Many thousands of years later clever individuals learned to harness it even more exactly.

Hero of Alexandria devised a working steam engine around the turn of the first millennium. Some models used solar energy to heat the water. In 1767, Swiss scientist Horace de Saussure devised the first known modern solar collector. He used glass boxes that later evolved into solar ovens. Edmond Becquerel discovered the photovoltaic effect in 1839. He found that sunlight could generate a current in certain electrolytes. But it was in 1954 that the modern solar power industry really started to take off when scientists at Bell Labs developed the first efficient PV (photovoltaic) cell.

Since then there’s been a neverending array of impressive devices that continued to improve in efficiency while being manufactured at ever lower costs. At some point, the curves will cross and solar power will become a viable technology for even more uses than it sees today.

Indeed, that’s already happening to a degree. Solar powered homes have been a reality for decades. Whether using PV (photovoltaic) modules to generate electricity, or collector systems to heat water or supply warmth, those applications are installed in thousands of homes.

While relative to power generated by large utility companies it remains expensive for some applications, in others it’s actually cheaper.

Millions of phones and lights along highways use small solar panels to power them. Homeowners around the country use solar-powered lawn lamps to illuminate their yards without wires or batteries. Battery chargers, electric fences and many more applications use solar energy as a primary power source.

Water treatment in developing countries commonly makes use of solar devices. That may be as simple as pouring a gallon of water into a jug that sits in the sun for a few hours. Or, it may consist of a solar still that not only kills disease-causing pathogens, but purifies at the same time. Chlorine is boiled off and minerals remain behind as the evaporate flows up and is distilled into containers.

Such methods are relatively cheap and require only simple technology, making them a much more viable method for those who can’t yet afford the high cost of more sophisticated applications. Many in rural areas of the U.S. and other developed countries face similar circumstances.

Whether producing non-polluting electricity or enhancing health, or even just providing a convenient alternative to recreational vehicle users, solar power has many valuable uses. With costs coming down and the price of oil, coal and other energy producing materials continuing to rise, those applications stand a good chance of increasing.

That’s a benefit for all of us.

First, you need to estimate how much electricity you require to run your home. If you plan only to supplement your power needs, that’s fine. Then just calculate the percentage you want to offset.

A glance at your electric bill can make the task easy. Most utility bills will show a chart of month by month usage throughout the year. You can average the total, or use the peak demand. If you plan to go ‘off grid’ – stop using power from the utility company completely – focus on the peak.

Those numbers will allow you to estimate how many and what size PV modules you need. PV is short for photovoltaic, the method almost all solar cells use to convert sunlight into electricity. It’s a matter of simple arithmetic to match the area of your south-facing rooftop section to the number and size of modules needed.

Each module will generate a certain amount of power at a given cost. When connected the right way the modules add up, so finding the total output (and cost) is equally easy. For a modest-sized home, the cost of solar panels is somewhere around $10,000-$16,000 at current prices. But keep in mind when planning the expense that there are tax rebates and other programs that will help you offset the amount invested.

But the modules have to connect to something. The connectors, clamps, wires and other components add to the total. They vary considerably. And don’t forget to add installation costs. Most homeowners don’t have the skill to build the system themselves.

The sun doesn’t shine all day every day. It’s dark at night, obviously. Rain and heavy cloud cover will reduce the amount of insolation, as it’s called. Other uncontrollable factors reduce the amount of sunlight available. So, almost anyone going ‘off grid’ will want a battery storage system. Those not taking the complete plunge can draw power from the local utility company during those times.

If your system generates more than you need at any given time, some utility companies will enter into an agreement to buy any excess you put into their system. That’s usually done technically by running your meter backwards when you’re supplying the utility company. It normally runs forward as you draw power from their system.

Naturally, they’ll insist on inspecting your system before finalizing any agreement. In fact, most municipalities will require that you have your system inspected and approved even if you go entirely off grid. They need to ensure that it’s implemented in a way that’s safe for local lineman. During power outages they have to assume there’s no power running through the lines. Your system has to be installed in a way that guarantees that.

