New PV system. What is your experience with different panel manufacturers?

I am about to pull the trigger on having a 5.9kW system put on our home/office, but honestly PV systems are kind of outside of my realm of expertise (I mostly work within air sealing and insulation retrofits). I would like to hear from people in the PV word about their experience with the hardware that is out right now.

From my research the SunPower brand PV panels and inverter systems seem to keep floating to the top of the quality list. I like the fact that their systems are modular and they seem to have a good warranty. But I want to know if there are other PV panel manufacturers that are of similar or even better quality. And is it actually realistic for an unobstructed SE facing 5.9kW system to generate 16-20 kwh per day in SC? And from your experience is this a fair quote?

Here is a snapshot of what we are looking at having installed: 5.9kW Sunpower system = 18 panels, 1 6000w inverter, Unirac roof mounted, grid tied sell all connection to an existing meter location. Quote is $30K for hardware and install, and all permits. (This is the complete cost not counting any Fed or state rebate programs).

Tags: PV, solar

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No better time than now.  Go for it. I am worried that net metering may soon be gone. Grandfather clause is a nice friend to have.

Don't believe that?  Take a look at what is taking place in San Antonio:

I have 4.9 kW of Evergreen ESA-205 modules that have been in place for four years without any difficulty. SMA 6000 inverter. Excellent performance from both over the period: power production was 7,400 kWh over the year.  System was expanded to 5.9 kW in the last year...I've been a zero source energy now for an extended time, even charging a Chevy Volt at home (averaging 6 kWh per day for that end-use.)


On-line data:


Danny Parker


Hi Danny,

That is great information, thank you very much. i had not heard that news out of San Antonio either, that was rather disappointing.

When you upgraded to 5.9kWh did you have to introduce a new inverter, or did you already have a 6000w inverter from the original install? And how did you generate the attached graph JPG that went back to 1989? that is fantastic!- Jason

Hi Jason,

Already had the 6000W inverter, so it was just a matter of expanding the number of modules on the racks.

Generating the graph was simple: I kept all the utility bills since I moved into the house in 1989 and then logged the power production of the PV system (you should make sure to do that). After that it was just spending a day with a plotting software with my records of what I had done at the house since we moved in. Yes, I spent a ridiculous amount of time on that, but it was fun.

My sister has a 6 kW system in Fremont, CA, now too and my brother in law just sent me their utility history-- they are headed down towards zero electricity.

Oh, another reason to get PV installed soon: can't imagine with all the utility belly-aching going on now that the tax credit will last more than a couple of years more.

Navigant research shows solar PV reaching grid parity EVERYWHERE by 2017, so this train is really unstoppable.  Until then, however, expect a lot of fireworks.

- Danny

Hi Danny,

You kept your energy bills all the way back to 1989?, that's slightly OCD...but in a fantastic way! I really like the graph you generated with that info, and I will heed your advice on logging the power production.

The whole reason for considering this system was the price of hardware is really low, and credits and accelerated depreciation deals cant stick around forever. When you can buy a $30K system and get $23k back in credits and depreciation within 12 months...that is pretty compelling as far as business decisions go.

- Jason

We have ours going back during that time also.  Quicken, scanners and document organizers.  We might be a little bit obsessive we track things down in under one minute intervals...  but if you are doing a science/research project -- your own house can be a great resource.  You know the habits of the occupants, their vacation schedules, choice of foods,  and names of the pets.  All things that might make a difference when you analyze the data.

You fellas had me curious about how far back I could go with my energy consumption records. I found that I could go back as far as I owned the home, and with special permission I can go back further. That is quite a wealth of information that I never even thought about tapping into. Danny and Dennis, are you both educators in the field of energy conservation? I can see how this type of information can be very useful in educational sessions.

I am a relatively newby (really concentrating on efficiency),  perhaps seven or eight years now.  I spent years reading papers by Danny... :-)

My early, early, introduction into renewables and the world of energy go back to nearly the first earthday  and a world energy simulator that was taken around schools in Montana by Dr. Amend(?)  It was an analog simulator that allow students to compete against each other trying to not overheat the earth, stretch the resources, and still grow the economy -- even as the world population was growing.  

Even 40 years ago - it was EXTREMELY challenging to not have the game "end" in 2020 or 2030...   We (the world) has adapted - and we continue to adapt.

The energy use bills can provide some really good insight into your appliance use, habits, and where to direct additional spending to save money in the future.  For years, I'd blame the higher energy costs on the electric companies, but after looking carefully at the bills it becomes apparent that the real cause was increased consumption.  Long term trends make that easy to spot.

I should add, since the thread was about solar PV.  I have both Sharp and Solarworld panels on my roof top.  AC output peak is around 9kW.  Spring/Summer I can produce 60kWhr a day.  Washington has net-metering - so I use that to bank energy for most of the year.

