I hope some of my readers will be knowledgable enough to help with information about a small solar power installation. I don't want a whole-house, major-league installation: just enough to charge a couple of power stations in case of need, and perhaps an additional storage battery in due course.
I note that most of the solar power vendors want to charge several times the actual cost of the solar panels, which can be determined easily enough through looking at importers' prices. I object strenuously to being "milked" like a cow for all the money they can get out of me! In particular, many of them won't sell solar panels alone - only as part of an overall "solution" that's far more than I either want or can afford.
I'm looking for panels that can generate 500W-1,000W on a good, clear day, although I can go a bit higher if necessary. I'd prefer to use 2-4 panels, but not more, for ease of portability. They'll be mounted on a frame (fixed or on wheels) in my back yard, not on the roof. They have to conform to these specifications:
- Total voltage:12-150V.
- Total power: 3000W max.
- Uses MC4 connectors or adapters.
If I need to reduce the power to charge smaller power stations, or to connect the panels to a power station for charging it, I'll also need the necessary equipment to do that. They'll be used with Ecoflow and/or Bluetti power stations ranging from 500W to 5,000W in capacity.
If any reader can advise a reasonably good quality solar panel/s to fit that need, please let us know in Comments. Please also advise on the type of frame that would be most suitable for the back yard, but would allow the panels to be brought under cover or otherwise protected when a Texas hailstorm arrives. (Those are no fun: right now, as I write these words, a team of roofers is stomping back and forth over my head, replacing our shingles as a result of a hailstorm last month.)
Also, if any reader can recommend a good introductory text, or video, or Web site to help me better understand the ins and outs of solar power, I'd be grateful. Right now, I know only enough to be dangerous. Thanks!
Peter
joels gulch has been on solar for several years. he should be able to help.
ReplyDeleteI don't know if this is helpful, but The 8-bit Guy did a couple of videos of his solar setup he has and I think it might be helpful for you:
ReplyDeletehttps://youtu.be/RhTDneoDUdc
If you get good advice, please share what you learn in a blog post.
ReplyDeleteharbor freight has relatively inexpensive panels and parts
ReplyDeleteIf you are going for a simple setup
From what I've read here and there, the majority of solar panels are made in China. And they are not considered very good or long lasting.
ReplyDelete
ReplyDeleteYou need to tie down the voltage you want to achieve a bit closer than 12-150V. Most likely best for you would be 24 or 48 V.
Panels can be had in those voltages, both are standard.
Your charge controller would be the thing that makes or breaks your system. It appears the battery banks you have referenced will take pretty much whatever voltage you give them and have their own internal charge controller. If you want your own battery bank rather then the poser stations then you'd need a charge controller. Note that if you are not gonna travel then the battery bank/inverter is a better way to go than the more portable power stations.
My suggestion would be to choose your panels and have a local fabricator/welder make a framework with whatever wheels you want for the panels. Leave the option for some way to tie them down or weigh them down as the winds are a factor in large panels. Possibly two or more smaller carts would be better than one big one, you can always parallel the panels together. Remember that you will likely need to take them indoors, so the total size should allow you to move them through a doorway. Panels like this are about the size you need:
https://signaturesolar.com/preorder-boviet-450w-bifacial-solar-panel-silver-up-to-540w-with-bifacial-gain-bvm6612m-450s-h-hc-bf-dg/
or
https://www.gogreensolar.com/products/solar4america-550w-solar-panel
So you'd need minimum 6 panels paralleled to get you the wattage you want.
Figure about $0.50 to $0.75 per watt at todays prices for the panel, plus a frame and wheels and leads.
Bigger panels are harder to handle. 500 watts is about 8' x 4'
Just something to think about.
I would look at the solar panel-powered fence charger setups that are used in ag and small scale livestock. Those usually have panels, batteries, and auxiliary hardware. The systems are typically small, robust, and portable.
ReplyDeleteMy first stop would be to see what Gallagher or Premier1 are offering.
Make sure you have lots of sun even in the winter. I have 5 panels 200w ea like those used on campers. April and May are my best months otherwise trees and a low sun cut production. I save about $75 a mo on my electric bill those months. I have a Bluetti 2k watt battery. Set up was super easy.
ReplyDeleteTheses folks helped me design our RV's solar setup, good folks, good prices and very easy to work with. If nothing else grab their free catalog and design guide.
