Solar System Size Based on Budget

[K1ng0011]

I live in the PNW in Washington state. I live in an area with cheap electricity. I am trying to figure out what sized solar system I can reasonably expect based on my budget. Determining the cost of the the inverter/battery is fairly straight forward. However all of the other components, panels, microinverters/optimizers, solar rails/mounts, and other misc. items I am having trouble getting accurate pricing. There are lots of vendors of the different components and I having trouble determining what is realistic for new equipment to qualify for the tax credit. Ideally I would like to get as close to 15kwh as possible based on all of the information I have collected. I am looking to get backup power for my house in the short term outages we have and reduce my electric bill. I may also buy used panels out of pocket later to increase the size of the system if I am not able to get close to the 15kwh with the current budget if it is not reasonable.

Budget: $23,000 - 30% Rebate = $16,000
https://www.bankrate.com/loans/loan-calculator/ - $16k = $148/month = 15 years
https://pvwatts.nrel.gov/pvwatts.php (15kwh Array) - 14,739 kWh/Year
https://sunroof.withgoogle.com/ - 1068 hours of usable sunlight
Electricity Cost - .10279
Average Electricity Usage KWH - 1072kwh
Average Monthly Bill - $154
Time of Use - N/A
Ground or Roof Mount: Roof Detached Garage
Roof Direction: East/West
Garage Size: 30x30
Distance from Garage to House: 50ft
Roof Material - Metal

Hybrid Inverter: SOL-ARK 15k
Battery: https://signaturesolar.com/eg4-powerpro-14kwh-all-weather-lithium-solar-battery-wallmount/


From My Electric Company: The net metering reserve allows you to roll over credit from net metering to apply to energy charges in another bill period. Per state law, net metering reserve credit expires on March 31 of each year.

 

[ksmithaz1]

Once the bug bites, the depth of the desire is deeper than the checkbook.

The EG4 18kpv/12lv is less expensive and a less mature product than the Sol-Ark. Rumors have a newer firmware which may close the gap some more, I like mine. It will be prettier paired with the selected batteries.

The Sol-Ark is a 12000 watt output device same as the EG4 (240V/50A split phase). It is doubtful you will push 15K of PV into either, but the EG4 is rated marginally higher accepting up to 18KW of panels.

On the battery front bang for the buck, straight rackmounts beat the wallmounts, Pure DIY beats rackmounts, and the installation is uglier as the bang gets better.

You are likely going to want more than 14KWH of battery once the bug bites. Panels keep getting cheaper, look for something < 0.25/watt, it's out there by the pallet not infrequently, your going to need to figure out how many panels you can fit and where. Note the physical dimensions of the panels you get, they are all different.

At the price you are paying your ROI will be awful.

You will probably want about 10KW of panels and 30K of batteries. It gets complicated if you grid tie, you going to toss significant money getting all that in place. That 10/30 ratio will scale up double, after which you are going to want more battery before more panels, depending on if you have an EV or something.

You really should figure your estimated highest demand you want to provide for.

 

[glandpuck]

Question: You said your electric bill is $1,848 and you use about 14,739 kW annually. This figures out $0.1254 per kWh. Solar will not save you any money. The only benefit you receive from solar is production of clean electricity which others including the utility are doing on your behalf.

If you want to stabilize your electrical connection in emergency needs, you would benefit much more from a standby generator or could even go to a primary. They will cost less and provide peace of mind. If your water tanks or heating are gas, then you would be better off to install heat pumps for heat and water.

This is my opinion. It's free.

 

[Danke]

The Sol-Ark is a 12000 watt output device same as the EG4 (240V/50A split phase). It is doubtful you will push 15K of PV into either, but the EG4 is rated marginally higher accepting up to 18KW of panels.

Seems every inverter spec sheet I read publishes numbers different ways.

Sol-Ark claims 15k with both battery and PV, 12k with battery only. Some here have posted results higher than 15k with just PV.

EG4 says 18kW PV usable, max 21kW . Sol-Ark says 19.5kW allowed.

EG4- MPPT 25/15/15A, Sol-Ark- 26/26/26A (self limiting)

The Deye inverters seems to have better specs than the Sol-Arks in same class, like the 8k and 12k. Outside of not having 200A pass through, the Deye 12k is more similar to the Sol-Ark 15k.