Between panels, batteries, installation costs and other expenses most modest-sized solar panel systems will cost in the neighborhood of $32,000-$50,000. Some less, some more. That cost should be offset against what you would pay for electricity from the power company over the lifetime of the system, usually about 20 years without substantial replacements.

But costs are coming down and efficiency is improving as time goes on, as the price of electricity continues to rise. It may well be worth your while to have a solar powered electrical system for your home.

Many countries around the world have impure water that causes diarrhea, typhus and other medical problems. The same is true of certain areas of the U.S. and other developed countries. Building small devices that can eliminate the problem is cost-effective using current technology. Individuals can even build their own.

Solar disinfection, or SODIS as it’s sometimes known, uses a very simple principle. It’s essentially the same as that used to pasteurize milk. Microorganisms that cause health problems can only function in liquids up to a certain temperature. Beyond that, even when they’re not killed, they are deactivated. Amoeba, bacteria and many other small disease-causing organisms can be rendered harmless by this method.

Implementing the method can be ultra simple. A gallon of water in a plastic jug can be treated in a few hours. Simply place the water in a clear, plastic bottle, preferably on a black background to ensure good absorption, and place it in the sun. On a sunny day the process may take less than three hours if the water is moderately clear to begin with. River water, obtained while hiking for example, can be treated this way.

PET plastic is preferable to PVC plastic for this application. PVC, polyvinyl chloride, type plastics have a slightly bluish cast. They block more UV, which is a more energetic form of light, and hence reduce the effectiveness of this method of water treatment.

There are other methods of solar-powered water treatment, too.

A solar water still can be bought or built for a few hundred dollars or less that will treat considerably more water than jugs. They’re usually made in the form of a rectangular container a few inches deep with a glass panel up the side and a siphon hose. The container is often covered with plastic. Glass blocks much of the UV.

As the sunlight heats the water, the moisture evaporates up and condenses on the relatively cooler glass above. The siphon hose draws off some of the water, which is not only freer of organisms, but contains fewer minerals and other compounds, such as chlorine.

The principle is basically the same as that used in desalination plants around the world.

Many locales have little drinkable water but large amounts of salt water readily available. Transforming the salt water into potable water employs the same evaporation technique, but generally on a much larger scale in desalination plants. Only a small amount of salt water can be consumed before it does damage to the kidneys. That’s one major reason that seawater has killed more than one sailor who found himself in the ocean trying to survive.

Solar radiation can kill pathogens in water and it can provide drinkable water in specialized applications. In short, solar power can generate clean water, just as it can generate pollution-free electricity.

Apart from the obvious fact that the sun provides the energy for plants to grow that feed us, there are more technological uses that go back millennia.

The ancient Greeks knew how to harness steam power, some of it generated by solar radiation. Pre-industrial, they regarded the devices as amusing toys, primarily. But some applications were taken seriously. Archimedes designed and had built a large magnifying-type glass that was used to set enemy ships on fire. The Romans adopted some of this technology, as they did much of Greek science.

Thermometers, heat storage containers and many other devices were created over the centuries that relied on energy from the sun. Over time, those devices became more sophisticated and more diverse.

In 1839 another big leap occurred when Becquerel discovered the photovoltaic effect even though it would take another 100 years for devices based on it to become practical.

When sunlight hits certain materials, it causes the electrons in the atoms to get knocked loose from their associated atoms. Electrons moving within material constitute an electrical current. When that current is connected to a circuit, the power generated by the electrical flow can light bulbs, heat water or power a computer.

But electricity isn’t the only form of solar power.

In the 1920s some public heating systems used large storage tanks to trap solar energy. The heated water was then supplied to homes. Eventually, those systems couldn’t compete economically. Gradually, the cost of gas and electricity decreased to the point that it was below those systems’ operating costs.

