residential solar and wind systems

8/8/2019 Residential Solar and Wind Systems

1/5

Residential Solar and Wind Systems: What

Are the Costs?

Most Texas homeowners considering a solar energy system or residential wind turbine systemwill quickly face sticker shock. Wind turbine systems can run as high as $65,000 installed. Theaverage cost nationally for a professionally installed solar panel system is about $8 to $9 perwatt. A 2 kilowatt (kw) grid-tied system can run to $16,000. A similar 5 kw system can costupwards of $40,000. Deep cycle back-up batteries for both wind and solar can add on 20 to 30percent more. You might be able to save around $2 per watt by doing the work yourself;however, energy efficiency programs may have certification requirements.

Because both residential and commercial demand for wind and solar energy is increasing, thetechnology is improving, there are more manufacturers, and the price is dropping. In the case ofsolar energy, the cost of an average solar panel in 1980 was $21 per watt. Today, the average

cost is about $2.50 per watt (low =$1.42/watt, high=$3.75). In 25 years, thats a cost reduction of90%. Power output capacities have also improved. In 1980, a typical solar panel might put out 22watts. Now, 100 watt panels are common, if not plentiful. Thats a 450% increase in output. Addto this new enhancement through tracking (a motorized mount tracks the sun through the day toimprove efficiency) and concentrating sunlight to extract up to 75% of the suns rays thatincreases efficiency by 1000 times over regular flat panels. Even if incentives arent available inyour area, any solar or wind energy system installed by December 31, 2010 the Federal EnergyEfficiency Tax credit lowers the cost by 30%.

The reason residential renewables are expensive is simple: you are investing in a home-sizedpower plant. Like any large scale power plant, thats a long term investment made over the

course of 15 to 25 years. And, like any long term investment, you should first take a few minutesto consider your needs and goals:

y How much electricity do you use each day?y In a rural setting, will it cost more to bring more to bring poles and wires to your home?y Is your goal to have self-sufficiency while retaining a grid-tie?

Remember home size is irrelevant. The issue is purely how much energy you use because youare going to want a system that can meet your usage needs.

Figuring your usage

There is a big difference in watts and watt-hours. The power (watts) required to run things inyour house is not measured the same way as your utility bills show (watt-hours). A 50 watt lightbulb burns 50 watts of power each time its turned on. So the electricity supply has to be able toprovide that 50 watts of power when the light is turned on. If you have a 30 watt battery, the 50watt bulb wont light all the way and quickly run down the battery. Watt-hours, meanwhile arethe units of measurement of energy used over time. So, a 50 watt light bulb will consume 50watts per hour (or even 50 watts per second if you are measuring in seconds). The important


2/5

thing to remember is that watts and watt-hours are NOT interchangeable in making yourcalculations.

That being said, the way to determine your usage is to review your utility bills. For example,lets say you use an average of 1000 kWh per month. That divides out to 33.33 kWh per day.

The next step is to find out what electrical appliances and devices you are using, how many wattsthey consume, and how long do you use them. To compute kWh of a device or appliance,multiply the watts times the hours it runs during the day. A 500 watt chest freezer running for tenhours will use 2kWh of energy. If you only know the voltage and amps an appliance is using,there are lots of web sites that calculate wattage.

The next thing to look up is the amount of direct sunshine your location receives (insolation). Itis controlled by the angle of the sun, the weather, atmosphere, elevation, and location on theglobe. The further north or south from the equator you go, the fewer hours of insolation. InTexas, insolation amounts vary from 4.5 to 5 hours.

Now we can see how many panels you may need. A very handy tool is the Solar Panel Estimator.Assume your insolation hours equal 4.5. The system efficiency is a product of the efficiencyratings of the current handling hardware: inverter(to convert 12 volts DC to 120 volts AC andsmooth it into a nice, clean 60 hertz cycle), abattery charge controller, and the deep cyclebatteries. Inverters typically run about 95%, charge controllers at 98%, and batteries at 80%. So,if we multiply .95 .98 x.80, we get a system efficiency of .74 or 74%. That means our 100 wattsolar panels actually produce 74 watts. If we compare the output from the Solar Panel Estimator,if our system was 99% efficient, we would only need 74 panels. Since our system is only 74%,we need 99 panels to make 33 kWh/day.