 

[Rednecktek]

Just to ruin your day, if you're going to be doing a grid tie system, EVERYTHING has to be all UL listed and certified and inspected which makes things WAY more expensive because we're NEC2020, aka "Screw The DIY Crowd" rules. We're right up there with California in hoops to be jumped through.

Also, unless you're on the East side of the mountains or that one part of Whidby Island, your solar production is going to have a hard time breaking even within the warranty time of your system. I used to have a place in Monroe and every time I did the math it came up between 38 and 41 years to break even on the cost of the largest system I could fit on there due to lousy weather.

Also, do all your math without the tax write-off because you still have to pay up front and ask the IRS for some of the money back as credit towards your tax debt over the next few years.

If you want to do it because it's cool and fun, or you want to do it because power outages suck, then it's awesome! If you're doing it to save money on your power bill, then you'll be disappointed.

 

[ksmithaz1]

Seems every inverter spec sheet I read publishes numbers different ways.

Sol-Ark claims 15k with both battery and PV, 12k with battery only. Some here have posted results higher than 15k with just PV.

EG4 says 18kW PV usable, max 21kW . Sol-Ark says 19.5kW allowed.

EG4- MPPT 25/15/15A, Sol-Ark- 26/26/26A (self limiting)

The Deye inverters seems to have better specs than the Sol-Arks in same class, like the 8k and 12k. Outside of not having 200A pass through, the Deye 12k is more similar to the Sol-Ark 15k.

There is a you tube video on the EG4, the guy runs it up well over 60A before it cuts off. Good to know you may can if something is amiss.

I stand by they are both 240v/50a units, and you don't ever want either to be running over that level for any significant period of time. (more than an hour or three). Most high demand loads are fairly short-lived. The things that get you are like EV charging, or My HVAC here in the summer. Even the oven/range, is surprisingly low. Yea it spikes on high while you boil the water then you turn it off in 10 minutes when the pasta is soft. It spikes pre-heating the oven, then cycles to maintain the temp. If I have 5K of peak demand I want a 8K or better unit. You can tighten the gap as overall peak goes up, since you should not need extra headroom. I have 24KW, I did hit it very briefly once, but I'm rarely over 15. 60% is a good 95th percentile target for me, but if I were not trying to go 100% 24x7, I could tone it down. If they get redundancy fixed, I can pay attention to my loads and do a firmware upgrade or other maintenance to one unit without jumping on the grid. That will be nice

 

[K1ng0011]

Question: You said your electric bill is $1,848 and you use about 14,739 kW annually. This figures out $0.1254 per kWh. Solar will not save you any money. The only benefit you receive from solar is production of clean electricity which others including the utility are doing on your behalf.

If you want to stabilize your electrical connection in emergency needs, you would benefit much more from a standby generator or could even go to a primary. They will cost less and provide peace of mind. If your water tanks or heating are gas, then you would be better off to install heat pumps for heat and water.

This is my opinion. It's free.

Currently the only utility I have from the city is electricity. Natural gas is in the street but not to my house. All appliances are all electric. Heat is electric baseboard. I have a 100amp electrical panel. My house is small 1100sqft. I just replaced my electric water heater with a new one. My electric water heater is in a weird little bump out on my house that they added and does not have enough space for a heat pump water heater. I will likely be adding quite a few additional electric loads on my property in the future. The problem I have with full time standby generators is that they may cost less than a solar system but they don't pay for themselves over time. Will all/some of your solar components last the full amount of time to pay themselves who knows? However at least there is a chance they will pay themselves off and you might get money back in your pocket in the long term. Our power outages typically do not last long enough for justification of a full time standby generator. I have thought about it some and wondered if I should just get something like a SolArk 15k and a EG4 PowerPro and just use the battery like a standby generator and not have solar panels at all. I believe the SolArk can charge batteries connected to it from the grid.

Once the bug bites, the depth of the desire is deeper than the checkbook.

The EG4 18kpv/12lv is less expensive and a less mature product than the Sol-Ark. Rumors have a newer firmware which may close the gap some more, I like mine. It will be prettier paired with the selected batteries.

The Sol-Ark is a 12000 watt output device same as the EG4 (240V/50A split phase). It is doubtful you will push 15K of PV into either, but the EG4 is rated marginally higher accepting up to 18KW of panels.

