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Comment by asynchronous13 | Hacker News Reader

I'm an electrical engineer and I've done these calculations for my own home.

The roof area of a 1200 sq ft ranch home is much larger than the surface area of solar panels needed to power the home. (in other words, your map would show pretty much all of north America). But covering all of a roof with solar panels is very expensive.

The biggest problem is that the "typical suburban home" is ridiculously inefficient.

In terms of bang for your buck, investing in efficiency improvements is a much better choice for the average home owner. Don't even consider solar panels until you've reduced energy needs first.

After efficiency upgrades, modern solar panels make a lot of sense financially speaking.

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> Don't even consider solar panels until you've reduced energy needs first.

Absolutely, asynch13! That's what I did. It took over two years, starting with a home energy monitor.

Using a home energy monitor such as [1] or [2], one can get frequent measurements, every six seconds for [1], then identify individual loads by switching them on and off during a period of otherwise steady demand. Other loads silently switch on and off of course;

Then one can start making evaluations and upgrades. Some can be surprising; I was able to reduce my demand by well over 20 KWh / day; details here [3].

After that, a 5KW / 8000+ KWh-per-year grid-tie no-storage solar PV system went in. My utility charges $11 for a month when the PV system produces more than the home consumes during a billig period.

The utility did change out their transformer (to a smaller 25 KW unit feeding 3 other homes) on the power pole in my back yard. But home and location is 40 years old, so I can imagine the old transformer was fully amortized long ago.

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[1] http://currentcost.net [2] http://www.theenergydetective.com/ [3] https://discussions.zoho.com/powersave/topic/how-much-i-ve-b...

They charge you for feeding excess power back into the grid?

Not exactly. Since it was a subsidized system, with 'Net Metering', my utility sets the billing rules. Excluding the finer points, here's the gist of how the billing works:

* My utility (Los Angeles DWP) accumulates a 'dollar banking' credit for the present value of net energy [signed power flow integrated over the two-month interval of my utility's billing period] fed back to the grid when a billing statement period is net-energy-productive (i.e. the PV system made more energy than my home consumed over the statement-period of two months). I pay a $22 'minimum charge' (normalized: $11/mo) for, as I see it, my share of utility equipment amortization and operations I'd otherwise be paying as a consumer. Fair enough: I do draw energy when the sun goes down. It's co-operative.

* In the summer, my 5-ton A/C use exceeds my PV system's production capacity; I become an energy consumer during one or two billing periods. My utility calculates the price for the _net_ energy I use per period, then debits the 'dollar banking' account. If that gets exhausted, then I pay the residual, otherwise my 'dollar banking' balance just goes down.

> Don't even consider solar panels until you've reduced energy needs first.

i suppose its good to watch out for unnecessary power usage (like keeping the lights on all the time), but i will not want to give up any modern luxury to save a bit of power. For example, if its hot, i will turn on the AC, or heater if its cold, take long hot showers/baths etc.

What i want out of a solar panel is so i can spam electrical appliances all i want.

The cheapest watt is the watt you never had to generate.

I've had a solar installer make a report... it would take a little more than half of my roof (the house is a ~1000 sq ft one-story building).

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