I'm in the always rainy Seattle area.  That meant designing the system not for optimal year round production, but instead selecting to maximize production from March through October.  The panels have a shallower angle, and are turn toward the ssw.   Early morning we often see fog or moisture vapor rising outside.  So I am to maximize the afternoon and evening production.

I loose perhaps seven or eight percent over the "idea" location of same lattitude.  But I gain because the panels are set to work for the local climate conditions that the simple solar calculators do not understand.

I also choose to use enphase microinverters.  With neighboring trees a shadow is always possible -- especially in the winter time.

Summer time I can produce 1300kWhr+ easily.  December or January, that drops down to about 175kWhr.  Still a reduction of electricity from the grid.

The power I produce during the summer time - never leaves my neighborhood.   I can hear neighbor's air conditioners, TV's, and stereo's cheerfully using running on solar power. :-)

Hi Everyone,

Yes, I do think it is very helpful to keep your utility records.  In fact, I firmly believe that simple analysis of your utility records can be more illustrative than a lot of simulation (and I love simulations).

Key concept with a year of utility records: find your lowest month for electricity and natural gas that was NOT a vacation month. Subtract that value from all other months. The result is your heating and cooling by month. The residual is your base load.

Higher electricity consumption in summer months is air conditioning; higher natural gas (or electrical if a heat pump) consumption in winter months is space heating.

Even if you have gas heating, you may see your electrical loads higher in winter months. In December this is likely from holiday lighting, but in other months much of that is likely coming from a combination of increased blower energy and lighting energy.

Base loads for gas are typically cooking (if gas) dryer (if gas) and water heating-- although water heating does vary somewhat seasonally.

High electrical base loads are often refrigeration, electric dryers, lighting and pool pumps (the later end-use is so big that it is in a class by itself).

Doing this from year to year will allow you to track how things are changing and also how effective measures are that are being installed.

It's an effective technique-- even if fairly crude. Most importantly, you are seeing what you used and paid for and examining trends will provide insight as you work your way down to lower energy use.

If you want to use an energy simulation such as EnergyGauge or BEopt, then it is useful to tune them to your actual space heating and cooling before seeing what insulating the lid to R-49 might do...

Relative to PV, it is useful to note how much you are paying per kilowatt installed DC. Generally your production will be 4-5 times that that value per day. So, if you cost is $5000 per kW installed, your cost to produce a kWh per day is about $1000. Thus anything that will reduce your consumption by a kWh per day for less than $1000 (or a similar rate) is important to do before you put PV on the roof.

A good example: say you have an old side-by-side frig, using 4 kWh day (measure with a kill-a-watt). That is silly to serve its load with PV. You can buy a brand new EnergyStar frig at Sears for $1000 and save 2.5 kWh per day. That is 2.5 times more cost effective than adding PV to cover the use of the old frig.

All the Best,


Hi Danny,

I do have a freezer that is about 15 yrs old in the garage. I know it is my "low hanging fruit" to all of my consumption. I keep it because I garden and hunt and I keep it full with the fruits of that labor. I have measured it with a kill a watt and it consumes 90kWh per month during the spring months. Probably more in the summer and less in the winter. That one appliance is removing almost 4 days of PV electricity production each month.

Looks like I should head over to the Sears Outlet and see if I can do better. I'm sure I can.


I work for an electric utility and do a lot of work with our customers that generate solar power.  SunPower makes a great module.  They are one of the most efficient solar modules (20%), which means it takes fewer modules to generate the same amount of power as other solar modules.  Because they are more efficient, they tend to be more expensive than standard solar modules, but you get some of that back from lower installation labor and racking material costs.

Rather than focusing on kWh per day, I prefer to work in "equivalent full sun hours" (EFSH) per year.  It is determined by dividing the total annual kWh of actual generated electricity by the kW rating of the string of solar modules.  This EFSH takes into account shading, dirt on the solar panels, cloud cover, inverter efficiencies, temperature effects, etc.  To determine your expected annual kWh production, simply multiply the kW rating of your array times the EFSH for your area.  I would expect South Carolina to be at least 1300 EFS hours per year, which means your system should generate around  7,670 kWh per year (21 kWh per day).  This figure is for a fixed array, with NO shading.  Make sure there is NO shading on any part of the array; no vent pipes, no chimney, no partial eve shading, no tree branches, etc...

Here in sunny eastern Washington (state), we typically measure 1,200 hours of EFSH. A system in rainy Seattle can expect around 1,000 full sun hours per day. I believe Germany is around 900 hours.

Thank you James,

I may be able to get some EFSH readings from my installer of similar 6 kWh installs they have done. Granted the numbers wont match exactly because every install is different, but I can see how calculating the EFSH gives true apples to apples comparison. - Thanks - Jason



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