Will increasing solar on roof decrease electric bill?

[Newcsn]

We're hooked to 50 AMP service for 5-6 months in SWFL in our 06 Dynasty (8 house batteries). Was wondering if it made any sense to increase the solar on the roof of the coach (obviously lots of sun down here to soak up) & if doing so would offset a portion of our monthly electric bill?

My guess is that the house batteries (12v side) impact our electric bill minimally. I would think the fridge, induction cooktop, microwave & roof AC units (3) are the real hogs.

It appears most folks increase their solar because their boondockers. We very seldom boondock - except for an occasional Harvest Host.

Thanks for your input!

[cbr046]

The induction cooktop and microwave are power hungry but for short periods.  Your fridge is a small load but runs 50% of the time all day.  Your 3 AC units are the real hogs.  I doubt they're even connected to the inverter, which is fed by chassis batteries which are recharged by solar.

If nothing else those panels shade your roof resulting in less air conditioning needed. 

Can you share the cost with the park owner for an external roof?

- bob

[Rocketman3]

It could but…

You need an expert on your inverter to know if there is an easy way to reduce your 120v grid usage other than flipping the pedestal breaker off. 

i have changed out my inverter to a Victron Multiplus. Let me give you a the two ways to handle that in the Victron system and maybe you can translate them to your system.

1. I can easily change the inverter from  “On” to “inverter only”. This ignores the grid power. So the solar charges the batteries and the 12v and inverter uses the power.  Manual process with all the limitations of the battery bank and inverter size.

2. With Victron system that includes a shunt, inverter and GX Device (Cerbo- master communications device), I can setup some “assistants” (internal programs) that can automatically change the inverter from “On” to “inverter only” depending on criteria. So if the loads go over _____watts (user setable) for 1 second the inverter pulls from the grid, or when the batteries get below ______% state of charge, the inverter switches on - so it charges the battery. You also have to setup the parameters to turn it back to inverter only too.  Then you set a bypass so if you start the generator when boondocking it can charge up and will not just ignore the power.  
 

I haven’t done it yet because it involves running a pair of wires between the GX device and the inverter (and that will be a bit of a chore in my rig). And we usually boondock and are not in campgrounds.

The other thing this does is it keeps the batteries not at 100% which will be a good thing for my Lithium’s.

FYI - I have 1500w of solar

Edit: I forgot to add one important item - the Victron inverter has an assisting mode so it can assist the grid.  But it probably can’t help offset the air conditioners without massive expenditures.

Edited March 11 by Rocketman3
Added info

[Newcsn]

14 minutes ago, cbr046 said:

The induction cooktop and microwave are power hungry but for short periods.  Your fridge is a small load but runs 50% of the time all day.  Your 3 AC units are the real hogs.  I doubt they're even connected to the inverter, which is fed by chassis batteries which are recharged by solar.

If nothing else those panels shade your roof resulting in less air conditioning needed. 

Can you share the cost with the park owner for an external roof?

- bob

Thanks @cbr046 makes total sense! We’re not at a park where external roofs are acceptable!

15 minutes ago, Rocketman3 said:

It could but…

You need an expert on your inverter to know if there is an easy way to reduce your 120v grid usage other than flipping the pedestal breaker off. 

i have changed out my inverter to a Victron Multiplus. Let me give you a the two ways to handle that in the Victron system and maybe you can translate them to your system.

1. I can easily change the inverter from  “On” to “inverter only”. This ignores the grid power. So the solar charges the batteries and the 12v and inverter uses the power.  Manual process with all the limitations of the battery bank and inverter size.

2. With Victron system that includes a shunt, inverter and GX Device (Cerbo- master communications device), I can setup some “assistants” (internal programs) that can automatically change the inverter from “On” to “inverter only” depending on criteria. So if the loads go over _____watts (user setable) for 1 second the inverter pulls from the grid, or when the batteries get below ______% state of charge, the inverter switches on - so it charges the battery. You also have to setup the parameters to turn it back to inverter only too.  Then you set a bypass so if you start the generator when boondocking it can charge up and will not just ignore the power.  
 

I haven’t done it yet because it involves running a pair of wires between the GX device and the inverter (and that will be a bit of a chore in my rig). And we usually boondock and are not in campgrounds.

The other thing this does is it keeps the batteries not at 100% which will be a good thing for my Lithium’s.

FYI - I have 1500w of solar

Thanks @Rocketman3 I follow your thought process & the equipment you use! However, the cost of 1500w of solar, Victron system & the necessary devices probably would have a real long breakeven period - and given we’re not boondockers, it would not be an advantage to us there either. 

[Tdkkart]

 There is more than 1 inverter, including some Victrons on the market that will do "power sharing", ie: use solar when there's solar available, and will sync up and use shore power as needed to either fully replace or augment the solar. 