ReplyDeletehttps://backwoodssolar.com/
Questions:
Do you want 120 volt AC power?
Do you just want to charge batteries?
How many volts in each string?
Reliable AC power from panels really requires a battery bank and inverter. Maybe an inverter/charger if power is coming and going.
Battery banks need a charge controller, a basic one will work but a MPPT (tracking) one will get more charge out of your panels.
For portable I'd avoid any glass panels, they are too easy to break if flexed and not repairable. Backwoods has a selection of mounts that might work for you.
Basically, I think the fundamental concerns to focus on are getting them from a a company that has been around for a while and looks like it is going to be around for a while longer. A problem a lot of people seem to get into is that the Chinese suppliers appear and then vanish after a few years, and so parts are not available for repairs in 5 or 10 years when you start to need them. Further there are a lot of installer who were roofers last summer and will be roofers again next summer, after installing the panels on "your" roof taught them it's more complicated than they thought. You want a company with experienced installers who will warranty their work.
ReplyDeleteYou'll probably pay a bit more up front, but I believe it'll make you happier in 10 years.
I recently did a lengthy series on that subject, and although my aim was a whole house setup, there is some good information there.
ReplyDeletehttps://areaocho.com/category/prepping/electric-and-power
I've done solar systems in the past, but a lot of my information is out of date. The last system (3.6Kw; 12 panels, Trojan golf cart batteries, and an Outback Power module for charge controller/inverter) was completed 2019, and things have changed a lot.
ReplyDeleteNot sure if any US vendors are still making panels. I got my last batch of US made panels from Platt Electric, and they were at a closeout price. An earlier system used Kyocera panels from Japan (circa 2016), but they didn't show up 3 years later. Back in 2000, Siemans did panels...
An outfit that sells systems as well as the modules and small bits and pieces is in northern Arizona. I've used them since 2000 with success. Not always the cheapest, but good service and I've been happy with my (careful) selections. https://www.solar-electric.com/ Now called NAZ Solar Electric. (was N. AZ Wind and Sun previously.)
For mounts, look at Iron Ridge. They have rails that can mount on pipe or tubing, and a suitable rack could be fabricated--see your friendly ranch welder. :) I'd use either a wheeled base or a sled arrangement. I've also used angle iron and 4 stainless "zee" pieces to mount a one-panel system for my garage.
I've had good experiences with dealing with this company, try wellbots dot com.
ReplyDeletesignature solar in Sulphur Springs, TX is your best bet. Biggest issue you might face is that panels larger than 100W must ship commercial freight. I have a 4.8kW hybrid system with a 1000AH lifepo battery bank, most of the components came from signature.
ReplyDeleteGriz in East Texas
Hi Peter,
ReplyDelete15+ years off grid here.
Batteries are the key. Figure out how much storage you need. A good "starter" kit would be some Costco deep cycle golf cart batteries. I would recommend 24 volts for the DC side of the system. Minimum 4, 6 volt t-105 size batteries. If you can afford get 8 batteries.
Solar panels are now a commodity, shop around for best price. If you buy online, shipping can be problematic as the panels are delivered by truck. Most of our panels are REC brand (375-425 watt range). Quite frankly, I haven't seen a problem with Chinese panels. Stay away from Harbor Freight or Costco panels. 6 panels is more than enough to charge a battery bank as mentioned above.
Charge controller...Outback MPPT controllers is all we run. Very reliable. The nice thing about MPPT is you set your panels up for higher voltage which allows for smaller wire. Say you have 6 375 watt panels. They run about 36-39 volts. If you hook them together you get around 100+ volts (DC). Look up OHMS law, basically higher voltage = lower amperage through the wires. The charge controller will then convert the voltage to your battery voltage EG 24volts.
That takes care of the DC side.
Then you will need an inverter to convert DC to AC. Outback or Trace are some of the best.
I forgot, ground the panels. Get a DC breaker to shut off power from panels to controller and another from batteries to inverter (shut off for lightning storms).
The whole thing is actually within the capabilities of your average handyman.
Good luck!
