ashdeacon
Posts: 12
Joined: Thu Sep 20, 2018 12:05 pm
Delivery Date: 02 Sep 2018
Leaf Number: 307779

Re: SolarEdge EV Charging Inverter

Mon Oct 15, 2018 12:53 pm

I am interested in sizing the system right.

I estimated I will do 20k miles per year in my EV. That equates to 5000 kwh approx. My current electric usage is 5500 kwh per year. Maybe I will charge my EV 80% at home vs out-and-about. So that would leave me with a 100% system at 9500 kwh or so.... I was thinking to target a system around 7500 kwh. Sound about right? I suppose the variable is the unknown amount I will charge at home.... but I suppose if I have solar my decision will be easy for most miles.

Valdemar
Posts: 2503
Joined: Tue May 10, 2011 10:32 pm
Delivery Date: 09 Sep 2011
Location: Oak Park, CA

Re: SolarEdge EV Charging Inverter

Mon Oct 15, 2018 2:11 pm

System size is expressed in kW DC - power, not kWh - energy. For starters you need to head to https://pvwatts.nrel.gov/, plug in your location + system orientation and see what size of system (kW) will produce the amount of energy (kWh) per year that you need. If you are in a NEM state and TOU is available to you under NEM you will want to further fine-tune the size, for which you need to understand the TOU rate structure of your utility and your usage patterns throughout the day, with EV added.
'11 SL, totaled
-1CB@33k/21mo, -2CB@53k/33mo, -3CB@68k/41mo, -4CB(41.5AHr)@79k/49mo, -5CB(38.85AHr)@87.5k/54mo
-0CB(66.14AHr)@87.5k/54mo (BBB), -1CB(53.92Ahr)@140k/29mo,
53.92AHr, SOH 84.5%, 140k miles

9kW Solar

Valdemar
Posts: 2503
Joined: Tue May 10, 2011 10:32 pm
Delivery Date: 09 Sep 2011
Location: Oak Park, CA

Re: SolarEdge EV Charging Inverter

Wed Oct 17, 2018 9:13 am

And just for reference, this how I ended up my last 12-month NEM period.

Image

What this means our system under-produced 4,156kWh against the total annual usage of about 19,000kWh (ouch!), yet we owe nothing to SCE. In fact, the final bill credit (-$189.63) indicates that I could get away even with a smaller system, under the current TOU rate structure anyway.
'11 SL, totaled
-1CB@33k/21mo, -2CB@53k/33mo, -3CB@68k/41mo, -4CB(41.5AHr)@79k/49mo, -5CB(38.85AHr)@87.5k/54mo
-0CB(66.14AHr)@87.5k/54mo (BBB), -1CB(53.92Ahr)@140k/29mo,
53.92AHr, SOH 84.5%, 140k miles

9kW Solar

ashdeacon
Posts: 12
Joined: Thu Sep 20, 2018 12:05 pm
Delivery Date: 02 Sep 2018
Leaf Number: 307779

Re: SolarEdge EV Charging Inverter

Thu Oct 18, 2018 1:13 pm

So under a TOU structure you get more credit for producing during a peak TOU time, just as you would pay more for electric used during the peak time.

I suppose generation of electric is never going to be at off-peak (usually at night).... so there will always be some net-gain due to the TOU structure.

Ashley.

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davewill
Posts: 4980
Joined: Thu Mar 17, 2011 6:04 pm
Location: San Diego, CA, US

Re: SolarEdge EV Charging Inverter

Thu Oct 18, 2018 1:34 pm

ashdeacon wrote:So under a TOU structure you get more credit for producing during a peak TOU time, just as you would pay more for electric used during the peak time.

I suppose generation of electric is never going to be at off-peak (usually at night).... so there will always be some net-gain due to the TOU structure.

Ashley.

Here in SDG&E land, Peak was moved to 4PM-9PM, so most of my generation time is now Off-Peak. Worse (from my POV) super off-peak now runs until 2PM on weekends, so much of my weekend generation is now at the lowest rate. Expect such changes everywhere as we go forward. I went from $0 per year to about $500 per year. I since moved to a different rate structure that has a monthly charge in exchange for a lower rate per kWh (but the same TOU periods) that should cut that down to $250/year.
2014 Rav4 EV, Blizzard Pearl White
2011 LEAF SL w/QC, Blue Ocean, returned at end of lease

Valdemar
Posts: 2503
Joined: Tue May 10, 2011 10:32 pm
Delivery Date: 09 Sep 2011
Location: Oak Park, CA

Re: SolarEdge EV Charging Inverter

Thu Oct 18, 2018 4:28 pm

Sooner or later battery storage will start making more financial sense than it does now.
'11 SL, totaled
-1CB@33k/21mo, -2CB@53k/33mo, -3CB@68k/41mo, -4CB(41.5AHr)@79k/49mo, -5CB(38.85AHr)@87.5k/54mo
-0CB(66.14AHr)@87.5k/54mo (BBB), -1CB(53.92Ahr)@140k/29mo,
53.92AHr, SOH 84.5%, 140k miles