So, yes, in your case the solar can indeed be used to offset the power that would normally go through the meter.  Whether you can get enough to offset the cost of the solar equipment involves some math, including some "save the planet feel good", or some "just because I can" multiplier.

 

[Benjamin]

As cbr046 said, the biggest impact would be if you could mount the panels off the roof to shade as much as you can to reduce AC. 

As Rocketman3 said, some inverters can do exactly what you want, but it has trade offs, and is not simple.  With LA batteries you want the batteries 90+% charged, Li you want 50% charge, and neither cycled while connected to the grid, so the inverter should handle all the solar production and put that into the grid, not touch the batteries besides an occasional top up.  There are lots of micro inverters that can handle that grid tie if your existing inverter can't be set up that way. 

Whether it's worth it depends on your KWH cost and how long you expect it to pay off for.  And probably most of all, how much you like tinkering with things like this.

[Tom Cherry]

38 minutes ago, Newcsn said:

We're hooked to 50 AMP service for 5-6 months in SWFL in our 06 Dynasty (8 house batteries). Was wondering if it made any sense to increase the solar on the roof of the coach (obviously lots of sun down here to soak up) & if doing so would offset a portion of our monthly electric bill?

My guess is that the house batteries (12v side) impact our electric bill minimally. I would think the fridge, induction cooktop, microwave & roof AC units (3) are the real hogs.

It appears most folks increase their solar because their boondockers. We very seldom boondock - except for an occasional Harvest Host.

Thanks for your input!

Here’s my EX Industrial & Manufacturing & Facility Engineer’s analysis.  

First, determine what load comes from the interior or Inverter and what load is from the “NON INVERTER” side.  Simple way to do this….Look at the billing cycle….  Do you have a meter on the Pedestal or somewhere that you can read daily?  You have to know the KWH for a given time frame.

Next, temporarily wire in TWO KWH Meters.   You can purchase a KWH meter on Amazon.  You need to find one that is rated for 3 or so KWH….and it is 120 and NOT 220.  You have a Sub Panel.  There are two 30 Amp breakers.  Using #10 wire, you disconnect the incoming power from each 30 amp breaker.  Then you wire nut in an outlet or connect each one to the 30 Amp lines.  Then the “outputs” of each meter has to be connected to the 30 Amp breakers….  Now each side is feeding through the meter.  Now the meters are recording the KWH on each side.  Then you collect data for a specific time….at least a week.  You also collect the TOTAL KWH for your service.  

Next up….subtract…. Probably the BULK is coming from the NON INVERTER side.  IF SO….you aren’t going to save anything.  You HAVE to have an inverter that can power many of the other loads like the Aquahot electric, the AC’s or HP.  Look at it this way.  You have 50 Amps of two leg power coming in.  That is roughly 100 Amps times 120 VAC or 12,000 watts or 12 KWH.  Your inverter is only rated for 2000 watts or 2 KWH.  Right now, when you are on shore, the inverter is “passing through” that 2 KWH.  In order for Solar to WORK….you would have to have a 12,000 watt inverter.  This is TOTALLY OFF THE GRID gear.

Then….most folks put in a max of 1,000 watts of solar.  At your peak, you consume TWELVE TIMES THAT AMOUNT.  SO, additional banks of batteries.  

Bottom LINE….Solar is designed for “powering”,  via your House Bank, the Inverter.  So, that allows you to BOONDOCK.  If you had a permanent pad and lot and put in an external solar farm, assuming you have NOT used your LIFETIME max solar credit, then you would be able go use the solar and sell it back to the Utility.  Lots of subsidized installations out there.  But the BULK of your usage is probably NON INVERTER….

So, without a heavy cash outlay for a larger inverter and a larger battery bank, it is not economically feasible.  All the off grid and advertising is based on Government subsidies…..and even if you qualified, your solar farm would be limited to 1000 watts.  ODDS ARE, you probably average 5 - 6 KWH during the peak.  

NO WAY…but if you want to measure ….then do it…but remember what goes through the Main Panel is 6 times what your inverter is capable of…..

[Newcsn]

15 minutes ago, Tom Cherry said:

Here’s my EX Industrial & Manufacturing & Facility Engineer’s analysis.  

First, determine what load comes from the interior or Inverter and what load is from the “NON INVERTER” side.  Simple way to do this….Look at the billing cycle….  Do you have a meter on the Pedestal or somewhere that you can read daily?  You have to know the KWH for a given time frame.

Next, temporarily wire in TWO KWH Meters.   You can purchase a KWH meter on Amazon.  You need to find one that is rated for 3 or so KWH….and it is 120 and NOT 220.  You have a Sub Panel.  There are two 30 Amp breakers.  Using #10 wire, you disconnect the incoming power from each 30 amp breaker.  Then you wire nut in an outlet or connect each one to the 30 Amp lines.  Then the “outputs” of each meter has to be connected to the 30 Amp breakers….  Now each side is feeding through the meter.  Now the meters are recording the KWH on each side.  Then you collect data for a specific time….at least a week.  You also collect the TOTAL KWH for your service.  

