Someone is given $10,000 to spend on either a grid-tied PV system or on compact fluorescent lights. Their goal is to save energy, reduce CO2 output, and delay the building of more power plants. Which option is better, PV or CFL?
Here are a few assumptions. The CFL is replacing a 75W incandescent light which runs, on average, 4 hours a day. Also assume that the CFL draws 15 watts, 1/5 the power of the incandescent bulb for the same lumens. Finally, assume that you install the PV system in sunny southern Arizona with a net production output of 1,650 kWh/y for each kW of installed rated power.
With the $10,000 one can buy a 2kW grid-tied PV system ($5/w), which will produce about 3,300 kWh/y of usable power. If the PV energy is offsetting energy from a coal plant (like in Tucson), about 3.3 tons of CO2 will be saved a year. But it will not help reduce peak load much since the utility can't count on its availability with the level of certainty they demand. (see post "Grid Tied PV and Peak Demand").
If one chooses the CFL, then the $10,000 will buy about 5000 lamps. Each lamp saves 60W for 4 hours a day (75W - 15W). 60W x 4 hr x 365 days x 5000 lamps = 438 MWh/y. This reduced CO2 by about 438 tons a year. But also very important, efficiency gains reduce peak load requirements and can delay or avoid the construction of a power plant.
So the CFL options saves 132X more energy, reduced 132X more CO2 per dollar, and easies the burden on the utility grid and generation loads.
So why don't utilities give away free CFL bulbs to anyone that asks rather than subsidizing grid-tied PV?
The point is that there are many things which can and should be done in the areas of energy efficiency before one spends any significant money promoting grid-tied PV. But it is not happening and the reason is a mystery.