Plan: Off grid solar with a Model S battery pack at the heart

[dalalsid]

I have. Dominion pays 15c per kWh, but it's taxable income. Makes the effective rate approximately 10.5c, depending on your income. Since dominion won't let you net meter and use the EV plan at the same time, your only choice is two meters. One measuring PV out to dominion, and a second meter coming in.

So I would end up generating and earning 10.5c, but paying dominion 11-17 for my use. The other option is to net meter on one meter, and use a dedicated meter for EV, but that means I can never offset my EV usage, which is at least half of my demand (2 EVs and soon 3).

Other states and utilities appear to let you combine programs on one meter. Charging at night is cheap, and during the day you receive credits at the prime rate - and it only becomes taxable if at the end of the year you still have credits.

I'm on the same dominion plan 15c/kWh. Since they issue 1099's I treat that as a power selling business and depreciate the panels. You get accelerated depreciation for being a green power producer and you can fully depreciate your panels in 5 years, the exact length of the dominion solar purchase contract. After 5 years switch over to net metering. So you get more than 15c/kWh thanks to the tax break.

P.S. I just happened onto this thread. Impressive system wk057!

 

[andrewket]

I'm on the same dominion plan 15c/kWh. Since they issue 1099's I treat that as a power selling business and depreciate the panels. You get accelerated depreciation for being a green power producer and you can fully depreciate your panels in 5 years, the exact length of the dominion solar purchase contract. After 5 years switch over to net metering. So you get more than 15c/kWh thanks to the tax break.

P.S. I just happened onto this thread. Impressive system wk057!

Well this is interesting. Thanks for the idea. Have you filed once already with this strategy?

 

[ZOMGVTEK]

That heat pump consumption is quite reasonable. It takes me ~15kWh a day to heat the upstairs to similar temps in similar conditions. When it's double digit negatives for days straight, thats closer to 30kWh. Thats without aux heat, so it drops a few degrees indoors while the unit defrosts and warms back up at those extreme low temps which kinda sucks. Doing this with resistive baseboard is in the 60-80kWh range on the coldest of days, and it runs the heaters near 100% duty cycle. So its kinda damn impressive a little 9000 BTU heat pump can do the job 30º below its rated operating range and still stay reasonably efficient. Although its hard to say what this does to its lifespan. Defrost cycles when its super cold outside sound brutal. Do you know if the defrost logic on your units appear to be time and temperature based, or something more advanced?

Are those steam humidifiers? The air handler consumption is quite a bit higher than I would imagine, and it sounds like yours can run without a call for heat? Steam is probably the way to go, I was curious how much those units would consume. My gas furnace takes easily under 2kWh a day worst case when heating, but its got low duct pressure in heat, an ECM blower, and a simple blow through humidifier. Kinda the best case, aside from an ECM draft inducer.

Personally, I wouldn't bother trying to get some air exchanger for the electrical room. The mini split should be happy enough cooling irrespective of outdoor temp. And, at least with my LG, the EER appears to be WAY above spec when cooling in very cold outdoor temps.

 

[scaesare]

Well this is interesting. Thanks for the idea. Have you filed once already with this strategy?

Interesting indeed...

 

[dalalsid]

Well this is interesting. Thanks for the idea. Have you filed once already with this strategy?

Yes, last year. I was also thinking about the roof etc. for depreciation but figured that would get too complicated and just depreciated the solar system.

 

[wk057]

It's 3:30PM. I just found out that the storm that came through a little before noon knocked out power in this whole area... Off-grid FTW.

Here's a video clip of the storm that came through. Nice dime sized hail too. 65 MPH winds. Tornado warning. Was pretty bad.

2016-02-24 - Hickory, NC - Tornado Warning! (Got some hail instead) - YouTube

Here's Duke Energy's outage map right now (basically something wrong in every part of their territory):

 

[RubberToe]

WK,
Good test of your system. How much power do you have stored, and what is your "hunkering down" usage per day?

RT

 

[wk057]

Good test of your system. How much power do you have stored, and what is your "hunkering down" usage per day?

Depends on the weather. Right now it's ~65F outside. I need basically zero HVAC. Cars are also charged to roughly normal usage charge, so, that's fine for a bit too.

