Planning to reduce electric bill by solar push, no feed back to grid. Daylight hours only.

[roadrunner]

I bought a used trailer after I got tired of apartment living so I could save up for a house. Lot rent was cheap but electricity in the summer was outrageous. My current house is twice the square footage of that trailer and the trailer easily used twice as much electricity as my house. In August the A/C could run for hours without shutting off. You could feel the heat radiating from the ceiling. A lot of folks here used to build a roof over the trailer to cut the solar gain on the roof and it helps a lot, but you can't do that in a park.

New models are built with shingle roofs and some insulation, not like the tin can I had.

exactly, mine is an older 14x 60, you know what there like, and living in a park, and by az laws, since they have an axle under them they are goverened by motor vehicle, and the same laws that pertain to home renters dont apply to us, thats why there so many trailer for rent, the landlords can get away with lots of stuff, for instance i have no heater in here but a plug in electric one, it uses the ptc technology, so it doesn't cost anything to use, and that's in the living room combo, and we have a little quartz one in our bedroom.

 

[roadrunner]

Grid tie inverters need to sense power from the grid in order to operate. If you disconnect the grid power, the inverter faults and stops producing power.

exactly, thats why you cant backfeed when a grid tie inverter shuts off, so theres no danger to the lineman

 

[roadrunner]

Good point. Not sure whether it is an option given regulations/constraints, but putting $400 into better insulation may well be wiser investment than putting that same amount into solar...

cant put in better insulation in a trailer without tearing it apart and basiclly starting over,including the roof, theres no access except to remove the roof, and i rent, my landlord wont do anything for anybody unless a law tells him he has to and laws for mobile homes are way more laxed than for a rental house.

 

[roadrunner]

I think what i am going to do is my original plan and see how it works by trial and error, and maybe build a battery backup and ill watch wills video again i posted, and look into a different inverter, the one he used in the video with his link says $300, but when i clicked on the link it said $399, so i will check again, but in his video, he shows a Battle born battery of 100 ah, and a simple connection to the grid and home and says it wont back feed. so this could be an emergency backup, and go with my first post for my swamp cooler and just have me switch it on and off with a power strip

 

[fafrd]

cant put in better insulation in a trailer without tearing it apart and basiclly starting over,including the roof, theres no access except to remove the roof, and i rent, my landlord wont do anything for anybody unless a law tells him he has to and laws for mobile homes are way more laxed than for a rental house.

Understand. So you have a shed or something where you think you can hide two solar panels and where will you mount the GTIL inverter (and battery and SCC if you decide you need to go after some nighttime consumption)?

 

[fafrd]

I think what i am going to do is my original plan and see how it works by trial and error, and maybe build a battery backup and ill watch wills video again i posted, and look into a different inverter, the one he used in the video with his link says $300, but when i clicked on the link it said $399, so i will check again, but in his video, he shows a Battle born battery of 100 ah, and a simple connection to the grid and home and says it wont back feed. so this could be an emergency backup, and go with my first post for my swamp cooler and just have me switch it on and off with a power strip

Well first, you don’t need an AC charger, that’s not going to buy you anything (but misery).

You need a Solar-powered inverter, either stand-alone if you just want to power some 240V appliances during the day, or grid-tie inverter limited (GTIL) if you want your appliances off of grid power when the solar can’t provide enough power.

If you decide to add a battery, either your all-in-one needs an MPPT solar charge controller (SCC) or you also need to add a separate SCC.

The key thing you need to figure out is how much power you can expect from your two panels. Suggest you check out PV Watts: https://pvwatts.nrel.gov/

Enter your zip code, solar array size, azimuth angle and tilt and it will estimate how much power you can expect by month (or even by day or hour if you download the data).

With that alone and the estimated consumption of your largest daytime consumers (cooler and fridge), you can estimate how many kWh you can reduce by month or day.

If you are able to consume everything your solar array is generating as it is generating it (meaning during the day only), that is the best you can do.

If your array will be generating more power than you can consume as it is being generated during the day, you need to add a battery (as well as a solar charge controller if your all-in-one box doesn’t already have one).

Charging a battery from grid power won’t help your situation at all since the AC chargers are inefficient (~80%). So you use 1kWH of grid power to charge 0.8Ah into your battery which you then use to generate 0.60-0.64Ah of AC power for your appliances (meaning you spent 156% to 167% of the grid power you would have spent by powering direct).

Start with the consumption and the Solar power you can fit/afford and the figure out the correct inverter - don’t start by selecting the inverter...

