Residential Solar: Which is Best – Ownership or Community Solar?

Solar Farm in Florida

Residential Solar: Ownership or Community Solar

Which is best for you? It really depends on you, your house and your utility. Consider the factors involved in placing a system on your home:

1. Is there room on the roof or ground for the PV array? The average 2000ft² home uses about 60kWh to 80kWh per day. To offset half of that energy a PV array would need to be 8kW to 10kW, and it would occupy an area of 600ft² to 800ft² on the ground, or it would require a roof area of 800ft² to 1000ft² due to required margins and offsets.

2. Will the PV array be a visual detriment to the home? It is possible to have the array visible and attractive with proper selection of materials, but a Homeowners’ Association could be a problem if the array is visible from the street.

3. Will it be financially beneficial? The matter of cost and return on investment (ROI). The federal tax credit provides a 30% reduction on total system cost. If you cannot take this credit, the value is diminished. If you live in a location where other incentives are in place, be sure that you qualify for those incentives.

4. The last factor is your personal reasons for owning a system. Seeing the array on your property, and knowing you’re saving energy and money on your energy bill is an important factor. Backup power is also an important motivator for owning a system, but if power is rarely lost in your area, a fuel generator may be a better option.

Consider these factors that would make community solar a good option:

The alternative to owning a system outright may be Community Solar programs. These programs are not available in all locations but their availability is growing quickly. Community solar farms are usually owned by the utility company. The customer can buy power from this farm through a program offered by the utility.

1. If locating an array on your home or property is a problem due to space or curb appeal restrictions, this may be a good alternative. These systems are huge and usually located within a few miles from your home. If it is a true community solar farm, there will be an area where you and your family can visit to learn about its function and performance.

2. The performance of the PV system will be maximized regarding the solar resource and the financial return on investment by the utility. This will provide the lowest cost for solar electric generation passed on to the utility customer.

The future of residential solar will be a mix of individually owned PV systems with energy storage, and community solar farms. Both will enhance the viability of the grid and reduce costs of electricity during the lifespan of the PV system. You should be able to pick the one that best fits your lifestyle and goals.

Kelly Provence CEO


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Converting Solar to Usable Energy

Photonic energy is a wave particle that travels at a speed of approximately 300,000 kilometers per second (186,000 miles per second). Almost everything reacts to this energy when contacted by it. The most common reaction is conversion to heat. Plants convert sunlight to chemical energy (complex sugar). The sugar is stored and used by the plant to live and grow.

Humans have also learned how to convert the solar energy to usable energy. We convert solar energy directly into two types of energy for use.

  1. Solar thermal (heat energy) is used for hot water and steam for power generation.
  2. Photovoltaic (solar electric) energy is converted from the visible light spectrum to power electrical appliances.

Solar Thermal Energy:

Solar Thermal energy can be used instantly and it can also be stored as hot water or oil in an insulated container. The storage is usually for no more than a day. This is the most efficient conversion of solar energy to usable energy although it may not be the most cost efficient method. Small-scale solar thermal systems require expensive equipment to capture solar energy, convert it to thermal energy and then store it for later use. The net conversion efficiency is around 30% for the average home.

  • The cost can be amortized over the lifetime of the system (15 – 20 years). Compared to heating water with electricity, the system reduced energy costs during the system lifetime. Compared to heating water with NG, the system may not reduce energy costs during the system lifetime.

Photovoltaic Energy:

Photovoltaic energy (PV) is used instantly since electricity travels close to the speed of light, although it can be converted and stored as chemical energy. Chemical energy storage such as electrolyte batteries or hydrogen provide 24-hour usage of solar electric energy. It also adds cost to the solar electric energy system. The net conversion efficiency of the average PV system without energy storage is around 13% to 16%. Energy storage will reduce that efficiency to 10% to 14%. Off-grid system net conversion efficiency is under 10%.