Lighten your load

The easiest thing to do is find ways to cut your electrical use by eliminating inefficient devices.In Texas, the biggest home energy user is air conditioning. A 30 ton central air conditioningsystem with a SEER rating of 13 can use 2.3 kWh. Over ten hours, that adds up to 23 kW 2/3of our electrical load. There are different energy efficient ways of cooling your home. Swampcoolers, for example, work through evaporation though are most efficient in dry environments.Absorption chillers are common alternatives. They heat refrigerant at low pressure until itevaporates, then it loses its heat through condensing back into a fluid at high pressure. The heatsource can be natural gas, propane, kerosene, orsolar heat. Because there is no compressor tosupply pressure, the system uses little energy.

The second biggest user is the electric hot water heater. Heating water in your home accounts for17% of annual energy costs. A 40 gallon heater uses an average of 8 kwh/day. There are severalenergy efficient alternatives: change to a heat on demand system, use natural gas or propane toheat your water, or consider a solar water heating system in addition to your solar panels.

Consider switching to energy efficient alternatives and/or Energy Star rated appliances. Takeinto account any energy-wasting behaviors. Also, think about how well insulated and weather-


3/5

sealed your home is and whether it needs improving. The less energy you can live without meansthe less energy-generating capacity you will need to install.

Lets say that weve installed more efficient appliances and lights, replaced the water heater andair conditioner systems with a solar absorption chilling system that heats water also. That brings

down the usage from 33 kWh/day to 5 kWh/day. Plugging the numbers into the Solar PanelEstimator, we arrive at 16 panels.

Home wind energy has come a long way from when the steel-bladed fan-type windmill wasintroduced to American farms in the 1870s. Small wind turbines that generate electricity areavailable in a range of sizes (nameplate capacity) from roof or chimney-mounted 1 kilowatt(up to $7,000 installed) all the way up to 100 kilowatt turbines mounted on their own tower(about $80,000 installed). Many of those below 1.2 kilowatts are available in kits for the do-it-yourself-homeowner from a home center.

However, while the power output from wind turbines might look appealing, getting the most

watts for the buck is more complicated than solar power. While the sun shines everyday evenwhen its cloudy, the wind is far more fickle. Some parts of the country are also windier thanothers.. Consequently, a consumer needs to do far more research to determine how much windmight really be available for them to harness. Wind speed varies locally at different elevations.While it might seem to be a light breeze at street level, it might be a dead calm at 30 feet up oreven blustery at 100 feet. Hills, river valleys, trees, and buildings also have a big effect on windspeed especially when coupled with urban settings. Local building codes and other rules mustalso be considered.

Lets say you want to add a pole-mounted residential wind turbine to your system. The turbinecost $1800 on-line with free shipping. The 30 foot pole, also purchased on-line with guy wires

and a few bags of concrete cost $500. The total cost comes to $2300. Factor in the FederalEnergy Tax credit and the price drops to $1610.

Lets also say youve done your homework on local average yearly wind speed. The new windturbine will generate 3.4 kWh per day in an average 12 mph wind zone (Class 4). However, thelocal average wind speed is only about 10 mph (Class 2). So we now calculate that with theseconditions will produce an average of 2.8 kWh per day (about the equivalent of 8 solar panels).

By combining wind and solar together, you have an integrated renewable system that becomes areliable source of home electrical energy 24 hours a day, generating an average of 5 kWh/day. Insome parts of Texas, like Austin, where net metering is available, a homeowner can sell theirexcess generated power to the utility company.

Maintenance is minimal for both solar panels and wind turbines. Solar panels directly convertsunlight to electrical energy. To ensure they get the most power, they might periodically need tohave dust and leaves hosed off. Solar panels do wear out over time, losing on average a watt ofgenerating capability over 20 years. Wind turbines usually only have 2 moving parts that areexposed to the weather. Blades are typically bolted onto the hub which is protected by a nose


4/5


5/5

Bounce Energy is a based in Houston (www.bounceenergy.com) . Bounce Energy's goal is provide more

than low Texas Electricity Rates to our customers. With innovative and flexible plans, excellent customer

service, and superior customer rewards, Bounce Energy offers a unique approach to Texas electricity.

residential solar and wind systems

Documents