I like these:
ReplyDeletehttps://www.amazon.com/Renogy-Monocrystalline-Solar-Compact-Design/dp/B07GF5JY35/ref=sr_1_9?crid=QP1SRNEHBHPK&dib=eyJ2IjoiMSJ9.iR1f09as4xxaz3lkPb4KJogZIH10GRYcu9gPduUQFRDRViUNkdQkSYRSnvwqQDGeZYdTOqPULFhb7RVNlPJDvM9acfSS1GHi9WbZsj-WbByWubAP7V5qGi3uZhDrcGKTtjYccEvkbMO0i82N0JDf6lnvlOmraO6qOBkcUTpPf7VtIFoiY3ILLSrfHEeosaDDWAO3MPLTlwaFZSJF-XhHmXYtZX4jHER51QOjzs0YSBE.YJ-vrl1eoG3p3Jt-sNNMibtsLZa4VaQLRepms_GgK1s&dib_tag=se&keywords=solar+panel+rich&qid=1715797155&sprefix=solar+panel+rich%2Caps%2C192&sr=8-9
I have 8 on my RV. 6 years old, rain, hail, lots of driving, they still all work like a charm.
A friend built a simple movable rack using a steel bed frame that had wheels. I think he upsized the wheels to make it easier to roll. His objective was to be able to reposition the panels a few times a day to maximize power, but it would work just as well for moving them indoors. I don't recall how many panels fit on his rack, maybe only three 200w panels. A good fab guy can build anything but watch the total weight!
ReplyDeleteHe used welding cable to minimize power loss to his cabin. This is expensive, heavy, and difficult to drag around, but be sure not to undersize the wire.
You might consider Anderson Powerpole connectors near the panels so you can disconnect the cable when you move the panels. amazon.com/dp/B0CMJZ193C Installing the Anderson involves crimping lugs onto the wires.
For smaller size wires you can use a hammer crimper, amazon.com/dp/B09M3T3PYQ
For larger sizes, or if you're doing a lot of this, a hydraulic crimper is best, amazon.com/Hydraulic-Battery-Terminal-Crimper-Crimping/dp/B06XR8BY65?th=1
best of luck,
Don in Oregon
Someone mentioned disconnect switches, I use this type: amazon.com/dp/B07XTDSD4B
ReplyDeleteDon in Oregon
Check out Renogy dot com as they have kits. I have used them for several assorted projects and have been well satisfied. As others have mentioned the charge controllers etc are key. A good pure sin wave inverter is well worth the money. A direct DC system? I don't know. BTW prayers for you problems at the moment.
ReplyDeleteI did solar on my RV for a few years, it works.
ReplyDeleteI'd see what I could learn at Cheap RV Living,
https://wordpress.casacrm.io:8443/cheaprvliving/blog/ this is the blog not the YT channel.
There is knowledge to be gained there and solar IS magic!
You might check out a YouTube channel, "Ambition Strikes".
ReplyDeleteA super simple and easy to understand explanation of a typical 12vdc system that I direct anyone who asks similar questions to:
ReplyDeletehttp://marxrv.com/12volt/12volt.htm
I second the Backwoods Solar recommendation. Never dealt with them personally, but have heard nothing but good things.
See also: https://sunelec.com/
I purchased some panels from them a few years back when I was in Fla. Since I paid in cash at the time of purchase the sales guy even knocked off 10%.
First time commenter. Long time reader. Peter stay away from this for a few more years.
ReplyDeleteThat's a BIG topic!
ReplyDeleteYou get what you pay for. If you go cheap you'll get Chinesium - low quality, short lifespan, lying specifications rubbish. eBay and Amazon ads look good but in reality your "400W solar panel" at a bargain price will be around half that AT BEST and panels are rated under optimal conditions which isn't most days.
Ditto for batteries - Chinesium.
Buy quality products like Renogy and you'll get what you paid for. 400W is actually 400W, not 200W. Yes, you'll cry at the cost, but you buy once not twice AND you get a real warranty with real support. Flexible solar panels are the way to go - lightweight and deployable. All you need do is build a light supporting frame for when you trot them out. Make it adjustable so you can point the panels at the Sun as it moves, maximising battery charge.
If's a big topic but hope this helps.
When you are building your system try for as high a DC voltage as you can. Doubling the voltage means half the current for the same power (P=IE) and and a quarter the resistance losses (P=I^2R.) Going from 12VDC to 48VDC for your batteries drops your resistance losses (heat) to 1/16th the original value and allows you to use smaller gage (cheaper) wire to boot.