  • PV systems amortized over 5 to 10 years usually provide a positive return on investment. Over the life of the PV system (25 years), the return is 2x to 5x of the system cost. With energy storage added to the system cost, the lifetime return is 1.5x to 3x of the system cost.

Capacity Limiters for Photovoltaic Energy:

Peak solar hours occur during the six mid-day hours; this is when 80% to 90% of the photon energy is converted to electrical energy. This can be a problem for utilities if electrical energy is consumed during other hours of the day. Utility companies must balance the electrical power grid and provide stable voltage to their customers. A limited amount of solar electric energy can be fed into the electrical grid without causing voltage rise and collapse (around 10% of the electrical load). Increasing the capacity far beyond the 10% limit requires converting the electrical energy to another form of storable energy. Energy storage is necessary to extend the usage of solar electric energy.

  • Chemical energy storage (the electrolyte battery) is the most common method where electrical energy can easily be converter to and from chemical energy. The conversion efficiency is around 90% efficient. The cost of chemical energy storage is high, although several types of batteries are now on the market and prices are dropping. Charging the batteries requires hours for most technologies, although some technologies are faster than others. Residential systems are typically used for backup power when the utility power is lost. Commercial systems will use energy storage mostly for load stability and rate cost.
  • Hydrogen energy storage (fuel cells) is a growing technology where electrical energy is used to separate hydrogen from a molecule such as water. The conversion efficiency ranges between 60% to 90% depending on the method. The net efficiency is reduced much further if the hydrogen gas is concentrated for storage. Compressed hydrogen is very portable and lightweight. Non-compressed hydrogen would require massive storage space and would be impractical as a stand-alone system.
  • A couple of other methods of energy storage are flywheels and capacitor banks but neither have proven to be as feasible as chemical batteries or fuel cells.

Solar Electric Systems:

Solar electric systems produce around 1% of the U.S electrical energy generation; some areas of the U.S are experiencing close to 10%. Here is what is being done to satisfy electric grid stability as solar electric grows in capacity:

  • Correcting power factor problems: Most areas of the electrical power grid experience a lagging current because of inductive electrical loads. Solar electric inverters can correct some of that with their capacitors (capacitive loads).
  • Peak demand: When too many heavy electrical loads occur at one time, the electrical load demand is high, and very difficult and sometimes expensive to generate and manage. Distributed solar electric generation sites provide onsite power and reduce the peak load demand. Since rain and heavy cloud coverage reduce this capacity, energy storage can be installed to work with the solar electric system to produce power on-demand.
  • Load and cost management: Solar electric systems can be directed to produce energy during specific daylight hours when load demand is highest and/or when electrical rates are highest. Combining this with energy storage will increase the return on investment for the system owner.
  • Micro-grids and emergency power: Some solar electric systems with energy storage will be designed with extra storage capacity. These systems can operate and produce electrical power for several days or longer.

The applications identified above will allow solar electric system capacity to grow without limits.

Kelly Provence


Is Renewable Energy an Oxymoron?

In short, yes it is. Energy changes form, but it does not renew itself and an outside force cannot renew it, although it can draw energy from an outside source.

On the other hand, everything is energy and as far as we know, there is no less of anything now than there ever has been. Matter and energy are part of the same equation; energy changes form but it doesn’t cease to exist. In that respect, all energy is renewable.

What is usually termed renewable energy is energy that uses a fuel source that appears to be endless, continuous, and for the most part not found in storable state.

Fossil fuel energy comes from ancient carbon stores and nuclear energy comes from radioactive heavy metal deposits; neither of these energy sources can be replenished for our use.

Solar energy is the most abundant of the renewable energy sources. It takes about two years for a solar photovoltaic (PV) energy system to produce as much energy as was consumed to manufacture it. Photon energy is abundant but not concentrated; this requires massive area coverage. In locations where a large amount of energy is consumed, the real estate required for the PV arrays can be a serious cost factor. Using some type of building integrated PV array attachment seems to make the most sense. One major problem with solar PV energy is that is must be stored in order to displace conventional steam producing energy sources. Over all, PV energy is the most renewable source of energy we have.