Those systems fell into disuse and were eventually forgotten. But the technology existed as a mainstream method, not a crank alternative. It worked and was, for the time, a cost-effective solution.

Now there are hundreds of viable applications of solar power, which in one way or another convert sunlight received at the surface to power devices, heat water and supply other energy needs.

Satellites have used solar panels and associated technology to supply needed power. The systems are expensive, but compared to the total they’re a very small fraction of the cost. Closer to home, the same kind of technology powers phones or lights along some highways.

And it isn’t just esoteric applications that benefit from solar power either.

Solar heating systems are employed in thousands of homes. Though solar powered electrical systems are less common than utility power, they are in wide use in rural areas where people want or need to supplement their supply. Many cabins in the Pacific Northwest are too far from the utility company lines to get electricity that way.

Not all devices or systems are hugely expensive, either. Low-cost solar powered lawn lights are dotting many homes today. Calculators powered by tiny solar panels are so cheap they’re often given away as promotional items by advertisers.

Solar power can’t yet compete with large scale electricity generation by big utility companies. But costs are coming down and the applications are growing. It’s had a long past, but the future of solar power looks bright.

Using directed sunlight to warm water goes back thousands of years. Crude mirrors and lenses were used by the ancient Greeks to warm water. In the 1920s some municipalities had functional solar systems that heated water supplied to homes.

Today, those applications have taken on the shine of high technology.

One common form is the use of collector panels, often mounted on a rooftop. Unlike photovoltaic modules, these arrays don’t use layered silicon wafers to generate electricity. Instead, they are more like large, thin, double-paned windows that contain water often mixed with types of salt. The sunlight heats the water by means of the greenhouse effect and the water moves through a series of channels, tubes and pipes into the home or business.

The greenhouse effect, as most people know by now from discussions of global warming, occurs when light enters a transparent medium, but not all the energy is allowed to escape out again. It happens to a high degree with glass because the material allows certain wavelengths of the light spectrum, such as infrared, to enter more efficiently than it lets the energy back out again. So, there’s a net gain in energy on the inside.

Heated water has direct uses, obviously. Whether it’s showering, washing dishes or other purposes, nothing more has to be done to the water other than simply make it available. That’s typically done by storing the heated water in essentially the same way as with ordinary water heaters.

In the ordinary hot water system the water heater storage unit also heats the water. With a solar-powered water heating system there’s no need to, since the water that enters the tank is usually between 95F-150F (35C-66C). The storage tank acts like a big thermos bottle. It’s double-lined and/or made of well-insulated material so the heat doesn’t dissipate much out the walls of the tank.

The temperature range of such systems is fully adequate for bathing, cleaning clothes and other ordinary applications. The only difficulties are ensuring enough sunlight to generate enough heat, and minimal loss of heat through the panels and pipes.

Costs can run to $50,000 or more, though. And local climate conditions may limit the usefulness of the system. But given the local cost of electricity or gas, a home or business solar water heating system may well pay for itself over 10 years.

Solar energy, in the form of light streaming in through the atmosphere from the sun, is converted to usable power by a now-well understood process. Sunlight strikes a PV (photovoltaic) module that respond by generating a current. That electricity flows into a home or business by the same components (wires, circuit breakers) as are used by the utility company.

Wind-generated electricity works by an entirely different principle, but there are some similarities. Wind turns a propeller on a shaft surrounded by a magnet wrapped by a coil of wire. As the magnet turns near the wire (or the wire turns, it doesn’t matter which), electrons in the wire experience a force. That force moves them along inside the wire and that movement creates an electrical current.

Both methods are simple in principle. The sun and wind are there and cost nothing. But converting those energy sources into usable electricity does have costs, along with some interesting physical limitations and engineering challenges.

There are the materials required to build a wind turbine or PV (photovoltaic) module, of course. Creating them is not free. They have to be transported and installed, something which is also not free. And, unfortunately, they are relatively cost-inefficient in terms of the amount of power produced compared to coal, oil and natural gas.