On the battery front bang for the buck, straight rackmounts beat the wallmounts, Pure DIY beats rackmounts, and the installation is uglier as the bang gets better.

You are likely going to want more than 14KWH of battery once the bug bites. Panels keep getting cheaper, look for something < 0.25/watt, it's out there by the pallet not infrequently, your going to need to figure out how many panels you can fit and where. Note the physical dimensions of the panels you get, they are all different.

At the price you are paying your ROI will be awful.

You will probably want about 10KW of panels and 30K of batteries. It gets complicated if you grid tie, you going to toss significant money getting all that in place. That 10/30 ratio will scale up double, after which you are going to want more battery before more panels, depending on if you have an EV or something.

You really should figure your estimated highest demand you want to provide for.

The demand is primarily to get through a few hours of an outage. I think a 15kwh battery would be enough for that. Our outages typically last a few hours 4-10 hours. I am on a shallow well and would like to be able to flush my toilet. The solar would help to offset some of the cost of the additional electric load I may have in the future. Unlike most people I have a mostly free 42U 4 post network rack in my house rated for 1300lbs so I can also do rack mount batteries I would just rather have it wall mount outside if possible. My garage has its own electrical panel and meter. I dont plan on backing up anything in there. I dont have an EV but I am considering one primarily due to the miles I drive a month. I am looking at the solark due to the better support. If something was sitting on my wall for ten years I would want to have good support on it. I have read some of the forum posts on here about the EG418k and SS and its something I want to stay clear of even if it costs less.

Just to ruin your day, if you're going to be doing a grid tie system, EVERYTHING has to be all UL listed and certified and inspected which makes things WAY more expensive because we're NEC2020, aka "Screw The DIY Crowd" rules. We're right up there with California in hoops to be jumped through.

Also, unless you're on the East side of the mountains or that one part of Whidby Island, your solar production is going to have a hard time breaking even within the warranty time of your system. I used to have a place in Monroe and every time I did the math it came up between 38 and 41 years to break even on the cost of the largest system I could fit on there due to lousy weather.

Also, do all your math without the tax write-off because you still have to pay up front and ask the IRS for some of the money back as credit towards your tax debt over the next few years.

If you want to do it because it's cool and fun, or you want to do it because power outages suck, then it's awesome! If you're doing it to save money on your power bill, then you'll be disappointed.

I am not familiar with the NEC2020 rules. When you say everything has to be UL listed and that will make things more expensive. Do you mean that you will have to buy products like microinverters from enphase and not from a smaller manufacture? Is there a UL listed solar kit that you can buy to get a sense of what the cost might be?

 

[chrisski]

Is there a UL listed solar kit that you can buy to get a sense of what the cost might be?

Not really. Each case is so specialized that it will be customized to your house. I haven't seen a kit that has everything for a UL listing like cutoffs and Arc Faults. I just had a Factory built UL approved Inverter/charger and 2 X Charge Controller fail inspection by the town, and work needed to be done on that UL approved piece of equipment.

I think as hard as getting UL components is, getting plans drawn up and approved and inspections is much harder. On top of UL approved, the local AHJ at the inspection and permitting has final say. Each town can be different. In an adjacent town, the town did not give operating permission for a UL approved 20 kWh battery pack.

I dont have an EV but I am considering one primarily due to the miles I drive a month.

I bought an EV to replace a paid off car and probably save $200 a month on gas. At least that's the part of the truth I tell them. I used to tell them I took on a payment several times that. I used to tell them about my payment, but they wither didn't hear that or were not interested in the payment portion, only the gas savings.

I am not familiar with the NEC2020 rules.

Take time and look at this if you want to DIY. For me, this would have taken years to research, permit, install, and inspect my system. That's why I went with a contractor. THis also changes every few years. There is a NEC 2023 code that has not yet been adopted that when it does, there will be changes.

 

[scrubjaysnest]

I have a quote for a 50 to 60 amp off grid system installed for $40k. That is enough for 800sq ft home with most appliances on propane. That is the up front cost before the 30% is taken out at tax time.

