First, let me say of Photovoltaic Systems that SustainaBuild would recommend that you "first reduce (your energy consumption), then produce". This is true both in terms of cost-effectiveness of increasing your home's energy efficiency and in cost-effectiveness of reducing greenhouse emissions. For most budgets and most homes, there are a number of things that should be done to improve a home's energy efficiency before it would make sense to install Photovoltaic systems, especially in the sun-deprived portions of the PNW. However, the appeal of having free power cannot be denied so let's take a look at where PV currently stands.

The Basics

PV technology converts sunlight directly into electricity. PV modules are measured in terms of Watt-Peaks- the output of electricity under standardized conditions. Although different modules will perform differently under the same conditions, watt-peaks is still a fairly good measure of how powerful a module can be. So, if we have a system with watt-peaks of 3kw, and assuming constant sunlight of 24 hours per day, this would produce about 72kwh per day. We obviously don't have 24 hours of constant sunlight in the Northwest. So how do we know how many hours of sunlight we can expect per day? Insolation. Insolation tells us the amount of solar radiation received at any given area and time. More simply, this can be expressed as sun hours/day. For Seattle/Tacoma, our average is 3.57 sun hours per day, compared to 6.58 for Phoenix. So, in our region, with a 3kw system and about 3.5 hours of sun/day, we can expect to produce on average, 10.71 kwh/day.Given, the fact that the avaerage family uses about 30kwh/day, the current power rates of 8.5 cents/ kwh, and that the cost of a PV system this size would be around $24,000, the payback on this would be well over 30 years. That isn't great right now but things will change.

NanoSolar

Currently, crystalline silicon modules retail for around $8/watt. This is expected to decrease as demand of PV and as the price of electricity goes up. Nanosolar is perhaps the most promosing of low-cost PV systems.

Nanosolar was founded in 2002 with the stated goal of selling PV cells for $1/watt. They are able to produce their panels more cheaply as they simply print the semiconductor of a high-performance solar cell, while only being slightly less efficient than standard PV modules. Nanosolar made its first shipment at the end of 2007. They are currently sold out for the next year, and they are currently not selling to small scale or residential customers. It also isn't clear if they are selling for $1/ watt, although they have not indicated otherwise. When and if they do become available for smaller projects at a $2/ watt installed price, this would give us a much more desirable payback period of around 15 years in the above example. While some companies are focusing on reducing the cost of PV, others are attempting to increase the efficiencies of the panels up to around 50%, which would also help make PV much more feasible. While it remains to be seen when and how low prices will fall, it is very certain that they will go down.

Incentives

Tucked into the recent $700 Billion Bailout were some provisions towards making PV more affordable, including an extension of the 30% tax credit for PV installations, and more importantly the removal of the $2,000 cap on this credit. Also getting in on the incentive action is the State of Washington that will pay homeowners 15 cents/Kwh for energy that is supplied back to the grid, or 54 cents/Kwh if the equipment is manufactured in WA (although I don't believe there currently are any Washington manufacturers). This incentive is currently capped at $2,000.

Where PV Stands

If you have done everything you can to reduce your energy consumption and have room in your budget to add solar energy, then PV might be the right choice. For the rest of us with a limited budget, PV systems may have to wait until they are more feasible. SustainaBuild recommends that if you are going to be making changes to your home, to consider pre-wiring for PV so that when PV becomes more feasible you will be ready to add PV technology without significant changes to your infrastructure. As far as the most cost-effective way of capturing solar energy in the Northwest, consider Evacuated Tube Systems, which pre-heat water effectively, even in sun-challenged locations.