9kW Solar

User avatar
RegGuheert
Posts: 6332
Joined: Mon Mar 19, 2012 4:12 am
Delivery Date: 16 Mar 2012
Leaf Number: 5926
Location: Northern VA

Re: SolarEdge EV Charging Inverter

Fri Oct 19, 2018 12:49 am

davewill wrote:Some people have changed their hot water and other big usages to electric to make a bigger system "pay", but natural gas is so cheap that it really doesn't.
But isn't the goal of many people to reduce fossil-fuel usage? It certainly is for me.

In any case, I suspect that the cost to operate a heat-pump water heater from solar is not too different than heating that water using natural gas, even including the additional cost of the equipment. This is particularly true if the homeowner is also running a dehumidifier and/or an air conditioner in the same area where the water heater lives (or could live).
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

User avatar
RegGuheert
Posts: 6332
Joined: Mon Mar 19, 2012 4:12 am
Delivery Date: 16 Mar 2012
Leaf Number: 5926
Location: Northern VA

Re: SolarEdge EV Charging Inverter

Fri Oct 19, 2018 12:53 am

Valdemar wrote:Sooner or later battery storage will start making more financial sense than it does now.
Agreed. Unfortunately, part of the reason that may/will become true in the future is that the utilities may/will eventually eliminate net metering.

That could be a justification for building a larger system today, even if some of the production benefits others for the near future.
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

User avatar
davewill
Posts: 4980
Joined: Thu Mar 17, 2011 6:04 pm
Location: San Diego, CA, US

Re: SolarEdge EV Charging Inverter

Fri Oct 19, 2018 9:27 am

RegGuheert wrote:
davewill wrote:Some people have changed their hot water and other big usages to electric to make a bigger system "pay", but natural gas is so cheap that it really doesn't.
But isn't the goal of many people to reduce fossil-fuel usage? It certainly is for me.

In any case, I suspect that the cost to operate a heat-pump water heater from solar is not too different than heating that water using natural gas, even including the additional cost of the equipment. This is particularly true if the homeowner is also running a dehumidifier and/or an air conditioner in the same area where the water heater lives (or could live).


Sure, there are reasons to do it, but I don't think anyone can pay for a bigger system and the new water heater with the savings.
2014 Rav4 EV, Blizzard Pearl White
2011 LEAF SL w/QC, Blue Ocean, returned at end of lease

User avatar
RegGuheert
Posts: 6332
Joined: Mon Mar 19, 2012 4:12 am
Delivery Date: 16 Mar 2012
Leaf Number: 5926
Location: Northern VA

Re: SolarEdge EV Charging Inverter

Fri Oct 19, 2018 1:57 pm

davewill wrote:Sure, there are reasons to do it, but I don't think anyone can pay for a bigger system and the new water heater with the savings.
You may be right. I don't know what natural gas water heating costs look like, so I can only do the comparison with an electric water heater. Perhaps someone else can give numbers for gas...

Given:
- Cost of a new resistive water heater: $400.00
- Electricity consumption of a resistive water heater: 4600 kWh/year
- Cost of a new heat-pump water heater: $900.00
- Electricity consumption of a heat-pump water heater: 1900 kWh/year
- Life of water heaters is assumed to be the same with no maintenance.
- Annual production of a 1-W PV module (on my house): 1.4 kWh/year
- Cost per kW of PV (installed): $3.00
- Cost of grid electricity: $0.12
- Cost of money: zero

Calculations:
- Initial outlay for resistive approach without solar: $400.00
- Annual outlay for resistive approach without solar: $550.00
- Initial outlay for heat-pump approach with solar: $900 + $3.00*(1900 kWh/year/1.4 kWh/year): $5000.00
- *Minimum* payback time using zero cost of money is: ($5000.00 - $400)/$550.00 = 8.4 years.

All of the above assumes that the price of electricity does not increase over time, but let's assume it is similar to the time value of money. (It's higher than MY TVM, that's for sure!)

Eight-and-a-half year payback is not a no-brainer, but it's a quite reasonable thing to do considering the photovoltaic equipment has a life of about 30 years or so.

So how much does it cost to run a natural gas water heater (50 gallons)? (FWIW, I just used the numbers from the sticker on the side of the water heaters for my calculations.)
RegGuheert
2011 Leaf SL Demo vehicle
10K mi. on 041413; 20K mi. (55.7Ah) on 080714; 30K mi. (52.0Ah) on 123015; 40K mi. (49.8Ah) on 020817; 50K mi. (47.2Ah) on 120717; 60K mi. (43.66Ah) on 091918.
Enphase Inverter Measured MTBF: M190, M215, M250, S280

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