Your Biggest Energy Pig at Home

Our cars, definitely.
That aside, it used to be a tie between our HVAC and plasma tv. HVAC ran more during certain seasons so that probably had the edge.
We got rid of the plasma tv so now it is definitely the HVAC.

 

Transport to work -- cars and airplane.
Our new home came with more incandescent light bulbs than I care to count but I have switched out the ones I know we use for ~ 75 lumen/watt LED. Since cooking is now NG I expect our electric bill to be modest. Certainly less than 150 kWh a month and perhaps as low as 100 kWh/month.

The refrigerator is our home hog. It is an older unit that consumes close to 2 kWh a day. It stays because the home is a rental, and my calcs say that the cost to replace is better spent buying PV.

 

Not the biggest pig maybe, but they bug me: we've got a pair of PVR's (aka DVR, basically the new fangled version of "cable box") that are always on. They throw off a bit of heat, even when they're "off".

I actually shut one of them down with a power button now, since we're not using it that much, but that means it needs hours to redownload the programming guide every time it's turned back on.

I think the day is coming that we'll cut them loose, what with Netflix, rss, youtube and so on.

 

There was a damming news article the other day about the proliferation of set top boxes and how much power they consume nationally- the article said it would take the power of four very large nuclear plants to run all the STB's in the USA.
That's a pathetic waste of energy just so the cable co's can scramble their content requiring a STB (and of course a rental fee!) for every TV.

 

Our subwoofer was a pig I'm sure. It started going bad, and while looking it over I noticed the metal plate on the back was really warm, bordering on hot. This was when it had been "off", overnight, and supposedly in idle mode, consuming very little power. I got it repaired, and afterwards I've hooked it up via the 110 volt outlet on the back of the amp, that's only powered when the amp is on. It seems to be doing ok with that setup, and of course is cool as a cucumber when it's been off for a few hours.

 

All electric house built in the 20's. Pretty much everything snorts except the A/C cause we don't have that. 300% increase in electric bill because of last winter. And yes the appliances are newer but still...

 

Living 3 blocks up a hill from the Pacific Ocean means when it get warm in the house, we walk over and open a window... Looking at the ocean as I write this,, its foggy. (Sorry to those living inland in the heat).

 

I live far from the Ocean, but when it gets hot I too open a window

 

So now I have a challenge:

• $0.10/kWh - current electric rate
  • 7.4A - Soleus
  • 6.2A - Turbo Air
• SEER - $ ratings
  • (9,000 BTU * 13.5) / $580 :: 209.5 (BTU*SEER / $) Soleus
    
  • (9,000 BTU * 19.0 ) / $1,090 :: 156.9 (BTU*SEER / $) Turbo Air

From a price performance capability, the Soleus unit is a better buy giving more BTU*SEER per capital dollar. But there is an operational cost, an extra 1.2A per BTU. So if we plot the operational slope, we'll get two lines that intersect where the capital and operational costs are equal. Beyond that point, the cheaper to operate unit has the advantage. It is the same problem Prius people run up against comparing the "hybrid cost" versus the fuel costs.

Back of the envelope, I'll pay ~$0.10 extra for every hour of operation of the less efficient unit over the more expensive. So we're looking at:

• ($1,090 - $580) / $0.10 ~= 5,100 hours . . . ~212 days (24 hours)

Now some Prius people are road-warriors and some are 'little old Ladies who only drive on Sundays' . . . The question is what about Huntsville AL:

• May-Sept :: full months with +80F hot days
• Jun-Sept :: full months with +60F cool nights
• 4.5 months (May gets 1/2 month) :: potential full time A/C
• 4.5*30 ~= 135 A/C days per year

After the second year, we start taking home the energy savings of the 19 SEER unit. But this is the most optimistic case. In reality, the A/C units tend to run until about midnight and then cycle until an hour or so after sunrise. So we may be looking at the third year before the saving become real. Then comes the question of how long do they last?

Anyone see an obvious problem in this 'back of the envelope' analysis?

Thanks,
Bob Wilson

 

My arithmetic is coming out different

(BTU/hr) / SEER = Average power in watts, so
The Soleus unit consumes 9000/13.5 = 667 watts,
The Turbo Air consumes 9000/19.0 = 474 watts.

Call the difference 200 watts, then the less efficient unit costs you 2 cents more an hour to run.

 

What are the amps given? At motor startup? Expansion valve and evaporator at outside ambient temperature? Or with the expansion valve and evaporator at desired indoor temperature and system in equilibrium? Maybe you should get both and a couple of Kilawatts and test them side by side?

 

Now we're getting into the good stuff:

• 7.4A * 115V = 851W
• 6.2A * 115V = 713W
• ~138W difference, ~1.4 cents

We're close enough and I agree you've correctly identified the rate. What I had done was:

• 7.4A-6.2A = 1.2A difference
• 1.2A * 115V = 138W (I dropped the decimal point!!!)

This really pushes the break-even point way out . . . longer than the 7 year warranty of the unit.

Some other good news, I found a Pioneer unit with the same specs as the Soleus for $485, nearly $100 less. I have to check the parts list but it gives me the option of ordering two of them, 18000 BTUs.

As zone units, they only have to cover their local area with some bleed into the common spaces. But I only have to cool what is needed and not run a big central air unit for a lot of living spaces that we are not in.

Bob Wilson

 

Air conditioner specs read like the tax code and I'm not totally happy with some of what I read. But I was using the 'steady state amps' rating needed for the electrical circuit.

Right now, I'm thinking run the condensate line over to the external unit and see if it can 'drip' on the condenser coils. The heat of vaporization should significantly improve the efficiency and minimize the condensate puddle. North Alabama is also muggy. With a little valve, it would trivial to measure the electrical load with and without the condensate dripping on the condenser coils.

Bob Wilson

 

That's the ticket.

One other possible consideration: is the less efficient unit noisier / BTU ?

 

I put all the TVs and cable boxes, along with the DVR, on power strips. The main box, TV and DVR are on a power strip with a built-in timer, so it starts the downloads going while we're on our way home. This way, it's ready to go when we need it, but off all the rest of the time.

 

Smart. In my house my wife is the only TV consumer so she makes do with NetFlix. We have a 50" Plasma TV in the not-yet-sold home we just moved away from that we did not bother to bring with us.

As for STB and their ilk -- not in my house.

 

Bob,

As I've mentioned in other posts, nowadays I do not automatically buy the most efficient appliance I am replacing. Sometimes the best dirty_energy/$ reduction happens when I buy a somewhat less efficient appliance and spend the money saved on PV generation. It is just a specific case of opportunity analysis, and the results often surprise me. PV benefits from lasting 25 - 30 years while consumption appliances tend to be 10 -15 year lives.

 

I agree, the total system performance is what counts. What I did not have was a good handle on the quantitative effects of SEER ratings.

Moving away from central and ducting to room-by-room, zonal, has already paid a benefit. Having them sized to be under 1kW gives a lot of flexibility when dealing with power outages. Then being able to get some additional efficiencies, well that is pure fun.

Bob Wilson

 

Maybe the smallest energy pig: my electric toothbrush sits on a charging base. It has a charge status display. I'll unplug it for multiple days, just plug it in when the charge drops.

 

Know what type of batteries are in it? Letting the brush discharge them lower may shorten their life.