It's sunny, and batteries are holding about 140 kWh. Assuming my panels give me a minimum amount of power each day, that's 3 days of normal no-changes usage. If I know it's going to be rainy and nasty for a bunch of days I can cut consumption in half pretty easily (and have) which can stretch things to about a week of bad weather.

Fortunately the forecast is for sunny skies for at least the next few days, so I'll probably end up wasting power. No worries here. Coal grid can stay down a while longer and we can all breathe a little better.

 

[freds]

I know this is heresy; but why not let the wife drive the P85D on say Tuesdays and Thursdays?

 

[wk057]

I know this is heresy; but why not let the wife drive the P85D on say Tuesdays and Thursdays?

Blasphemy!

Actually, she prefers her car, believe it or not.

 

[nwdiver]

WK, your fellow North Carolinians have been busy....

 

[nativewolf]

WK, your fellow North Carolinians have been busy....

View attachment 112751

Well isn't that odd. I was wondering about all the solar I was seeing in the middle of nowhere, this isn't rooftop solar it is 10 acre fields full of solar panels, not the 1000 acre projects in CA just 10 acres here and there. Must be Duke getting govt $ somehow

 

[TheTalkingMule]

I believe NC has a 35% state tax credit on top of the 30% federal ITC. These guys are essentially printing money.

 

[pgiralt]

I believe NC has a 35% state tax credit on top of the 30% federal ITC. These guys are essentially printing money.

Had :-(. The state legislature did not renew the credit so there was a mad scramble at the end of the year to get solar installed. If the goal of the incentive was to promote solar in the state, it clearly worked. Too bad it didn't get extended.

 

[Tedkidd]

That heat pump consumption is quite reasonable. It takes me ~15kWh a day to heat the upstairs to similar temps in similar conditions. When it's double digit negatives for days straight, thats closer to 30kWh. Thats without aux heat, so it drops a few degrees indoors while the unit defrosts and warms back up at those extreme low temps which kinda sucks. Doing this with resistive baseboard is in the 60-80kWh range on the coldest of days, and it runs the heaters near 100% duty cycle. So its kinda damn impressive a little 9000 BTU heat pump can do the job 30º below its rated operating range and still stay reasonably efficient. Although its hard to say what this does to its lifespan. Defrost cycles when its super cold outside sound brutal. Do you know if the defrost logic on your units appear to be time and temperature based, or something more advanced?

^^^^

Good points. There may be lots of continuous commissioning tricks on your heat pumps, I know there are on the Carrier Greenspeed. Timed defrost is not the setting you want.

Also might wanna see if defrost without resistance is a comfort penalty (if the wife notices, turn it back on). This can cut heating use in half.

 

[dhanson865]

WK, your fellow North Carolinians have been busy....

It embarrasses me that my state (TN) gets better sun than half the country and has near zero development. Compared to NC we get about the same solar insolation but we have way less solar installed.

 

[wk057]

It embarrasses me that my state (TN) gets better sun than half the country and has near zero development. Compared to NC we get about the same solar insolation but we have way less solar installed.

I think Tennessee has one of the largest residential solar systems in the country somewhere... forget where I read that.

A friend of mine believes I have the second largest residential off-grid system in the country, and top-10 residential systems period. Would love to actually find some data to support that (or not).

 

[Ampster]

It embarrasses me that my state (TN) gets better sun than half the country and has near zero development. Compared to NC we get about the same solar insolation but we have way less solar installed.

I hope WK057 finds the data to support his view that you have more. Fear not, we are at a point that the economics are compelling. There are still some political hurdles, but in the long run the trends are encouraging.

 

[EcoHeliGuy]

I hope WK057 finds the data to support his view that you have more. Fear not, we are at a point that the economics are compelling. There are still some political hurdles, but in the long run the trends are encouraging.

Seen the price of installing a power poll on your own property lately? That pretty much covers a solar install.

 

[Ampster]

Seen the price of installing a power poll on your own property lately? That pretty much covers a solar install.

Can you clarify? In my development our utilities are underground. Maybe your point was that if one were to install a combined solar/battery behind the meter, you could avoid the cost of a new power pole.
In the Central Valley of California I have seen farmers install solar plus batteries to run well pumps, because that was cheaper than having the local utility string wires and install a meter.