 

[Whats-n-Watts]

You probably won't see a RIO until you're panels need replacement and likely many batteries.
My power bill is a whopping $120 per month yearly average. About 6 months out of the year we use 600kw per month or less. It has been as low as 510kw so needless to say Im not going to save any money for about 6 years if that.
Good thing that isn't the reason I am going off-grid. It's not about the money at all. I make enough of that that I don't even notice our tiny bill each month. It's about the governments ability to shut this country off whenever they get ready to do so. Don't think they can't or won't.
As several mentioned to grid ties both your building inspector as well as the power companies engineer must approve and pass your system before you even turn it on. You may or may not have the ability to build the system that requires. I'm hear learning too and from what I have learned is it's far more complicated than most realize and are capable of pulling off. As someone else said panel size matters.
I built or house 24x24 open floor plan. You can see the shower from the front and only entrance door.
I pay as I go. I've been debt free 2 times in my life. 8 years now on my second round and chance at financial freedom and sure am not going in debt over a small light bill so wwhat I am doing is targeting essential demands and building small individual systems for that one job as I go. The house isn't grid tied but I do have grid power on the property connected to our double wide modular home that is way larger than we need since all the children are grown and gone.
I'm doing individual inverters as well as banks. Some my think I am backing up but they aren't paying for my system or maintenance on it as required. I'm thinking down the road. For example your big ole all in one 8kw plus expensive unit takes a dunk just after the warranty runs out? You have that expensive thing to buy all over again. Maybe it was just the charge controller built in or in the same token the inverter it's self and the rest in fine? No thanks. Having said that it's very hard to find pv at .26 cents per watt unless you buy a pallet. Which I can do but it will take time to recover enough to buy the rest. ALL the components and batteries. Not smart to me if that's going to take over 6 months.
Solar I have learned is in 3rds or at least in my shopping when you look at it in terms of money. 1/3 cost will be PV, 1/3 on battery bank and 1/3 on inverter, cables, switches, breakers combiners and last but not least mounting. Of course those can be manipulated in either direction but that's about the size of it imo.
Example I am powering a shed with a small mini refrigerator and 2 freezers. A small chest and medium upright.
Last counts I heard was the sun isn't going to burn out until after I am dead so a massive bank of batteries doesn't fit me too well in the thought that PV last up to 25 years. Most Batteries 6000 days at best and that's only if you stroke them properly.
The 3 appliances use a total of 2,340kwh in 24hours. Will all 3 running the total watts is 202 watts. System in simple is
1,200 watts of PV
One charge controller
One 2,500 watt inverter
And a 12v300ah battery

Solar being calculated by the kwh demand over a 24hr period and divide by 4. In my case let's round. I like round figures. 2400wh/4rs = 600watts of PV.
As you see above the amount I have is double. Yesterday it was heavy overcast here. I got a panel out and measured output at about 45 degrees facing the sun. My meter read 56 watts. I had my wife stand directly in front of the panel to ensure an even more heavy cloud condition. It still put out 50 watts.
Having said that when the sun is shining on the location of the pv it receives full sun even in winter from 9 a.m. until about 3 right now. Summer is almost daylight to dark. So even let's say a heavy cloud day like yesterday. Zero sun and my 100w panel is putting out that 50w. 600w*4hr = 2400w.
I could have gotten away with a much smaller battery since the maximum recording of kwh measured during no solar activity being just 610whr.
In short what I paid in extra pv enables me to use a bank much smaller due to not worrying about low solar days. And sufficient battery should it fall short a day or two which I don't see happening. That brings me to an issue to consider which is climate. Here about 4 months, winter time, are the main months we have any substantial cloud cover lasting more than a day. At the most 3 days of it typically speaking. The 2,340wh recording was done during summer in the heat of it. They are using much less per day and not even enough to mention at 60wh for the mini fridge over night due to the colder temperatures as they are in a uninsulated shed. Nothing runs at 27 degrees except the heat lol
I have $50 in each pv, $50 in a charge controller and $251 in an inverter and the battery was $500. Cables and whatnot I haven't totalled yet.
You maybe thinking that the 2500 watt inverter for a 202w load is way too much. The entire load from all 3 at measured peak is just under 1,000 watts. Still a 2500 watt continuous is overkill? Nope. I have a friend with an electric component business and was talking with him about the inverter sizing and he said to throw the peak rating out the window. It means nothing more than shutdown. He also said Inverter fans in an more in than off state was caused by either too small of an inverter, too small of cables/battery or thermal switch for the fan has failed but it's usually because people undersize. He told me unless I want the fan sucking my battery dry to multiply your max continuous expected load by 3 but no less than 2.
Back to what else matters. Your budget and ability to handle future failures within your budget. Future is hard to predict so I figure I can afford to keep a $251 dollar back up on hand a whole lot easier than I can swing a $2000 or more AIO unit that handles all my loads.
My kitchen gets its own system, water heater, all other outlets and lights get their own system. Heat and air gets its own system. Each system will have its individual bank as well as inverter. The heat and air will be the biggest system. Even my refrigerator gets its own.
You see I broke them down to to the best of my ability after a 2 plus month long power audit. I saw that I could make clone systems for 2 pairs of systems meaning I can keep less backups on hand. Same volts, same inverter and same brand and watts PV etc. 2 back ups for 4 systems. I gave it diced up to one battery per system 3 days worth at 100% discharge. Won't ever happen. I have grid power and a charger and an 8.5kw generator. I have very little in this shed system but the pv cost what it cost when you get a little at the time. This probably wouldn't work for you but the topic was budget solar and this is how I'm doing it on a budget. Again I figured they are small systems with gobs of power for the load on a sunny day and I've covered them clouds allowing me not to spend on bank. 25 years pv and not worry about cloudy days or 5 to 8 years on batteries ?

