Is Solar panel power equivalent to generator output?

mobilesport

Will a 1000 watt of solar panels put out the same amount of power as a 1000 watt generator given that the sun is out in full (no clouds and wired correctly?

JoshK

Welcome, I'm pretty new here too, but here's what I have learned... Down by the equator, probably. Here is South Dakota, maybe 860 watts from the panel with no clouds. Then another 10 to 15% loss for the inverter. (I believe gas engines have a dismal 25% or less efficiency, but that would be figured in to the rating.) The great thing about the inverter is you can vary your fuel consumption for loads like a refrigerator or pump. The generator would keep running and suck significant fuel at all times. Another great thing about the solar/battery/inverter setup is that you can sleep with it running.

BB.

Solar panels do generate electricity--But the way they generate it vs how we use it make solar panels, by themselves, a poor analogy to power from a generator.

The common ways of using solar power:

1. Grid Tied System--Solar panels + GT Inverter connected to your main electric service. You really cannot tell the solar power is there, except your utility bills are reduced (utility meter slows down, or even turns backwards). GT Systems do not provide backup power if the utility mains fail (there is at least one notable exception).
2. Off Grid System--Solar panels + charge controller + battery bank + DC loads + (optional) AC inverter. Think of your car's electrical system. The car engine charges the battery when the engine is running, and the battery supplies power when it is not. You can play the radio/turn on the lights/etc. if the engine is running or not (until you run the battery dead).
3. Specialized Solar Power--There are other ways of using solar electric panels. One common method is to connect solar panels to a water/well pump. The pump spins when the sun is up (faster at noon time, slower dawn/dusk). Using the nature of electric motors and (optionally) specialized electronic controls, the solar array can pump water to a cistern/tank/pond without the use of backup batteries. Other systems include devices that can do both #1 and #2 with the same hardware.

Solar electric panels are not like standard batteries. Batteries are a "voltage source". And Solar Panels are a "current source". If you have not worked much with electronics/electrical systems before, it takes a bit of studying to understand the differences.

Basically, a battery bank can supply a "fixed" voltage with varying current (12 VDC or 120 VAC are both voltage sources, as well as the standard generator set). Solar panels output a constant current (based on the amount of sun hitting the panel at that moment) and the output voltage can vary from zero to ~18 to ~21 VDC (for a "12 volt panel")--This means that the loads must be able to work with varying current and voltages from the solar array.

There are devices out there that are current sources such as Arc Welders (transformers and welding generators) and power supplies for florescent & LED lamp fixtures.

For how much power a solar panel can generate... The basic math looks something like this.

The amount of sun per day that we get varies based on our location, seasons, and weather... More or less, from ~2 to 6+ hours of sun per day (winter is usually less, and during stormy weather, solar panels can output only ~1% of their rating or less). For many places, we get roughly 4 hours of noon time equivalent sun per day for a minimum of ~9 months a year.

For a GT system, that would be:

• 1,000 Watt solar array * 0.77 solar panel+controller derating * 4 hours of average sun per day = 3,080 WH per day = 30.08 kWH per day

For a typical off grid system, the maximum energy per day would look like (more losses due to battery bank + AC inverter + Charge controller, etc.):

• 1,000 Watt solar array * 0.52 system efficiency * hours of sun per day = 2,080 WH per day = 2.08 kWH per day

A Honda eu2000i (1,600 Watt peak) generator at 1/4 load (400 watts) would generate on 1.1 gallons of gasoline:

• 400 Watts * 9 hours (per 1.1 gallons of gasoline) = 5,400 Watt*Hours = 5.4 kWH per tank

For short term / occasional use of power, a generator is frequently a better/more cost effective source of energy. For living off grid (9+ months of the year, or for weekend use of s small amount of power to charge cell phones, run LED lighting, radio, possibly laptop computer), then off grid solar can be a good solution.

For remote use (well pumps for cattle, etc.), then solar can be cost effective too--Where it simply costs too much to connect to the utility/grid.

-Bill