PV Payback choose your Yardstick

nigtomdaw

Ive read many articles on PV payback and all seem to use different yardsticks to bring about different conclusions, my example is real world of mine and 2 neighbours who both live off grid.

Neighbour 1 Lives over a 1000 meters from grid lines across several owners lands and thus grid was not an affordable option, so he went for a 10 kva generator 4 kva inverter charger and 1000 am hour battery bank no re sources. Install cost 16000 euros . Running costs per year including his oil central heating 4000 euros (genny runs everyday to charge batteries automatically) owner pays little attention to energy conservation. RE investment zero

Neighbour 2 again no chance of grid connection has 900watts of solar 4 kva inverter charger 1000 ah battery, also uses oil central heating has good attention to energy efficiency and uses 2500 euros of diesel oil to run his home genset and heating. Also has a pool with pumping requirments which NB1 doesnt have. RE investment 4500 euros 900 watts of solar . 1000 watts for controller and wiring

So on 2 similar setups the energy consious guy with a small amout of solar uses 1500 euros of diesel less per annum will take about just under 4 years to recoup his solar investment over diesel genset only neighbour


Then there is I who had the option of grid power at 100 meters away at a one off cost of 6500 euros for a 5,5 kw supply. then I could start paying for the stuff and would still need backup as supply is unreliable. I choose to go down the solar wind front. I will leave out the inverter /battery costs as they are similar to neighbours one and two and the dead cost of 6500 euros to get a electricity supply would easily cover the cost on the inverter and a 1000 amp hour battery bank. I purchased 3.2 kw of solar at a cost of 13000 euros and 1500 euros for controllers and wiring total re investment (PV only)14500 euros. Since only installing 1.6 kw of solar panels at present time Im virtually energy *electric* free. The extra 1.6 kw array when fitted will cover the swimming pool pump use during the summer and extra generation for low winter sun hours so should still be almost electric free. I have estimated no more than 200 euros per year to run genset probably nearer 100. also I run a wood burner stove with back boiler for central heating wood costs 200 euros per year . but to be fair Ill round up my wood and diesel package to 500 euros to be generous That means as compared with neighbour 2 who spent 10,000 euros less on PVs but uses 2000 euros more on diesel it will take me 5 years for my PV payback investment. It goes without saying Im very energy efficient consious.

Compared to Neigbour one who uses 4000 euros a year against my 500 for fuel about a 4 years payback . Thats a simple comparison for my off grid neigbours.With fuel prices rising all the time but my costs now fixed I dare say you could easily knock a year off both payback times over this period. The sun doesnt do inflation or market forces . I,ve left out other variables which make the comparisons un fair but we all cook with gas and I use gas for my water heating as well as solar but my gas use is less that 100 euros a year and neighbours dont have solar water heating so this was left out of comparison. This was not a comparison against grid connection but a comparison againts no solar, not enough solar and just enough, figures are rounded up fairly to make comparsions easy, do not take to the definitive euro for accuracy, Nigel:p

Vic

Hi Nigel,

Well you have a nice large PV setup. Each person has a different yardstick. Some of us want to minimize our carbon impact, others are unable to make the initial investment ... the initial funds are just not available either directly or via a loan. In the US there are no real subsidies for off-grid systems, and often rural properties/projects are difficult to finance.

Stating the obvious, the time value of the money used to invest in a large solar system should really increase the payback times you mentioned.

My system is larger than really required because my yardstick is to try to avoid running a generator at all. Have never run the generator at all in the 20 months that the system has been on line. Usually, the batteries are discharged 3-4 % of capacity each day. This is considered "bad design" by most experts. This was my design goal by my yardstick.

Most of these tradeoffs are aesthetics. But think that our sticks are similar. Mine might be yards and yours meters, but similar objective ... minimize fossil fuel use.

A number of my nieghbors have little or no solar, but run generators for 3 or more hours per day. Primarily because it seems easier to come up with the funds for fuel every week rather than stepping up and dropping $20K- or 30 K to do a full off-grid solar/battery system. Also, here fuel has a cost ruoghly 1/2 of that in EU. One of these neighbors is in a deep canyon and really only gets 2 or hours of good sun, and then only in the summer. They have few alternatives.

