Wednesday, December 06, 2006

Just how inefficient is my house

Ok, so I was just running the numbers on my electric power usage for the year and DAMN my house is inefficient.

Ok, the average residential power usage in this country, is 9000 kilowatt hours per year. Very efficient new construction averages between 3,000 and 5,000 kwh per year depending on wher ethey are located, what their heat and AC systems are etc... and a maximum efficiency, single person home can be as efficient as 1000-1200kwh per year.

My house was built in 1953; and is essentially uninsulated filled cinderblock (r value is between 5 and 9, but my AC guy estimated about 8). Theres some insulation in the roof and between some of the interior walls, but for the most part I'm just bare concrete here. Even better, I've got single pane windows, and huge air gaps all over the place.

Basically the only way my house could be more inefficient is if it ws made of overlapping sheets of tin bundled together with copper wire.

Anyway, that national average of 9,000kwh per year? Yeah I did that in August, September, and half of October.

In the nine months since we moved to this new house, we've used a grand total of 20,900kwh, with a peak usage of 3700kwh in september, and a minimum usage of 840kwh in March.

April was almsot exactly twice as much usage as March, because it was the end of march when the AC had to go on.

For this amazingly massive use of power I've paid about $2500; with another three months of relatively small ($120 a month or so) bills to go.

As I write that, I can hear my California readers weaping, because they pay something like 3-5 times what I do for power.

Ok, some allowances have to be made; this is Arizona after all, and summer is damn hot. The air conditioning is literally running 24 hours a day, seven days a week here from about June, until about September (and probably 12hr a day for april, may, and october), just to get the house down to between 74 and 78 .

Hell, It's December 6th, and we used our heat for the first time since March, just last week (we've got gas heat and hot water); and we had a sudden warm spell for a couple days here and used the AC for about an hour yesterday (it got up to 79 in the house).

That said though, the fact that my AC alone is taking up to 3,000 kwh a month is disconcerting.

Presuming 840kwh a month as our baseline usage, that puts us in jsut a bit over the national average, at about 10,000kwh per year; with the remaining 13,000-14,000kwh taken up just in air conditioning.

That's insane. That means I'm paying about $1400 a year in electric bills just to cool my house.

Now, I'm on an LTO arrangement here, so I don't own the house yet, but I'm planning on buying it. I've said before, the very first thing I'm doing when I buy is replacing the windows, and insulating the place.

I've only got 9 windows (Three large triple width casements, and 6 small casements), 2 entry doors, and 2 sliding glass doors in the house; it shouldn't be too expensive to replace the windows and doors with insulated models. The size I'm looking at would be about $600 a piece for the three big windows, and less than $200 each for the small ones. Then there's the $800-1200 each for the insulated sliding glass doors (why are they so damn expensive), and about $300 each for the entry doors.

Total on the windows and doors, about $5,000.

Next step, insulating the house.

First I go around plussing the holes, sealing and filling etc... Then I hit the roof. Roof insulation is cheap and relatively easy. I can revent the roof PROPERLY, and attic mat the whole place to r30 for about $1200.

I would guess that the $6000 or so dollars I'd spend on just those two things, would probably cut the cooling portion of my energy bills in half; so saving something like $750 to $1000 a year. Even being pessimistic I'd guess a minimum of $500 a year savings, so the costs would be recouped in as little as 6-7 years, and as many as 10-12 years.

Next step, we need a new oven, cook top and fridge. The ones I've got are from the late 70s to early 80s; and todays models are between 2 and 8 times as efficient. I dont expect a huge energy savings from those, but we need new ones anyway, and esepcially the fridge will make a big difference.

I already use a bunch of compact flourescents where I can, so there's not much to be saved there; and both Mel and I used laptops most of the time, so the desktop is in standby most of the time; and the other computers are all turned off unless we're directly using them.

We do have a little problem of habits as well.

Mel has this tendency to turn on every light in the house (no I'm not exaggerating, she turns on every single light), and she leaves them on all the time. She doesnt even notice. She also leaves the TV on all the time when she leaves the room or goes to bed, the stero, the computer etc...

No matter what I do, I can't seem to break her of this habit. She really just doesnt seem to notice what she's doing. She swears she's going to modify this behavior.

Ok, so then we've got two major problems left: the uninsulated walls, and the 20 year old air conditioner.

The AC unit I've got isn't actually all that bad, but it's too small for the house, and a newer more efficient model, combined with better ductwork (my ducts vent into uninsulated open dropped cieling space), and the better roof insulation should further cut the power usage for cooling a hell of a lot.

The unit I've got, is a Lennox, HS14-411V-6P; which for 1988 was one of the top 3 ton AC units, with an SEER of 15, and a 40,000 BTU per hour cooling rating.

The only problem is that this house as it's currently insulated needs something like a 50,000 btu per hour rating to maintain proper duty cycle; which is a bit over 4 tons. So, my AC unit is working too hard, all the time, and running inefficiently. These days, I can pick up a 4 ton unit, with an SEER of up to about 18, which means more cooling, for less juice used, more cooling overall, and more reliability.

My current 40,000 BTU unit operating at an SEER of 15, operating an average of about 4500 cooling hours a year (yes, that's really how much it's operating; about twice as much as a 4 ton unit in a well insulated house would) puts out about 180,000,000 btu of cooling a year; for an energy usage of about 12,000kwh; which after taxes and fees et all, costs me about $1200 a year.

That jibes with about how much juice I'm using currently... actually I think I'm using maybe 14,000kwh per year on cooling, or about $1400, but that's still pretty close.

With a cooling rating of 50,000 btu/hr, and a SEER of 17.8 (the trane 4 ton XL19i); a new high efficiency unit, should only have to run about 2200 cooling hours (given the new windows, doors, and insulation, maybe less) for about 110,000,000 btus, and about 6200kwh; which would cost me about $600 a year.

The problem is, one of those things aint cheap at about $5,000 for the compressor/condenser unti, and another $3000 for the air handler and assorted hardware; even saving us somewhere around $600-$800 per year.

Now we could go with a less efficient (15 SEER) 4 ton unit, for about $2,000 and still be running for less than half the time of the current 3 ton unit, at the same energy efficiency rating as currently, but with 25% more btus, thus saving about $300-400 a year instead of $600-$800 a year.

I figure between the windows and doors, the roof, new appliances, and new AC unit, we're looking at about $15,000 to $20,000 in costs; with a total of about $1000-$1200 a year in energy savings.

That means recouping the costs in about 15-20 years... Of course I don't plan on being in this house for 15 years... but the AC unit is coming up on 20 years old, the appliances are all about the same age etc... and the windows are original to the house, so they would all need replacing in the time we plan on living here anyway...

The value proposition is definitely there, but it sure does take a lot of cash up front to be energy efficient.