Help me make a hard solar decision

I am on the verge of installing a 6Kw solar array on my roof. I currently pay a very low rate (we are in an energy choice area of texas) of about 7.1c/Kwh. I was sold the system based on the concept of net metering, such that none of the solar power we generated would be wasted as the "meter would spin backwards" and we would only be charged by our power company for the net power used per the meter at the end of the month.

After HOA approval, lease company approval, months of paperwork, etc., the solar installer informs me that there is an issue with the power company I have as they will not offer "interconnection". Well that leads to actually looking at the detailed info from Oncor, who it turns out uses in-flow/out-flow metering.

Only a few of the REPs (Retail Electric Providers) buy back outflows, and of course their base rates are significantly higher than what I"m paying now, over 9c/Kwh and probably over 10c for the plans that will actually buy back.

Our usage the last few months has been 3700Kwh to 4700Kwh.

So now of course the installer says we are very unlikely to generate much in outflows anyway so it shouldn't matter.

But I'm really hesitant to go into this blind knowing that some amount of the solar we generate is going to be given away. The ROI on this system wasn't great to start out with (12-15 years on a 20 year lease) so there isn't much room for getting less value out of it.

Given my usage is it fair to say I should not worry about outflows? Or does the lack of net metering and the current great rate I'm paying blow this deal.

I'm thinking I should check the meter during the afternoon when the A/C is cycled off, none of our EV's are charging and if it is over 6Kw anyway, maybe he is right. Our smart meter was just installed so there is no online data to go by.

Thoughts?

at 7cents a kwh, it will be a long while before you break even here, but you knew that. I have an 8 kw system and on some days the outflow can be fairly large. Here's some data (sorry, I suck at formatting):

Date Time total energy produced(kWh) total energy consumed(kWh)
4/4/12 0:00 0 1.53
4/4/12 1:00 0 1.48
4/4/12 2:00 0 1.49
4/4/12 3:00 0 1.55
4/4/12 4:00 0 1.53
4/4/12 5:00 0 1.8
4/4/12 6:00 0 2.5
4/4/12 7:00 0.16 2.44
4/4/12 8:00 1.35 2.32
4/4/12 9:00 3.65 3.02
4/4/12 10:00 5.28 1.97
4/4/12 11:00 6.55 2.23
4/4/12 12:00 6.97 3.59
4/4/12 13:00 7.03 3.88
4/4/12 14:00 7.03 2.55
4/4/12 15:00 6.41 1.91
4/4/12 16:00 5.07 1.87
4/4/12 17:00 3.03 1.65
4/4/12 18:00 0.71 1.75
4/4/12 19:00 0.07 4.98
4/4/12 20:00 0 5.55
4/4/12 21:00 0 5.94
4/4/12 22:00 0 5.84
4/4/12 23:00 0 2.8

You will see that here there is a net inflow of 12.8 kwh, but there is 28 kwh flowing out to the grid with no compensation in your case, during peak daylight hours. I have real netmetering, and the rates are tiered (ie. you pay 11 cents for the first 13 kwh in a day tiering up to 33 cents for usage in excess of 23 kwh). So, it turns out, my breakeven is after 7 years. It gets even better when you get a EV in CA. Then you can get time of use metering ontop of netmetering and pay (in some tariffs) as little as 4 cents during the middle of the night when you are charging your car, and sell back energy at 33 cents during the middle of the day when the sun is generating power for you. That actually means that with an EV your fuel costs are negative! BTW, tariffs are changing here all of the time, so I may be a bit out of date. But you get the idea.

I like saving money, but I am convinced of two things: 1) its good for the country to be energy independent, and 2) global warming is real -- very real. Those are my two big motivations. So, if you can put up the money and be patient, then please do go solar!

Best,
Dave

Is that 4700 kWh a month? Without the Leaf we use about 4700 kWh in a year.

Most of your production is going to occur between 11-1 standard time. I'd check during that time. If your surplus is small during this time then it won't be much of a factor.

For solar to break even with the $.07/kWh in ten years you'd need to get to $1 per installed watt after incentives.

If you are doing it for environmental reasons, then maybe it's a good idea. But if I were in your situation I would rather pay a higher rate for wind power, since I know some parts of Texas have that option.

I have 15.3kW of solar, and I hate to dissuade you from going in that direction, but from a purely economic standpoint it may not be a great choice if you can't bank your excess generation. Your AC units and car-charging are the big draws. Everything else is negligible, unless you have a pool pump, and even then I would replace that with a variable-speed model.

Good luck with your decision.

ONCOR appears to offer a good rebate....Did you get this from ONCOR:

http://www.dsireusa.org/incentives/incentive.cfm?Incentive_Code=TX68F&re=0&ee=0" onclick="window.open(this.href);return false;

Edit: OOps. Looks like the incentive met its cap and is no longer available. Sorry.

druidz6 said:

I have an 8 kw system and on some days the outflow can be fairly large.
Best,
Dave

Click to expand...

Thanks for that table it is very helpful. What is your monthly kWh usage during the summer? I may be able to scale what you showed me to get a rough idea what I would be talking about.

jspearman said:

Everything else is negligible, unless you have a pool pump, and even then I would replace that with a variable-speed model.

Click to expand...

I do have a pool pump and replaced it with a variable speed model earlier this year. It says it draws about 400watts at the low speed it runs at that time of the day. I could make sure the Polaris runs at the peak hours to bump that up a bit though.

Hi Steve, my monthly output ranges from 600 kwh ( December) to 1500 kwh (July ) on average on a Sunpower system (36 230W panels) that is rated at peak output of 7.33 KW on the AC part of the inverter (I think its 8.28 kw DC). The shape of the curve in the table I included is typical, and is actual data for a reasonably sunny day. That was in the spring. You can get solar calculators on the web at a number of places. NREL provides one at http://www.nrel.gov/rredc/pvwatts/site_specific.html" onclick="window.open(this.href);return false; .

When and whether you get outflows will of course depend on your usage. I've got a lot of network equipment, irrigation pumps, pool pumps, etc. that account for a lot of use, beyond my Leaf. So Solar made a lot of sense. I just wish the price curve had come down in 2010 when I put my system in. Panel prices are much lower now! Still with the tiered electricity pricing, I will break even, not accounting for increased value of the house in 6 or 7 years.