Wind energy is not as abundant as solar energy but it is more concentrated. Wind energy systems require less area than PV systems but they required dedicated real estate; they cannot be integrated with existing buildings, however they can be integrated with the existing flora and fauna. It only takes about one year for a wind energy system to produce as much energy as was consumed to manufacture it.

Wind is a result of solar convection due to the earth’s rotation, local terrain and air temperature; this being the case, wind energy is variable with regard to location, time of day and time of year. Energy storage is necessary if wind energy is to displace conventional steam producing energy sources. Wind energy is probably the second most renewable energy source we have.

Hydroelectric energy that uses dams is limited to existing rivers and bodies of water. This type of energy currently provides about 20% of the world electrical power. The advantages of using hydroelectric energy are, flood control, potential energy storage, and recreation areas are created; these power plants create many economic benefits besides generating electricity from a renewable energy source. The disadvantage is mostly the effects on the ecology of the river system. The long life of hydroelectric generators makes them an excellent renewable energy source.

Biomass steam generators are quickly becoming a replacement option to coal steam generators. The limit to this renewable energy source is available land and water resource; otherwise, it has the on-demand energy delivery like coal but has a carbon-negative footprint.

Geothermal energy derives its energy from the internal heat of the earth and is an excellent source of renewable energy. The limitation for now is that it is only available in locations where the earth’s mantle is proximate to the Earth’s surface.

Renewable energy and clean energy are dissimilar with regard to the energy source. Nuclear energy is considered very clean since the emissions are produced only from construction and maintenance of the facility. The chart below shows the proportion of energy generated to CO₂ emissions for each generators lifecycle.

Courtesy of

The question of whether renewable energy is an oxymoron is a good one. As with most commonly used terms or phrases, it is dependent on a particular perspective. In my own definition of renewable energy, I consider the lifecycle of the energy generated verses the lifecycle of the energy source; the former must be greater than the latter.

If nature can renew the energy source in a period equal to or les than the period in which we consume the energy, consider it renewable.

Start your solar training classes to learn more about renewable energy. Learn more about Solairgen School of Solar Technology

Solar PV Panels on Cedar Home

Grid-tie Inverters and Generators

Grid-Tied PV Systems and Generators

The question keeps coming up; “Will a generator keep the grid interactive, non-battery based PV array operating during utility power
outages?” In theory, it seems like a logical idea since the generator operates at 240 volt 60 Hz and this is what the inverter is looking for in order to
continue operating.

The problem is, the generator cannot absorb the excess energy from the PV inverter output, nor can the generator react quickly enough
to the fluctuating output of the PV inverter. With a grid connection there is a certain amount of buoyancy or capacitance in the grid to allow for varying electrical energy.

A second problem is how the generator will react to another AC source; it may shut down or it may be damaged by the other AC source.

The solution is the same as it has been since the start of PV energy systems, battery storage. There are many new product advancements in
battery storage or energy storage and the future looks bright. For now, the best solution for backup power during a utility outage is one of two options:

  1. An AC generator can be set up as backup power with a transfer switch that senses the loss of utility  power. If a grid interactive, non-battery based PV array is operating when utility power is down, it will go into a standby status until the utility power returns to normal.
  2. Another option is to use a battery based, grid interactive PV system that can provide backup power during utility outages; a generator can be tied in with the battery-based inverter to help charge the batteries during extended cloud cover and rainy conditions.

If option #2 is your preference, you will find that battery based inverters are quite different from utility interactive inverters. If you presently have an SMA utility interactive inverter, you can add the SMA Island battery based inverter to the system and have the best of both worlds.

For other utility, non-battery based interactive inverters, you either need to change out the inverter to one that is battery based with the utility interactive feature or just use the generator as the backup.

Kelly Provence
IREC/ISPQ Certified Master PV Trainer