ReplyDeleteDiveMedic's write up on Area Ocho is first rate, starting there gives you a good basic grounding in solar power.
"Bus Grease Monkey" on u-tube has equipped several bus conversions along with his large Quonset hut type garage with solar panels.
ReplyDeleteHe bought used commercial panels that get used for a couple years or so, and then replaced by new panels to optimize power output for commercial setups.
Commercial panels are rated for hail stones. I think 3 inch is the minimum spec for normal use, but may go larger for some applications.
IIRC, the re-seller is located in a small city on the south border of the Phoenix metro area.
He has videos detailing what electronic equipment they have used for both the mobile and fixed installations.
Hi Peter. Lots of comments, but don't see many that actually answer your question.
ReplyDeleteI've just finished building my portable power station and am still working on the solar setup, so I'll share some of what I've found.
I don't know which specific EcoFlow and Bluetti systems you have, but the couple that I looked at have similar DC input specs.
EcoFlow Delta 2: 1600W Max, 11-150V, 15A Max
Bluetti AC200L: 1,200W Max., VOC 12-145VDC, 15A
To have 1 set of panels that can cover both, you'll want to use the Bluetti specs. Of particular note is the 15A max input. This will determine how to connect your panels together (series vs. parallel or a combo - more info in a link below), and also the wire size for getting the power from the panels to the power stations.
Wire size depends on amperage and length. For a 15A application, this can vary from 14AWG for under 6 ft to 6AWG for up to 60 ft (see link below). I highly recommend oversizing by at least 1 gauge for shorter runs. Just know that you have a cost/weight penalty up front, but much better performance and longer life.
It sounds like you're really planning on permanently mounted panels. You have some choices to make here - fewer larger panels (400W+), or more smaller panels (100-200W). There are plusses and minuses to consider. Larger panels are going to be more efficient and require less thought on the series/parallel connections, as well as an easier to design/fabricate rack. On the minus side, you really have to prevent shading, as partial shading basically shuts down the panel. Larger panels are heavier (duh), but the total number of smaller panels to equal 1 large panel will likely weigh more (frames add weight). Smaller panels have more connection points, which give more chances for failure. If you don't need portability (as in take it to another location, not just moving it around in the yard) larger panels are likely the better bet and more Watts/$.
For panel sizing and brand recommendations, check out https://www.mobile-solarpower.com/ He has specs/designs and background info including reviews/testing (also has a youtube channel - look up Will Prowse). This should go a long ways towards getting the panels spec'd and selected.
For the rolling frame, check out the setup in the wiring video below. It's pretty simple and a handy friend can help you put it together in an afternoon. It's easily doable by 1 person, but I'm keeping in mind your physical limitations.
Wire gauge spec chart:(http://assets.bluesea.com/files/resources/newsletter/images/DC_wire_selection_chartlg.jpg)
Series vs. Parallel wiring of your panels: https://www.youtube.com/watch?v=OZvrTuhJhXs
This should get you most of what you need to get set up. As I said earlier, I'm still working on the solar part of my backup system. Lots to learn.
ReplyDeleteRoam over to 'https://urbansurvival.com/' and send an email to George.
He's in TX and runs his entire homestead on solar.
If you're looking already looking at Bluetti power stations, why not the BLUETTI Solar Panel PV350, 350 Watt for Portable Power Station? I think Ecoflow has something very similar. However if you do want to build some bigger, and thus much more expensive, Eco-Worthy is having a sale and their 2 axis 6 panel tacking mount is very nice, and 42% off. :)
ReplyDeleteI'd go with joelsgulch. I bought his $5 ebook. He is a magnificent bastard.
ReplyDeleteI figure, if a hermit in a desert, who never brags about handyman skills or physical strength, can build a reliable system from nothing, so can I. Or at least, I can dream.
Someone mentioned sunelec.com
ReplyDeleteI second that. I have purchased panels twice from them for 20 to 30 cents per watt. They sell clearance stuff and some used panels as well as factory seconds. All of which are as good as new panels. Be carefull that they do have connectors on them as some of them get really good prices because they are missing
https://sunelec.com/ for some reason typing it in the way i did in my last post didn't work.
