What is the best solar panel?

[GDunk]

Q CELLS DUO BLK ML-G10+ 400, Panasonic EverVolt H series Solar Module 400-Watt, or SunPower?

[GDunk]

We bought a newly renovated condo so little room for greater energy efficiency. “I built to 5x electric use” I find interesting. I’m exploring solar proposals that are 5-10% above current use. I would like the ability to expand panels in the future should demand require this.

[bcroe]

We are reviewing proposals that are sized 3-5% over current energy use. Yet these panels denigrate efficiency over time. In 10, 20, 25 years where will we be? Shouldn’t they be sized appropriately to take this into account?

Here for decades, there have regularly been found ways to cut
energy use. Could be better energy star appliances, better
ways to use them, more insulation. Unless your place is
already built to latest, most efficient standard, you likely will
find ways too.

Some power cos do not limit your system to your recent past
consumption. I built to about 5 times electric use, because
the HVAC would be converted from propane to heat pumps.
With good results for a decade now, heat and electric total
are about $15 a month.

A net metering solar system often is rated by inverter AC
output capacity. With a string inverter system, you might be
able to plan, how to add a few panels to the existing inverters
(as I have done), no change to AC output rating.

Realize with all the variables, system performance is not
going to be very predictable in the second decimal place.
Bruce Roe

[jflorey2]

We are reviewing proposals that are sized 3-5% over current t energy use. Yet these panels denigrate efficiency over time. In 10, 20, 25 years where will we be? Shouldn’t they be sized appropriately to take this into account?

I'd say no. Instead I would just add panels when your production drops off in a few decades. You won't need many; degradation is slow, under a percent a year.

Or just slowly invest in more efficient appliances as your existing ones wear out.

[GoingElectric]

I live in Massachusetts where net metering is mandated. We have a 3-story building with a flat roof, so no obstructions. Proposals now from Panasonic, Waaree, SunPower, Qcells. Any recommendation? Inverters are Enphsse, SunPower, Solar Edge HD Wave. How much over current electric use should this be sized for? Currently I have proposals from 103%-109%.

Since you are free of obstructions (no chimney or vent tube either?), a single String Inverter is an excellent option. Optional "Optimizer" may not be needed either.
Most installers are jumping on the microinverter bandwagon for everything when in a String Inverter would be more cost effective.

As for panels, the Q-cell are most attractive to me right now
For example Q.PEAK DUO XL-G10/BFG
Do NOT get a the "BLK". AVOID!! It has "cosmetics" that make it look nice, but that reduces W and Life.

Also the "Bi-Facial glass (BFG) also increases power out.

[littleharbor2]

We are reviewing proposals that are sized 3-5% over current t energy use. Yet these panels denigrate efficiency over time. In 10, 20, 25 years where will we be? Shouldn’t they be sized appropriately to take this into account?

All depends on what your production goals are. If you are aiming at staying in the tier 1 billing area due to a poor reimbursement plan from the POCO. it makes little sense to overproduce.

[J.P.M.]

We are reviewing proposals that are sized 3-5% over current t energy use. Yet these panels denigrate efficiency over time. In 10, 20, 25 years where will we be? Shouldn’t they be sized appropriately to take this into account?

Among and along with other considerations including your situation and preferences, yes.

[azdave]

No. The goal is not to make sure that in 25 years you are still producing the same as your actual needs were 25 year earlier besides, many utilities will not allow you to install more capacity than your historical use from the last 3-5 years. My contract is that way so I could not add a few more panels to make up for future system losses or consumption increases. Just be happy you can match you current needs reasonably well and then hope the utilities don't change the rules after you've signed a 20-year agreement.

[GDunk]

We are reviewing proposals that are sized 3-5% over current t energy use. Yet these panels denigrate efficiency over time. In 10, 20, 25 years where will we be? Shouldn’t they be sized appropriately to take this into account?

[J.P.M.]

It is also very useful for comparing panels. Imagine the unholy mess it would be if everyone used a different insolation/temperature/backpanel illumination to test their panels and provide a power rating.

Indeed ! And, agreed.
Never said, implied or meant for anyone to infer otherwise.

BTW, if talking about panel testing standards, the commonly accepted term when dealing with power or power flux (W/m^2) is irradiance. Insolation has a time dimension as in kWh and is used when discussing or measuring energy. Panel testing deals with power, not energy.

[jflorey2]

Any panel testing standard has nothing to do with real world performance under day/day conditions.
Uniform testing standards' best use is for system design which is also why it's best to have one system for panel rating.

It is also very useful for comparing panels. Imagine the unholy mess it would be if everyone used a different insolation/temperature/backpanel illumination to test their panels and provide a power rating.

[Old_Man]

Then I see STC, a new term for me, so I look up
“Standard Test Conditions”

To this old pilot, "STC" will always mean "Supplemental Type Certificate."

[J.P.M.]

True, STC has nothing to do with real world performance. It is merely a level playing field all panels are tested on for comparison's sake. Of course most arrays won't produce at their STC numbers although some folks at high and cool elevations CAN see higher than STC numbers from their arrays, proving that STC numbers aren't entirely misleading.

Any panel testing standard has nothing to do with real world performance under day/day conditions.
Uniform testing standards' best use is for system design which is also why it's best to have one system for panel rating.
STC has fewer complications. In that sense, PVUSA violates the KISS principle.
Everyone on the same page with the least complicated testing system seems best to me even if some folks need to read a data sheet and actually learn what they're comparing.
Having different standard testing methods (I think perhaps that's an oxymoron) leads to the situation like that now going on between EV range rating differences between U.S. and European versions of how it's done which can lead to easily avoidable and unnecessary confusion which usually means more bureaucracy as well as more money for those with equipment to (oversell)sell to more confused users.

[GDunk]

I live in Massachusetts where net metering is mandated. We have a 3-story building with a flat roof, so no obstructions. Proposals now from Panasonic, Waaree, SunPower, Qcells. Any recommendation? Inverters are Enphsse, SunPower, Solar Edge HD Wave. How much over current electric use should this be sized for? Currently I have proposals from 103%-109%.

[littleharbor2]

Agreed - but - it really doesn't matter, since you can calculate the panel's performance at any given temperature as long as you know the tempcos and the performance at _any_ temperature. 25C is as good as 45C. The critical issue is that all panels be tested the same way, and that's what STC is intended for - since it's relatively easy to flash every single panel at 25C.

True, STC has nothing to do with real world performance. It is merely a level playing field all panels are tested on for comparison's sake. Of course most arrays won't produce at their STC numbers although some folks at high and cool elevations CAN see higher than STC numbers from their arrays, proving that STC numbers aren't entirely misleading.