Though improvements have been made, they simply don’t produce the same amount of power as other sources for the same cost.

For example, roughly 1,000 watts per square meter of solar energy reaches the surface (at the equator). But, latitude, weather and other factors often reduce the amount to between 125-375 W/m2. Add in that the efficiency of a solar-powered PV (photovoltaic) module is generally 10-15% depending on how it’s made, and the available energy is relatively low.

Still, given the ability to cover an area the size of a house roof with panels, even that relatively small amount can generate about 1.35 kWh/m2/day. That’s enough to power an average home if the homeowner is careful about usage.

Wind systems have their own unique problems. They regularly kill birds. They rely on almost continual wind. Otherwise, like solar systems, they have to be connected to storage systems. And, they don’t put out the amount of power demanded by most applications.

But even with all these limitations, solar, wind and other alternative energy technologies can sensibly form part of a total power generation strategy. They’re clean, which makes them highly desirable by a society continually striving to improve the quality of the environment. They don’t require importation of oil, or mining of coal or other materials which meet with environmental and political controversy.

With continued technological improvements to increase efficiency and lower costs, they can contribute to supplying electrical demand. It will be sometime before they can reasonably promise to displace a significant percentage of the supply from other sources. But the future is always where the best ideas lie.

Of the approximately 1,000 watts per square meter of sunlight power falling on the surface of the Earth (at the equator), only a small portion can get converted into usable electricity. Part of that loss is because of internal losses. Of the photons that hit a solar panel, only some will knock loose an electron. Of those, only some will travel down the module and into the device before being recaptured.

The latter effect is an issue called carrier lifetime. The longer the electrons wander around loose, the more likely they are to flow out of the module and down wires to an outlet. Most modules can only achieve in the neighborhood of about 10-15% efficiency. But several companies have raised the efficiency of their devices to as high as 20% by extending that carrier lifetime.

By contrast, solar thermal devices use sunlight-heated salt water panels to generate steam that can be turned into electricity. The efficiency is often as high as 30%. But not only are such devices expenses, they are high risk. The high temperature and pressure of the water can do considerable damage if it escapes.

Apart from efficiency considerations, costs remain relatively high.

Most types of solar panel remain fairly expensive. A 30-watt module costs in the neighborhood of $250, while a 195-watt panel will run almost $1000. In order to install a solar panel power system for a modest home will require panels costing somewhere around $10,000-$16,000. Add batteries and other components and the cost is anywhere from double that to triple or more.

Fortunately, as oil and natural gas prices continue to rise, manufacturers have responded. As the market matures for solar technology, research dollars have been spent to come up with new ways of increasing efficiency and lowering costs. Even with the relatively high price of large application panels, the cost is still much lower than it used to be, accounting for inflation.

The cost of PV (photovoltaic) cells has been falling by about 15% per year for the past 10 years. Given that they can easily last 20 years, they can pay back the initial investment, while providing clean power.

And improvements continue. A major European chip maker, ST Microelectronics, now has prototype solar cells that are expected to be considerably cheaper than today’s panels.

Organic compound solar panels are making their way into certain applications like computer keyboards and monitors. Those flexible plastics allow a computer to be folded up or rolled like a magazine. While still expensive, the costs are coming down as the technology matures. A French-Italian company expects to produce an organic cell soon that it estimates will produce electricity at around 20 cents per watt, compared with about $4-$8 per watt for ordinary solar power.

Water heating by solar power has costs that vary, too.

In the 1920s some municipalities used large storage tanks to solar heat and store hot water that was then supplied to homes. As the price of electricity and oil came down, which were used to heat water, they were no longer cost-effective.

But as things progress, those old ideas are becoming new again. Such methods may well soon be competitive again, if current research bears fruit. With the price of oil and electricity from gas and coal-fired plants continuing on the trend of the past 10 years, it would only take a small improvement for new applications to be economic.

