(At least for me at the time of my typing..)

I've got some exciting preliminary energy reduction results!  Recall that about a week ago I installed the GE Geospring hot water heater.  Well, I've been watching the days closely and tracking energy usage and wow has the new hot water heater (and combo crawl space dehumidifier) making a difference.  Below are the graphed results:

As you can see above after turning off the HVAC system and before installing the hot water heater, energy consumption was around 20 kwh/d.  If I was to go further historically, you'd see this a lot.  Even during my lowest month (Spring, No HVAC, vacation for a week), I averaged 17.5 kWh/day.

After installing the unit, my average has plummeted to 14.5 kWh/day.  And me and my wife are still at home...no vacations...doing the same things we do every week (laundry, cook, clean the dishes, shower, watch TV, etc).  That's a 6 kWh/day or 29.4% reduction in energy usage.

Note that this average ignores the day we actually installed the unit (9/8) because the unit had to reheat all the water so that's why there's that big bump (when it first turns on, the startup cycle uses the electric elements to get up to temperature fast).  Also, I needed to make sure everything was OK with the desuperheater/piping/preheat tank so I bumped on the A/C for a short period of time.

OK...so what does this all mean? 

Well, 6 kWh/day x 30 days = 180 kWh/month x $0.113/kwh = $20.34/month in savings or $244/year.  I'll take that.  It's not quite the 9.33 kWh/day of energy reduction I had anticipated, however, this is at a hot water temperature of 130F while the former HW heater was set at 120F.  Why so high?  Well, I read in the Geoexchange forums that if the desuperheater/preheat tank increases the HW temperature to above the Geospring set temperature (which it can in the summer), the Geospring will error out and need to be reset.  With summer behind us and the HVAC off, I'll put the temperature back down to 120F.  I should have done this earlier (since I turned off the HVAC even before hooking up the Geospring!), but I was trying to be conservative to start.  

So, here's another thing...even with the Geospring temperature set so high, I'm still seeing significant savings.  Overall, I'm recording energy usage days at all-time lows (10.7 kwh/day!) even though I'm home.   At the current rate, it's looking like I'll only use 534 kWh for this month (17.8 kWh/d).  My all time low is 526 kWh/month (17.5 kWh/d) and that was during the Spring of 2011.  Note that most Springs I'm around 500-600 kWh while during the fall I'm typically around 700 kWh (~24 kWh/d).   

So what's next on the chopping block?  Well, installing the Ecobee thermostats will wrap up my optimization of the heating, cooling, and hot water systems.  I'm not going to do that until temperatures drop and I actually have to use my HVAC system...so that'll be mid- to late-October, probably.

Then after that I'll start looking at my next two biggest energy users...the HTPC and the Fridge.  From my latest Kill-a-watt readings that Fridge uses about 1.9 kWh/day.  That's about 11% of my current daily usage.  At best, a new fridge will knock that down to about 1.2 kWh/day (0.7 kWh/day savings).  I'm not rushing this investment because the ROI is just not there.  However, I'm not fond of my fridge (too small...even for only 2 people!) so that's why its on the chopping block.

My Mythtv HTPC.

Then there's the HTPC.  One average the HTPC (and all its accessories) is using about 1.6 kWh/day.  I'm looking into how to get the HTPC to 'sleep' between recordings and then 'wake up' when I watch TV.  I'll need a new Wireless Router for this ($100), but besides that it's all software and time to get this going.  Once I figure it out, I should be able to reduce average daily power consumption by around 80%. My ROI?  About 2 years due to the cost of the new wireless router.

Combined the fridge and the HTPC could knock off another, roughly, 1.98 kWh/day...or 11% reduction.  That would put me down to about 15.5 kwh/day average daily usage (currently).  That's pretty dang good for a house that uses all electricity (no natural gas).  Getting lower than this will be very tough (stop using the dryer??)

Then there's looking at solar panels...but that's a whole another story...