To envision how solar power can provide enough juice for an entire house, it's necessary to cover a bit of the basics. We've probably all seen the more traditional solar panels by now — flat, glare-inducing, unwieldy looking things that sit on rooftops.
Solar panels capture whatever sunlight is available and convert it to DC power. An inverter converts the DC power to AC power (which is what we use to power electronic devices). For people who want to completely power an entire home with the sun's rays, there are systems available to convert and store extra power in the form of battery energy. This way, the house still can have a source of power at night or in poor weather (though it can't cover the shortfall of a poorly designed or inadequate system).
Solar shingles are also a subtle, streamlined alternative to the older, bigger panels. They are made from the same materials as traditional solar panels, act as traditional roof shingles and look pretty much like a regular roof ... perhaps just a bit shinier. Contrary to popular belief, the newer panels can work even in weak or scattered sunshine conditions.
So why does converting to solar sometimes take a bit of persuasion? Generally, houses in the United States get heat either from gas or from electricity, usually provided by local utility companies. Let's assume that someone gung-ho on going solar wants off the grid entirely — no gas or electricity from the utility companies. The electricity provided by solar power, then, needs to accommodate for heating, air conditioning (which, by far, is one of the biggest drains of power in a house), other parts of the house's infrastructure like lighting and vent fans, all major appliances (refrigerator, stove, washer and dryer) and other electronics like the stereos, televisions and computers. (This list, of course, is by no means comprehensive: How many members of your family need to constantly charge their smartphones or tablets?)
If your house is huge or you're a power hog who leaves the electronics on all day, you'll need a more intense solar setup. It would be nice to assume that those serious about performing this conversion already are pretty conscious of consumption and making an effort to reduce power usage, like using insulated window shades instead of cranking the a/c, or foregoing a dishwasher that heats up and churns for hours. As solar goes more mainstream, though, the eco-conscious early adopters might not be the majority. They'll want a more robust solar system.
The smart consumer calculates electricity use, then assembles a solar panel setup that can meet that demand. If the setup seems like too much, cutting back on consumption might be in order.
Though it's certainly complicated and can be expensive, people with the resources to design and build a solar-powered home from scratch have some advantages. A lot of subtleties come into play when planning a residential solar system for a specific existing house. The actual design of the house is one such factor. How big is the roof's surface (which affects its potential solar surface area)? What direction does the roof face, and what's the degree of its pitch? Are there obstructions that cause partial shade?
Location is also a factor. A house in Scandinavia, with its notoriously short days, won't fare as well as a house near the equator. The average number of sunny days matters too; if it's raining until nightfall, it doesn't particularly matter if nightfall comes late. If you're building your own solar-powered dream house, you'll have more say over some of those variables.
When you're trying to figure out how much power you can produce with your new solar setup, and how much you'll need, it's helpful to look at meteorological data for your area, too. It'll show you how much sunlight you can expect in any given month, based on past averages. You should have copies of your utility bills nearby, which will let you know how much power you consume. You can use all this information to figure out if the system you want will make enough electricity.
General guidelines recommend a setup that generates 1 kilowatt per 1,000 square feet (93 square meters) of house. But don't let your optimism take over — you need to ensure you can produce enough power to get you through the worst times, not the best. You'll want to literally prepare for the proverbial rainy day.