A different kind of CMU

We've designed a great new backyard and started the excavation. I rented a Bobcat, Takeuchi TB-16 excavator, and 3 yard dump truck for a couple weekends, and Frank did a great job as truck driver and dirt load cleaner. Fifty cubic yards of dirt, three trees, and a brick patio have been removed so far.

I got bids from licensed landscapers for 100 feet of 4.5' retaining wall and miscellanenous other work. Each came in at about $48K, or about $400 per foot of wall. Tanya researched wall costs for elsewhere in the country and found $35 per foot is typical. Welcome to Marin.

So, it's time to learn about DIY retaining wall construction. "Concrete Masonry Unit" is the term used for what I used to call "cinderblock." You pour a sidewalk-like foundation with lots of rebar in it and sticking up from it. Then you stack courses of specially shaped cinderblock and more rebar. The cavities in the wall run top to bottom and get filled with concrete to complete the CMU wall. Don't forget to put a french drain behind the wall, and get a city inspection at every stage or you'll be jackhammering it apart later. No problem.

No PV at this time

Here's why not:

• PV technology is improving rather drastically these days. A system like this might cost a lot less in a few years.
  
• Our actual energy cost is about 12¢ per kWh right now, making this system take practically forever to pay off unless we start consuming lots more energy. A similar argument explains why I don't grow corn.
  
• The vendor/installer is unclear how many roof membrane penetrations it'd take to install the array on our flat roof, but it's a whole lot. This will invite leaks and make future roof replacement much more complicated.
  

40 x 12 of dead south

Tanya and I really want an A/C for our place to make the house bearable on those 10 - 14 days each summer where the temperature goes over 95°F. Turns out a little 3 ton unit bolted on to the existing furnace will do the job, so maybe we'll get one this season!

But really, the expensive thing about A/C is the electricity. So I got to thinking: flat roof, southern exposure, acres of SiO2...sounds like photovoltaics are in order!

I contacted a local PV system installer (this being the Bay Area there are more than a few to choose from) and here's what he said:

I looked at your house on Google, I believe it is the tan roof facing hillside, no pool. If it is you have 40 x12 ft of dead south. Looks like an excellent site!

The economics of Solar work out in a couple of ways. 1) An excellent hedge against inflation. This works on the same principle as home ownership. You stop paying rent and start paying

down your loan to capture the free sunlight. The cost of electricity for a typical 3 kW system is 8.3 cents per kwH when you factor in the cost over the life of the system. You will get at least 428 kwH on a 3 kW system per month, 153,360 kwH over the 30 year lifespan. There are other factors such as tax deductions and the fact that the system adds more value to the home than it costs to put it on the home, iepeople pay more for solar homes when they are on the market.

A system like this cost about $18,832, after all rebates and tax incentives. The state pays about 25 percent($7,822) of the bill and the Federal government gives a bottom line tax credit of $2,000. The $2.50 rebate is almost gone. Do not delay! It will drop to $2.20 very soon.

If you are paying 32 to 38 cents per kwH in tier 4 and 5 you can see that solar really pays off fast and big. There is no end in site to electric rate rip-offs so protect yourself with a solar system.

If you are paying an average of 36 cents on the 428 kwH you would save $155 per month. $1,860 per year, $60,000 over life of system IF rates do not increase further. At the current 10% per year your bill doubles every seven years!

Let me know if you are ready.