Solar power, easing into the sun without getting burned

Renewable energy and the environment finally took its place at the top of the agenda during this presidential election. It may have even stimulated some readers into checking into renewable energy. However for the rest of you lazy environmentalists, here is a little primer on what you need to know in order to make your home a renewable energy epicenter. Since this is sunny California, let's examine solar power for your home.

The sun is universal thus solar energy can be generated virtually anywhere. Irradiance is the measure of the sun’s power available at the surface of the earth. It peaks at about 1000 watts per square meter. With typical crystalline solar cell efficiencies around 14-16%, that means we can generate about 140-160W per square meter of solar cells placed in full sun. Insolation is a measure of the available energy from the sun. It is expressed in terms of "full sun hours." For example, 4 full sun hours = 4 hours of sunlight at an irradiance level of 1000 watts per square meter. Solar electric panels (PV) create electricity.

In order to size a system for your home, you need to know how much electricity (kilowatt-hours or kWh) you use each month. That information is available on your electric bill. Once you know how much electricity you use, you can look at systems. The important numbers on your appliances are listed as volts, amps or watts. In the United States, everything runs on 120 or 240 volts with the exception of things like electric dryers and large power tools which may use 240 VAC. You also may see  voltage written as 110 or 117 volts but it's just a way of rounding off the number. So here is your equation for calculating each of your major appliance's energy usage:  

Volts x Amps = Watts.

All appliances are required to list one of these three units. If the appliance only lists amps, then you multiply that by 120 volts to get the watts. A kilowatt is 1000 watts. The amount of time you use a specific appliance is the number of hours. Example, a computer that uses 150 watts for one hour  used 150-watt hours. If that computer runs for 1000 hours, its used 150,000-watt hours or 150 kilowatt (kWh). You will also want information about your peak load or peak power consumption. This is listed on your electric bill or can be found by adding up the wattages of every single load.

The number of kWh you use does not depend upon the square footage of your home. While it is difficult to say what an average household uses, in most of North America, count on an average of about 4 peak sun hours per day over the year. (Note: Peak sun is not representative of how many hours the sun shines per day.) Operating the average home (900 kWh/month) completely off the electric utility grid will require about 75 solar panels (150 Watts each) plus batteries, inverters, fuses, wire etc. A complete solar energy system for this much energy consumption will cost between $70,000 and $90,000. If you want to have a system that's grid intertied and doesn't use batteries, the cost is reduced by about a third. Typically, solar electric systems take from 12 to 20 years to pay for themselves based on your location and local utility charges for electricity.

If you use as much electricity as our average home (900 kWh/month) or more, the first step is to reduce your electricity consumption. Take advantage of new, efficient technologies and know how and when you use power. These are some of the most cost effective ways to reduce your electrical use.

Homes which use electric heat can install solar air heating systems in conjunction with their electric heating system to significantly reduce the amount of electricity consumed by their heating systems. Based on location and the cost of electricity, these systems can pay for themselves in as quickly as 3-6 years.

For homes which use electric water heating, installing a solar water heating system in conjunction with the existing hot water tank will greatly reduce your electricity consumption. Like the solar air heating systems, they pay for themselves in 3 to 6 years.

In places like Los Angeles, solar attic fans are a low cost, easy to install way of reducing the amount of air conditioning used. Also, in our dry climate that gets hot in the summer time, use an evaporative cooler, known as a swamp cooler, instead of an air conditioner. These appliances use a fraction of the electricity that an air conditioning unit consumes.

Remember, you don't have to do a complete solar power system all at once. Pull a few circuits off the main circuit breaker panel and run those circuits off solar. Or you can install a utility intertie (also known as grid tie) system that will feed some solar generated power back onto the utility lines turning your meter backwards and off-setting power that you would buy from the utility. This is less expensive than an off-grid system because there are no storage batteries and because its' not necessary to cover your entire load.

Most utilities have what is called "net metering" which means that a solar system installed on your property can be used to generate electricity and turn the utility meter backward. This allows you to offset power that you would buy from the utility. As long as you only generate the amount of power you use on a monthly basis and don’t generate extra to sell back, you fit into the net-metering category. These systems can be set-up to charge batteries for back-up power systems, in addition to turning the utility meter backwards, but it adds some increased cost. Make contact with your utility to see their rules. Many states offer incentive programs for people to buy renewable energy programs to offset the costs of purchasing and installing systems. Check into it and see what solar power systems are feasible for your home. Then see what incentives California has for their installation. Don't get burned on your electricity bills this winter, see how sunny California can lower your energy costs.