 

[fafrd]

If you decide to use the solar power for an ‘island’ not tied to the grid, this inverter has enough power to drive your cooler and is only $135: https://www.amazon.com/gp/aw/d/B015...=UTF8&psc=1&pd_rd_i=B0154BQFDUp13NParams&th=1

This will mean you will need to unplug the cooler from the solar island and replug into grid power once the solar power is spent.

Batteries are ~$100 for a 50Ah (usable) 12V car battery or $100/0.6kwh (only enough to run your cooler on high for ~90 minutes straight, not much).

And sssuning you have ~500W of solar panels (which rarely exceed 400W of production, that translates to 16-20A charging a 12V battery or 8-10A charging a 24V battery.

People on this board rave about Epever MPPTs and you can get a 10A 24V Epever charge controller for $60: https://www.amazon.com/EPEVER-Controller-Negative-Grounded-Regulator/dp/B01BXRIRQC

So for under $200, you can get an 800W battery-powered inverter and a 10A SCC capable of charging a 24V battery with 500W of solar panels.

That still leaves you $200 to spend on a 50Ah 24V battery (2 x 12V batteries) which will allow you to squirrel away 1.2kW of daytime solar energy capable of powering your cooler for ~3 hours at night.

The Sunpower 1kW GTIL inverter will cost twice as much as the $135 Reliable inverter but will avoid you needing to switch the cooler to grid power in the middle of the night when the battery runs low...

Spending $400 on the right separate components on my opinion is a wiser investment than spending the same amount on the wrong all-in-one (and again, it’s primarily the grid-tied battery charger which is not going to help you at all...).

 

[Forbisher]

your math is wrong i think, it is not 0.127kwh, so my bill of $106.70 /841 equals 12.68 kwh, so 8 hours equals 101.44, so what does the 101.44 equal, dollars or cents.

That 101.44 is just $1 or 101 cents.

If you are limiting yourself to only one 250 watt panel then at your summer peak of 7 sun hours per day that 250 watt panel will only produce a maximum of 1750 watt hours per day or round it up to 2Kwh per day.

2Kwh at your low grid cost of about 13cents Kwh will only save you a total of 26 cents per day.
That's it. A lousy 26 cents a day.

A 1000 watts or more of panels would save more but you are limited to 250.

If this is a hobby or for education great but you are not going to be saving much off your power bill with 250 watts.

Adding a battery will result in no power savings.

$1.11 Kwh is like the cost of generating power from a diesel generator.

 

[roadrunner]

Understand. So you have a shed or something where you think you can hide two solar panels and where will you mount the GTIL inverter (and battery and SCC if you decide you need to go after some nighttime consumption)?

in my shed, i can hide 2 small panels on the roof, then anything else gets mounted on wall of shed or on work bench.

 

[fafrd]

in my shed, i can hide 2 small panels on the roof, then anything else gets mounted on wall of shed or on work bench.

Can you put one large panel on the roof of the shed (40” x 80” or 40” x 67”)?

So you’ll have one or two panels on the roof of the shed connecting down to an inverter and possibly battery+Solar Charge Controller in the shed, and the inverter will send power into the trailer through an extension cord, does that sound about right?

If so, the GTIL inverter may not be an option unless you run one extension cord out to the shed and then back into the trailer (the clamp-sensor needs to be within 6’ of the inverter).

 

[fafrd]

That 101.44 is just $1 or 101 cents.

If you are limiting yourself to only one 250 watt panel then at your summer peak of 7 sun hours per day that 250 watt panel will only produce a maximum of 1750 watt hours per day or round it up to 2Kwh per day.

2Kwh at your low grid cost of about 13cents Kwh will only save you a total of 26 cents per day.
That's it. A lousy 26 cents a day.

A 1000 watts or more of panels would save more but you are limited to 250.

If this is a hobby or for education great but you are not going to be saving much off your power bill with 250 watts.

Adding a battery will result in no power savings.

$1.11 Kwh is like the cost of generating power from a diesel generator.

 

[fafrd]

That 101.44 is just $1 or 101 cents.

If you are limiting yourself to only one 250 watt panel then at your summer peak of 7 sun hours per day that 250 watt panel will only produce a maximum of 1750 watt hours per day or round it up to 2Kwh per day.

2Kwh at your low grid cost of about 13cents Kwh will only save you a total of 26 cents per day.
That's it. A lousy 26 cents a day.

Yeah, that’s what I was trying to explain. If the goal is to save $25/month, a single 250W panel won’t come close (more like $8/month, best-case).