Have fun with your silent system. Very little buzzing drone from your generator. Vic

nigtomdaw

Vic I welcome your comments, can I ask why you need 11 kw of Inverter power, I ony have 3.3 and apart from using a stick welder once without genset support que overload! rarley use more than 2/4 amps at 230 volts.I very rarely discharge more than 10 % on a sunny day even when using a electric cement mixer and 9 inch angle grinder (still building house) We dont have air con we use fans and window blinds , do you have heavy loads like welders saws milling machines that need this juice. On a night with lights on 2 TVs (lcd) Fridge freezer and even a washing machine going 2 laptops on internet we are rarley pulling more than 5 amps, but I see your not alone with big stacked high kw inverter set ups. I might be able to manage the day when my house is finished with all the trimmings and say should have bought a 5kw machine but cant think I would need 11 kw, your comments please;)
PS Ido get a mild grin when my neighbours tell me what they had just paid for a another 1000 ltrs of diesel to be delivered :roll:

Vic

Hi again, Nigel,

Good question on the stacked inverters. Couple of concerns, one is that when batteries age they seem to need a lotta current to EQ, so one main reason was thinking of that.

And as a Ham Radio kinna guy, there are times when one needs to run a power amplifier in order to communicate with distant stations. This often amounts to 2500 + watts from the line, so the reserve and easy 240 VAC split phase power is nice. Easier to do now than to retrofit later, and not a huge percentage increase in total system cost ... creeping featureism (is this a word ?).

This was my first real RE system, and it was hard for me to step up to spend the funds to make it happen -- recently added the extra 6X175 watt panels, but the original investment was a bit of a hurdle, but this stuff does generally not seem to become less expensive.

RE the fuel for generators, the neighbor in the canyon buys gasoline in town and hauls it out into the stix, this would get very old very quickly for me. Propane would seen a better choice, but think it is the investment thing again. We each get to choose.

Enjoy your pool, Nigel. A pool is something that I would love to have. Vic

nigtomdaw

I agree on systems set up cost it just gets more expensive as time goes by, but I can buy gear in USA ship to Uk pay taxes and still stack a 100 % markup and look good value, only down side on semiconductor ic gear is warranty, Ive just ordered 3 versions on delta lightning and surge arrestors and after import costs taxes ship to spain still will double my money. You re very lucky to live in USA with the prices you pay. I went on ebay USA the other day and bought 3 new C60 charge controllers byXantrex will shipto Uk then to Spain and double my total import price and sell for twice cost and still be 30% cheaper than competion, would you pay $300 for a bog standard C60 Ithink not.

What I didnt include in my original payback senario was genset servicing and breakdown costs I bought a relatively cheap chinese Kipor 4.5 kw diesel inverter genset serviced evey 100 hours and alternator failed at 500 hours i was lucky 2 find a guy in UK who swapped the alt for a british made unit 4 600 cigs , cigs are cheap in Spain as is liquor and Im still going strong , the chinese are catching up fast on re and I hope the USA keeps them in check, my C40s were made in china but one day soon minerals and base metals will soon dwindle and every damm thing will rocket,buy now buy wise and keep ur head down, my opinion is peak oil is just around the corner ! Ive just registered with this site been an Xantrex member and a Home Power Subscriber for a few years hence Xantrex gear , I like the helpful informal tone of this bullitin board, Nigel

SolarJohn

Re: PV Payback choose your Yardstick

I don't know why payback is such an important issue. Do you consider payback when you buy underwear, or a car? Those who choose to install a PV system usually do so because grid-supplied power is unavailable, unreliable, or expensive in their location. Some of us dabble with PV out of a genuine desire to reduce pollution and global warming. For most of this country grid-supplied electricity costs about 10 cents per kilowatt hour, a cost that makes a PV system hard to justify when considering cost alone.

John

BB.

Re: PV Payback choose your Yardstick

Yes, you guys are lucky to have $0.07 to $0.10 per kWhr for electricity in the middle of the country (and no tiers/unlimited use/flat rate pricing).

Out on the left and right coasts, we have our "governments" providing lots of regulations to "help" us...