But there are dozens of cost-effective solar-panel applications available today.

Lawn lights are a popular example. They come in the form of stakes about a foot long with lights mounted on the stake. On the top of the light are small solar panels. They don’t generate much power, but not much is needed for them to do the job. They can be quickly placed anywhere since they require no wires. They can last for years without any maintenance since they use no batteries and the bulbs are ultra-long lasting.

Calculators that are purely solar powered have been in use for decades now. But that same technology has recently been expanded to encompass laptops. Though they don’t currently generate enough power to run a standard hard drive or monitor, solar power has been combined with new inventions to make that unnecessary. They use something called organic cells.

A standard solar cell uses layered wafers of silicon doped with phosphorus. But other elements and more complex molecules are also subject to the photoelectric effect. Many organic molecules will shoot off electrons when struck with light. They’re not currently as efficient, but they make up for it by being flexible and super cheap. They can be incorporated into certain inexpensive plastic alloys.

That makes it possible to make an affordable keyboard or monitor that can be folded or rolled-up. With this technology, it’s possible to roll up a computer like a newspaper and tuck it in your pocket. Then, it’s unrolled when you want to use it and powered by the available light.

There are yet many more applications that can be powered by a solar system. One common use is electrical fencing. Whether you need to power a dog retainer system or a cattle barrier, low voltage systems are often used to keep animals in check. A small stun doesn’t harm, but it’s often enough to keep them from wandering outside the perimeter. Many can jump over standard fencing, but electrifying the system discourages the attempt.

Powered boats, like cars, have batteries that start the engine and power small electrical devices when the motor is off. Running lights, speedometer and more. But those batteries need to be recharged after use. In the usual case, the running motor recharges the battery, putting back the power needed to start it.

But, clearly, the fact that battery chargers exist means that method doesn’t always work. However, when you’re out on the water, and in many cases even when you’re near the shore, it’s difficult or impossible to use a standard charger. Electrical outlets aren’t universal in docks and nowhere on the water. A solar-powered charger can come in handy just when you need it most.

That same charger can recharge the battery in your RV just as easily. But beyond that emergency use, a solar-powered system can be useful for an RV in lots of ways.

Many times an RV is stationary, with its motor off. Some have generators to power the RV at those times. But generators are noisy and consume gasoline or diesel, producing foul smelling fumes. Not exactly what you want when you’re outdoors enjoying the fresh air. A solar power system can supply at least part of the energy needed. It can run a radio, power a DVD and/or TV, or a small refrigerator.

Electricity generation isn’t the only possible application either. Water heating is a popular home-oriented application for solar power.

Small parabolic dishes can be used to focus the sun’s energy into a small area. That energy is then transmitted to a water storage system. Not all such systems are solely for inside the house either. The hot water supplied can be used to bathe the dogs outside or provide an alternative to washing the car with cold water.

In fact, any kind of washing chore is usually easier with warm water and water from the hose gets cold quickly. A solar heating system can provide a reservoir of warm water to wash the exterior of the windows, supply a sink in the garage and other uses around the house and garage.

Solar systems today are more efficient and lower cost than ever. They provide freedom from dependence on the utility companies for all your electrical and hot water needs. That makes them a good deal.

But there’s another way of generating electricity, one that’s actually been in use for some time: heating water.

Steam generation plants have been in use for decades. Usually, the water is heated by burning coal, oil or natural gas. The heated water is turned to steam, which drives a turbine. That circular motion can be used to generate electricity.

Michael Faraday, the great 19th century British scientist and inventor, discovered that if a coil of wire is turned near a magnet, electricity is produced. That effect is the basis for countless applications that use a generator to provide power. The same basic principle is at work in turbines, only in this case the turning is provided by steam power.

But the turbine doesn’t ‘care’ what heats the water that turns the blades that produce electricity. And using solar heated water is significantly less pollution producing than other methods, even taking the component manufacturing effects into account.