ReplyDeleteright now they have a bunch of panels for 38 to 40 cents a watt... just scroll down on the home page toward the bottom.
to give examples.. 655 watt panel for 235
410 watt panels for 155 dollars apiece and it looks like those are located in texas.VSUN VSUNN410-144BMH-DG.
there is another 400w panel for 144 in texas also. (NEW) HYPERION SOLAR 400W
not sure if near you but to be able to pick some up would save a lot of money.. shipping isn't cheap.
even a few years ago when I purchased 3000 watts of panels for 800 ish dollars. my shipping for the pallet of them was 300. still a stellar deal...
information on website is unclear as to full specs probably have to call them. These things go fairly fast in the past at these prices. however they always seem to have something most times I look.
ok i can't find that specific panel on vsuns website. However vsun is a Japanese company that is associated with fuji. The manufacture these panels in veitnam in a facility supposedly built to Japanese quality control standards.
ReplyDeleteMost of the panels on vsuns website are different wattage's but that have similar model numbers are claiming 21-22 percent efficiency, which compared to the stuff I bought a few years ago is simply outrageous. Its like giving an extra 20 30% capacity for free. Makes me tempted to buy a few more.
I would call sun electric and get specifications for those and then call vsun to verify them. It could be some weird lot vsun made with weird specs for some particular customer that just doesn't show up in their publicly listed products. however if it falls inside your rated voltage and amp usability range then this is a hell of a deal. Vsun gives a 15 year quality assurance warranty and a 30 year output warranty so I would consider their products pretty well made.
if you can drive to pick these up then your stated wattage would cost about 600 ish dollars? if you had to have them shipped I'm shure it would bump it to 1000 ish but that would still be a good deal.
Shipping companies really like delivering to loading docks. when I got mine I had to have them delivered 50 miles away and take a pickup truck they could load the panels into with a fork lift. That was for 26 panels though. For 4 panels at around 40 to 50lbs each.. they probably would deliver to you and just cut the packaging and hand them down one by one.. but you would need to verify that.
https://vsun-solar.com/sol_page/272.html
ReplyDeletebest I could find. exact model number showing in a installed project from vsuns website.
oh.. other unsolicited advice.. don't ever install on solar panels on the roof unless it is a fireproof roof. Just search for solar panel roof fires to see why :)
what your wanting to do is the way to go. For what your doing.. mounting them on a small bug out trailer for pulling behind your vehicle would be cool. You could move it around in the yard and if you had to leave home you could take your power centers, food, etc load in trailer and car and go. Though I doubt you have to deal with zoning for even mounting solar in the yard, having it on a trailer or moveable frame like you mentioned gets around that. Downside is they are much easier to steal on a trailer or frame :)
oh the craziness :)
https://www.santansolar.com/ I've used these people they have two locations one in Gilbert Az and one in Georgia. Used solar panels you might want to consider.
ReplyDeletePart 1 of 2
ReplyDeleteQuick brain dump... I'm near Houston, currently with 5 panels rated at 350 W each, and 10 kWh LiFePO4 battery bank. I keep a load on the system averaging about 125 W, so it uses 30% of charge daily. I feed the batteries from the grid at 50% and stop at 60%, so I always have at least 50% battery charge if power goes out. Two cloudy days in a row will trigger the grid charging, but I can live with that. I prefer to keep a load on the system so I know it's working and because batteries age to death almost as fast as they cycle to death.
It's easiest to compare batteries by Wh or kWh. Compare battery prices using $/kWh-cycles (lithium cycle life varies widely, from fancy 7000 cycles down to China special 1000-ish).
LiFePO4 is safest for the weight and cost, but you probably still want them away from your house. A battery fire, once started, will not be extinguished. I keep an area in a detached garage semi-air-conditioned and put the electronics and batteries in there, away from the house. That garage will be crazy expensive to replace with all its contents, but cheaper than the house and I wouldn't have to move away while rebuilding.
If you really plan to only charge portable battery packs, you'll probably want to match their input voltage to your battery bank. In addition to my 48 V main battery bank, I have a couple of portable battery packs that take 10-30 V input, so I use a cheap buck regulator module that can take the full input voltage range and charge them about half as fast they can tolerate.
Panels weigh a lot more than you planned.
Buy panels in bulk for best price (team up with a neighbor?). Buy more than you intend to use, initially because panels shipped freight will probably have at least one damaged and shipping a replacement is not economically feasible. Use the spare panel for another project (rain barrel pump, lighting, car/mower/etc battery maintenance), and save it in case one of the others breaks. Also buy more than you intend to use because you'll find more uses for the power, and you'll get less power than you planned for.