Yes, vanilla plain power, costs me here $0.11-$0.12 per kWhr... But that is only if you use ~300 kWhrs per month or less... But, if you use more, it goes up quickly to $0.23/kWh if you use over 600 kWhrs per month (~600 kWhrs per month is average for my area if you don't have A/C and with natural gas service). Heavy use (like A/C) is over $0.36/kWhr.

And the Time of Use rate residential plan I have has a summer peak with a minimum/maximum pricing of $0.29 to $0.53 per kWhr... Yep--that is 1/2 a buck per kWhr. (lowest off-peak is about $0.09 per kWhr for this plan).

But--I am a cheap guy anyway--so I do get my usage in the lowest tier anyway (below 300 kWhrs/month)--but watch out when your government becomes more like California and starts to help you (and save the environment) with new regulations--high power rates, rolling blackouts and huge bond loads--that is why I went solar (my bill is about $5/month minimum connection fee), because I don't trust these guys.

-Bill

nigtomdaw

Re: PV Payback choose your Yardstick

Solar John Hi, it was just using a real life examples a different view of no solar a little solar and just enough solar to show in my opinion 4 years payback time against the guy with just a genny, I had the option for grid energy and choose to spend on going off grid, because
A. I was interested In Solar/ Wind Renewable Energy
B. 10 cents a KW even in USA is only going one way,
C. I had a capital windfall and rather that buy a flash new car or boat treat my self to my renewable enegy equipment .
D. Personally I think global warning is here to stay the next big problem is coping with its global effects and giant untility grids will be extremely vunerable to mother natures man made tantrums in the future !

I agree with you that apart from property, most peope when they make a substantial purchase of a car , boat, furniture never think of payback issues
But renewables do give a return on investment however long and I suspect payback questions will always come up for debate mine was just for fun !:roll:

SolarJohn

Re: PV Payback choose your Yardstick

Wow! I had no idea that so many people on the east and west coast are paying so much for electricity. I guess we'll all have to start looking at things differently in the future. If we'll willingly spend $20 to $30k for a car, I guess it will soon be common to spend that much for a PV or wind system. But as long as electric rates in Mid-America are only about 1% of our income, most people will conclude that it doesn't make economic sense to use alternatives, and a payback period of 20 years is not a strong incentive.

I'm glad that I've installed a small PV system, and enjoy updating it as my finances allow. And while I currently only save a few dollars a month on my electric bill, I suspect that will change. Plug-in-electric cars are likely to become popular in the future, due to the surge in gas prices. That alone will cause a strain on the grid, and might cause electric rates to soar. Just a thought.

John

BB.

Re: PV Payback choose your Yardstick

Think "we" have it bad--take a look at what people in old homes in the northeast (and other historic districts) have to put up with...

Wall Street Journal: An Inconvenient Turbine--

In neighborhoods across the country, there's a battle brewing: the environmentalists vs. the aesthetes.


As "green"-minded homeowners move to put in new energy-efficient windows, solar panels and light-reflecting roofs, they are bumping up against neighbors and local boards that object, saying the additions defy historic-district regulations, will look ugly or damage property values.
...
David Bannatyne was tired of the drafty, stubborn windows in his early 19th-century home in Concord, Mass., and was especially fed up with paying his $5,000 heating bill each winter.


But when he applied for permission to put in 17 new, energy-efficient windows last fall, the town's Historic Districts Commission denied his request, concerned that the windows wouldn't blend in with the home's historic character. After some debate, Mr. Bannatyne agreed to restore the windows instead. While he says they're now easier to open, he says his heating bills haven't changed. "I'm not doing the global warming issue any favors by keeping these windows," he says.

My hot water and heating bill (natural gas) is less than 1/10th that amount for an entire year (probably a smaller home, nicer weather, and I gutted the house and re-insulated, new windows, new heater, etc...).

Hmmm... Old Ford Model T's are fun cars--but government would not let anybody manufacture millions of them per year to put on the highway--or prevent people from dumping old cars and replacing them with modern transportation.

Old homes--there to look good for the other folks in the neighborhood... Heaven forbid that you try and do something to make them livable in the 21st century.

-Bill