Solar or Generator - Which is best?

Many people have purchased generators as a way of beating the current energy crisis, but in doing so they may have sacrificed their peace of mind.  One alternative that people have considered is solar energy which is noiseless and non-polluting.  But which of these options is really better?  Not enough public education has been done on the merits and disadvantages of solar energy. 

When is it best to go solar and when should one settle for a generator?  What are some of the important things you should consider in deciding for one over the other?  It all depends on your short term and long term needs, where you live, and whether certain issues are important to you.

A Word About Solar

A common perception about solar energy is that it is expensive, but this is wrong.  For an investment that will last you thirty years or more, solar electric systems are a very good value.  There is almost no running cost and the replacement costs of some equipment such as batteries only occurs once every few years.

In home based solar electric systems, a group of photovoltaic modules (or solar panels) is used to generate enough power for the household by placing them on a rooftop or similar open space.  Batteries are used to store the energy produced and ensure that electricity is available both day and night.  The rest of the system includes equipment to control the charge level of the battery (a controller) and another called an inverter which converts the battery's energy to 220 volts AC so that standard household appliances such as televisions, fridges, and fans can be used.


A typical home-based PV system.

Solar vs. Generators

Generators provide an easy but ultimately expensive standby power source.  They are readily deployed and can supply power indefinitely as long as fuel is available.  The initial cost of a diesel or petrol generating set (genset) is also lower than a solar electric system of the same capacity.  Solar electric systems, on the other hand have a higher entry cost and can only store the free sunshine during the day.  If you run out of power at night you would need to wait until the next day to replenish the batteries.

A solar electric system may cost more to start with, but it costs very little to run.  In fact the only running cost is that of replacing batteries every few years.  Because the energy is stored, you can use as little or as much as you want at the same efficient rate.  However, being more conservative lets you run your system for a longer period without recharging.

The choice of generator versus solar depends largely on your planning horizon.  As can be seen from Chart 2, a PV system's running costs are virtually nil, while the costs pile up for running  a 1.2 kVA generator for 12 hours a day.  Maintenance costs have been ignored.  The PV system pays off against the generator after about three years.  If you plan to use standby power continuously for three years or more, you're better off with a solar electric system.

Comparing solar with generators watt-for-watt is not correct because you may need a much smaller capacity solar electric system to run the same load.  Generally, generators are designed to handle a worst-case load.  You determine the maximum load by adding the various loads in your house, and then you select a generator that is sized above that maximum.  With solar, on the other hand, you need to know the characteristics of that load in addition to the maximum. 

For example, the maximum power a fridge will draw occurs momentarily when the compressor motor starts (you can hear it start every few minutes).  The power drawn is less when the compressor is running steadily, and the fridge draws very little power when the compressor is not running.  If you were selecting a generator for your fridge, you should select one that will be able to run the maximum load of the fridge.  If you were running the same fridge on solar, it would be equally important to design for the total energy consumed by the fridge.

All Electricity is Not the Same

The above analysis assumes that electricity is the same whether it comes from solar PV or other sources.  In reality, however, each energy source has strengths and weaknesses depending on the application being used.  You can take full advantage of solar's strengths by using it as an energy source for specific applications.  Generally, solar is best suited for lighting and electronic equipment, and less suited for heating and heavy motors.  An energy expert can help you determine which appliances in your home are best for solar and which others can be run by other means.

The table below shows specific applications and the possible sources of energy for each type of appliance.  A proper comparison of energy sources should take the type of application into account.  Such an analysis will be the subject of a future article.

ApplicationPossible energy sources (from best to worst)LightingSolar, grid, generator, candle, torch, gas lantern, firewoodCookingGas, charcoal, grid, generator, solar, firewoodSpace cooling and heatingGrid, generator, solar, evaporatorEntertainmentGrid, solar, generator, batteriesNon-economic factors

Photovoltaic technology provides additional environmental and social advantages over other energy sources such as gasoline fuels.  Some of the advantages are:

• Solar delivers free energy

• There are virtually no maintenance costs

• There is no pollution during operation

• No noise emissions

• Solar provides power for many applications

• No dangerous fumes or fire risks

• Simple and reliable service both day and night.

And the winner is...

If you already purchased a small generator for your home, don't go and sell it yet.  You can still take advantage of solar technology by combining your generator with solar and mains (ECG) in a hybrid system.  For people with air conditioners and other high-consumption equipment, you might be better off using a generator for those because the cost of a solar electric system to run those appliances may be prohibitive.  However, everyone should consider using solar electricity for lighting.  There is no point wasting fuel and firing up your generator just to keep a few lights running.

Yes, the initial cost of solar is high, but you get the advantages of low running cost and a system that is modular and expandable.  You can start with a small system now and add on to it when you have the means.  Solar is an energy solution that goes far beyond the present energy crisis.  It is a solution that will keep saving you money for many years to come.