One such method is that used in ordinary solar water heating systems, which typically use collector panels atop a roof. The water is heated by the greenhouse effect and then passes down a series of channels and pipes into a storage tank.

But there’s a difficulty.

The total sunlight received in a given area at one time is fixed. It will vary depending on cloud cover, dust in the air and other factors. But it can’t be adjusted upwards, since we can’t control the sun’s output. However, by adjusting how that energy is used, we can control the amount of usable energy applied and how.

More efficient collector systems make that possible. One is the parabolic mirror method.

A mirror shaped roughly like a section of a sphere can focus the sun rays to approximately a point or line. Exactly how sharply focused and to what geometry is determined by the quality and shape of the mirror. A circular parabola, like a satellite dish, focuses to a point. A cylindrical parabola focuses to a line. That shape concentrates the energy received into a smaller area. That makes it possible to use the same energy to raise the water temperature much higher than by other methods.

By using parabolic troughs and other shapes, solar heating collectors can raise the water temperature to as much as 428F(220C). Water boils at 212F (100C). That extremely high temperature water creates steam under very high pressure in a contained vessel. The steam is then used to power a turbine to produce electricity.

Since the temperature and pressure are high, the conversion efficiency of the device is correspondingly high. That’s the result of a basic principle of the physics of heat. That makes it possible to create solar electricity generation devices that are as high as 40% efficient. PV (photovoltaic) panels range from roughly 10-15% efficiency.

Of course, such systems may not be for the average homeowner. Yet. But businesses are beginning to experiment with them as the cost of coal, oil and natural gas rises and the price of solar systems comes down. Some day it may well provide a significant percentage of the total energy needs of the average person, who could receive electricity from large solar turbine-based plants.

The amount of sunlight received in different areas varies considerably. Some places like Santa Fe, New Mexico get sunshine an average of 325 days of the year. By contrast, Seattle has only 58 clear days, 82 days that are partly cloudy and 226 days that are cloudy. In the first case, a solar system would provide ample electricity most of the year. In Seattle’s case, the efficiency would be much lower. For those living in Seattle, many more modules would be required to get the needed amount of electricity. That raises the cost.

Costs vary widely, too. Some homes can be covered with panels for as little as $5,000, though the average is closer to $16,000. Larger homes, obviously, require more panels. Usage varies too. If the home remains connected to the utility company grid the cost is lower since some power is still coming from the grid. Having a battery storage system can easily double the cost.

There are factors that can offset those costs. Federal programs provide tax rebates for those who choose to install a solar power system. Either direct payment or lowered property taxes are the usual methods of reimbursement. Some states have similar programs.

Different solar power system vendors provide their own discounts throughout the year. Some have ‘winter sales’, some agree to match or beat any price from another competitor. Like any product, it’s possible to get a good deal, even on quality material.

At the same time, improvements in manufacturing have lowered the cost of producing the equipment while increasing its efficiency. A wide variety of PV (photovoltaic) modules, batteries, charge controllers, inverters and other components are available today. Most work on the same principle as the others, but like any product some businesses do a better job of manufacturing and marketing than others.

On the other side of the ledger, the cost of electricity from utility companies continues to rise in most areas and there appears to be no end in sight. Rising oil prices, continued heavy regulation of utility companies, the unnecessary death of the nuclear power industry and other factors all contributed to high prices that continue to increase.

At some point in balancing all those factors, which is different for people with different circumstances and points of view, it’s worthwhile to implement a solar power system. Once that choice is made, if carried out properly, most are glad they did. Solar power systems are long-lived, easy to maintain, cost-effective and produce or contribute to minimal pollution.

No single answer to the question posed by the title fits all circumstances. Like most things, implementing a solar power system for your home involves trade offs. In the end, only you can decide whether it’s worthwhile.

Whatever the motives that different individuals bring to the decision, they share a common result: safe, clean, low-cost power. And everybody needs that.