A single 450W or 500W gets 2/3 of the way there and if he can fit two standard-size panels, he should be able to save close to $25/day but will need a battery (to supply nighttime consumption).

A 1000 watts or more of panels would save more but you are limited to 250.

If this is a hobby or for education great but you are not going to be saving much off your power bill with 250 watts.

Adding a battery will result in no power savings.

Agree, unless the solar power being generated exceeds the cooler consumption during the day while the panels are generating that power...

$1.11 Kwh is like the cost of generating power from a diesel generator.

 

[Freep]

cant do it, i live in a trailer park and by their rules cant have anything out side on trailer, or anything on roof but a swamp cooler or air con. my swamp cooler is on side of house in middle of trailer in kitchen and living room window, i can hide 2 small panels on my shed roof which is behind my trailer, and is flat, so hard to tell anything is up there especially a flat panel thats only a 1.5 inch thick. and 38 inch x 29 inch.

Trailer parks are an inherently predatory business. I'd focus more energy on moving somewhere else. That's where you're going to realize your biggest savings in the long run.

 

[fafrd]

in my shed, i can hide 2 small panels on the roof, then anything else gets mounted on wall of shed or on work bench.

What is the dimension of the roof of your shed?

 

[roadrunner]

ok, i maybe thinking this wrong, lets say my cooler uses 222 watts when running, is that 222 watts an hour, and if so, if i add 200 watts from 2 panels, would those panels be producing 200 watts an hour. so in theory, i would be using 22 watts an hour, or basiclly almost running for free at that low power consumption. So i would be saving 200 watts an hour off my bill per month, if i save 2 dollars a day, 7 hours of running, that would be 60 dollars a month, not using the utility's 11cents,12cents, 7 cents per kwh ect, becaue my panels would be producing that savings amount, doesnt matter how much they put out to what the utility charges. my panels might put out 3x as much as what the utility charges, see my point.

 

[roadrunner]

What is the dimension of the roof of your shed?

6 foot x 10 foot

 

[Q-Dog]

The 250 watt SanTan used panels are approximately 40" X 65" so you could fit 3 of them up there with no room to spare. 2 should be easy.

 

[fafrd]

ok, i maybe thinking this wrong, lets say my cooler uses 222 watts when running, is that 222 watts an hour,

That would be 222Wh/hour or 0.222kWh/hour.

and if so, if i add 200 watts from 2 panels, would those panels be producing 200 watts an hour. so in theory, i would be using 22 watts an hour, or basiclly almost running for free at that low power consumption. So i would be saving 200 watts an hour off my bill per month,

During the peak part of the day, if you have a solar array putting out 200W of DC power, that will translate to 150-160W of power because budget inverters have efficiency of 75-80%. So you’ll need an array putting out 250-267W to generate 200W of AC power...

So for ~7 daylight hours you could reduce the energy consumed by your cooler from 222Wh/hr to 22Wh/hr, meaning from 1554Wh over that 7-hour daylight period to 154Wh, a savings of 1400Wh or 1.4kWh per day.

if i save 2 dollars a day, 7 hours of running, that would be 60 dollars a month, not using the utilitys 11cents,12cents, 7 cents per kwh ect, becaue my panels would be producing that savings amount, doesnt matter how much they put out to what the utility charges. my panels might put out 3x as much as what the utility charges, see my point.

The problem you have with your math is that you saved 1.4kWh per day, but your utility only charging you 12.7 cents per kWh, so that 1.4kWh in daily energy savings only added up to savings of less than 18 cents per day.

Savings of $0.18 per day x 30 days translated to saving only $5.40 per month (a looong way from your goal of saving $25/ month...).

 

[fafrd]

6 foot x 10 foot

As already stated, standard 60-cell panel length is 65”, so you need to decide whether ‘6-foot’ means you can hide 65” long panels up there or not.

And standard panel width is 39”, so 3 panels across equals 117” or just under 10’.

You can find new 310W panels for $135 today, so 930W of panels will cost you just over $400.

With 930W instead of 250W, you’ll be able to generate 3.72kW/day instead of 1.4kW and save $0.47/day instead of $0.18/day.

Saving $0.47/day translates to saving $14/month, still a ways from your goal of saving $25/month, but slot closer than only saving $5.40/month...

 

[roadrunner]

The 250 watt SanTan used panels are approximately 40" X 65" so you could fit 3 of them up there with no room to spare. 2 should be easy.

exactly, but cant go over the watts of my cooler so i wont get caught, but if i could use some kind of inverter that wouldn't back feed that would be perfect, 3 panels would probably cover more than the cooler, a little at least, maybe a ceiling fan or 2