A panel rated at 350 W is about 1x2 meters (80"x40"), and gives about 300 W maximum (compare STC and NMOT specs). That will happen on a nice cool day (50-70°F). Hot days are noticeably less. Airflow around the panels will help.
MPPT charge controllers are happier with series panels than parallel -- one string of four panels is better than 2x2. My panels are 50 V open-circuit, and with some margin I can use five panels on a 300 V MPPT.
Ground each panel frame, and the rack if it's conductive, back to a ground rod close to your charge controller. Do this while you're putting the panels on the rack. Seriously.
Mount the panels on a cloudy day if possible. They get hot in the sun, and they get powered up in the sun.
Don't get too eager to plug everything in. Make sure everything's wired up properly before you turn on the disconnect switch. And do that in the morning when you can sit and watch the power rise for a few hours, to make sure everything is working properly.
Run all your wiring in expensive metal conduit. This is NEC Code, and when the squirrels chew up your cables, replacements cost more than the extra cost of the conduit. I'm not sure about portable racks -- I guess a sealed junction box will let you do that.
The rack weighs a lot more than you planned. And is flimsier than you thought. Wood can work, but leave room between panels because the wood will flex and you want them to flex individually, not as a breakable unit. Prime it, paint it, and inspect it frequently. Rust or rot on a rack will tear up your panels.
Start with your latitude as the tilt angle. Don't make tilt adjustable, it's too expensive and fragile. You won't get as much power in the summer as you'd like, so you may want to flatten the tilt angle a bit.
(cont'd)
Part 2 of 2
ReplyDeleteIf you want to use power all day, aim some of your panels a bit more to the east and some west. 20-30° will get you a few extra active hours of power on a clear sunny day, at the cost of peak power at noon. Two directions is all you'd ever need, morning power and evening power and average it at noon.
Rotating the panels during the day will make a lot more power than leaving them facing south. But it's not worth the time -- just buy more panels.
Instead of portable racks, you might consider adding some framework to let you screw in plywood "shutters" over the panels You can cover a 3 ft by 4 ft panel with two 3 ft x 2 ft pieces of plywood, in case the wind kicks up before you start putting the shutters on. This will also help the panels survive strong winds. Shutters will cost much less than portable racks, as long as you can plan for that. Don't let the panels flex, if you can help it. This means wind, temperature cycling, etc. That wears out panels.
Maintenance... do it. A lot of it. Learn how your system works, and you'll know when it's sick.
Cheap panels will develop snail tracks. Don't bother fixing it, just live with lower efficiency until you someday replace the panels.
Be able to reach your panels for cleaning. A long car wash brush with a hose attachment is useful, especially if it also has a soap reservoir. Or just use soap from a spray bottle on the stream setting and then start with the brush. Wet the panels, soap them, lightly brush them, and rinse them. You don't need a full RO water rinse, but avoiding excessive water spots will make you happier in the long run. A cloudy day is best so you don't temperature-shock the panels.
A combination charge controller and inverter will make life easier. If you only need 120 VAC, get that style. The larger ones can be combined in pairs for 240 VAC, but check the specs for current imbalance, or you'll find that even a small load will trip the breakers. For example, if the 120 VAC part draws 8 A (1 kW) and the 240 VAC draws 2 A (1/4 kW), that's enough to trip a one-phase inverter that's not designed for an unbalanced load. Bigger inverters can handle that, or you can just design around it. Like getting a 240 VAC inverter that's separate from the 120 VAC outputs (although properly grounded!).
Use the monitoring options on your charge controller and inverter(s), whether all-in-one or separate. Some have wi-fi, USB, or RS-485 connections. Feed the data into something you can view easily. Use an isolator if your monitoring system is not right next to your charge controller but is hardwired. Even 20 feet away is enough for ground spikes to zap a communications wire.
Solar companies charge "double" for panels used on grid-tied systems because each panel has a similar cost micro-inverter attached to it, and they all work together to create an AC waveform that can feed back to a transformer (-ish device) that syncs up with and feeds power back into the grid. This is much more efficient for a large array of panels, taking into account where shadows, dirty panels, etc, all affect the overall power output.
-- db