 

[Hedges]

Currently the only utility I have from the city is electricity. Natural gas is in the street but not to my house. All appliances are all electric. Heat is electric baseboard.

Pay for gas hookup, before it becomes illegal. Even if it costs several $thousand.
In my area, electric (resistance) heat is about 8x the cost of gas heat. Your electric is several times cheaper, don't know if your gas also is. We are no longer allowed gas hookups for new construction.

The demand is primarily to get through a few hours of an outage. I think a 15kwh battery would be enough for that. Our outages typically last a few hours 4-10 hours.

Occasional outages, AGM is simple and has 10 year lifespan (if premium quality). You can use an inverter/charger or hybrid as UPS, automatic or manual transfer.

PV panels are cheap, you can buy some and put in yard or elsewhere to make it last longer.

Do you really need 12kW or so to be comfortable during an outage? Smaller battery might be enough, so long as you're not using it for heat (see natural gas, above), maybe just air handler.

I am on a shallow well and would like to be able to flush my toilet.

Fill an above-ground tank with grid powered pump. Use a 12V battery and SurFlo pump to supply the house, check valve and parallel plumbing to your main system.

The solar would help to offset some of the cost of the additional electric load I may have in the future.

Works best with an inverter that blends its AC with the grid. Technically, should have utility permission.
Get a name-brand UL listed inverter that does zero-export to CT attached by meter.

An off-grid inverter like used for an RV may be simpler and cheaper, but it won't make use of PV while grid connected.

I am not familiar with the NEC2020 rules. When you say everything has to be UL listed and that will make things more expensive. Do you mean that you will have to buy products like microinverters from enphase and not from a smaller manufacture? Is there a UL listed solar kit that you can buy to get a sense of what the cost might be?

There are some imports with UL listing.
We have heard from SS that although they had a UL listing certificate, equipment was shipped without stickers attached. Worked for some AHJ, not or others.

Don't go with Enphase for your backup system. Get an inverter that works with 48V LiFePO4 and AGM batteries - many economical choices (although UL listing for ESS requires inverter and LiFePO4 tested together.) There are several brands. Or for a higher price and more limited selection, some use HV batteries. I plan to install SMA SBSE, maybe add ABU and BYD 400V battery later.

 

[K1ng0011]

I am really not sure at this point where I should look for solar panels like what website to look at pricing or what would be a good price for a 5kwh, 10kwh, 15kwh system. If I cannot make solar make sense financially I wonder if it would make sense to do a hybrid inverter/battery with no solar vs a full standby generator. It may be something I have to revisit in a few years after prices on products come down.

 

[Whats-n-Watts]

I am really not sure at this point where I should look for solar panels like what website to look at pricing or what would be a good price for a 5kwh, 10kwh, 15kwh system. If I cannot make solar make sense financially I wonder if it would make sense to do a hybrid inverter/battery with no solar vs a full standby generator. It may be something I have to revisit in a few years after prices on products come down.

If you're only concern is back up power when the grid is down your better off getting a generac by far.