Next up….subtract…. Probably the BULK is coming from the NON INVERTER side.  IF SO….you aren’t going to save anything.  You HAVE to have an inverter that can power many of the other loads like the Aquahot electric, the AC’s or HP.  Look at it this way.  You have 50 Amps of two leg power coming in.  That is roughly 100 Amps times 120 VAC or 12,000 watts or 12 KWH.  Your inverter is only rated for 2000 watts or 2 KWH.  Right now, when you are on shore, the inverter is “passing through” that 2 KWH.  In order for Solar to WORK….you would have to have a 12,000 watt inverter.  This is TOTALLY OFF THE GRID gear.

Then….most folks put in a max of 1,000 watts of solar.  At your peak, you consume TWELVE TIMES THAT AMOUNT.  SO, additional banks of batteries.  

Bottom LINE….Solar is designed for “powering”,  via your House Bank, the Inverter.  So, that allows you to BOONDOCK.  If you had a permanent pad and lot and put in an external solar farm, assuming you have NOT used your LIFETIME max solar credit, then you would be able go use the solar and sell it back to the Utility.  Lots of subsidized installations out there.  But the BULK of your usage is probably NON INVERTER….

So, without a heavy cash outlay for a larger inverter and a larger battery bank, it is not economically feasible.  All the off grid and advertising is based on Government subsidies…..and even if you qualified, your solar farm would be limited to 1000 watts.  ODDS ARE, you probably average 5 - 6 KWH during the peak.  

NO WAY…but if you want to measure ….then do it…but remember what goes through the Main Panel is 6 times what your inverter is capable of…..

@Tom Cherry you're always a treasure trove of very practical knowledge - thank you!!! You've confirmed what I suspected - the prospect of "cost savings" via solar is virtually non-existent in our scenario! Thanks once again!

[96 EVO]

The way I see it is you can save on 'paid' power with solar / batteries IF you don't need air conditioning.

[Newcsn]

5 hours ago, 96 EVO said:

The way I see it is you can save on 'paid' power with solar / batteries IF you don't need air conditioning.

Well, @96 EVO no AC?! That ain’t happening in on this rolling ranch! So, for this & other reasons, solar was a quizzical apparition!! Thanks

[hitechpete]

How much solar do you currently have? We currently live in our Cedar Creek Champagne 38EFK, and our landlord kindly allowed me to install 4x 400 Watt ground mounted solar panels which we use solely to charge our 2 x12V batteries, I have however been able to maximise my 12V usage. I installed a programmable WiFi 120v socket on my converter, which allows my solar panels to power all my 12V appliances according to a schedule. I also installed the same type of device onto the mains input of my inverter, which powers my residential fridge. By programming this second device to interrupt the power (scheduled), it causes the inverter to power the fridge which since the converter is also off, has to pull its power from the batteries and therefore uses more solar power.

As we live in the UK, the opportunity to generate solar power is mainly limited to the summer months, I have however produced 545kWh since 2022 (see the two screenshots below).

I would imagine that any location giving regular sunshine would easily allow almost full power for most of the day.

[Ivylog]

Since you do not dry camp NO… no payback!  We Snowbird in SE Fla with 900W of solar (diy for $1200) and 600AH of Lithiums (diy for $1800 2 years ago). ..$3000 total. Even dry camping in the summer for 40-50 days puts the payback at 10+ years which will likely age me out.

In the winter I’ll shut the 50A breaker off inside and use the inverter to power things  unless AC is necessary, like today plus doing laundry. Any time a high amp item is used for more than 2 minutes, I turn the 50A back on until finished as the batteries will not make it through the night unless I turn the TV/Sat receiver breaker off. Most winters this works fairly well but this winter with all the rain and overcast days I can only turn the charger off… leave the 50A on 24/7.

During the summers I’ve had mixed results with the solar being enough to not run the generator. This past summer (hottest on record) was one of the best (dispute the hype about it being hot) as we were able to park in the sun unlike most summers where we park in the shade. In 6 days I might have to run the generator 3-4 hours, mainly when using the induction or topping the batteries off at night. I did shut the TVs off which negates fast forwarding through the commercials.

 

[Newcsn]

29 minutes ago, Ivylog said:

Since you do not dry camp NO… no payback!  We Snowbird in SE Fla with 900W of solar (diy for $1200) and 600AH of Lithiums (diy for $1800 2 years ago). ..$3000 total. Even dry camping in the summer for 40-50 days puts the payback at 10+ years which will likely age me out.

In the winter I’ll shut the 50A breaker off inside and use the inverter to power things  unless AC is necessary, like today plus doing laundry. Any time a high amp item is used for more than 2 minutes, I turn the 50A back on until finished as the batteries will not make it through the night unless I turn the TV/Sat receiver breaker off. Most winters this works fairly well but this winter with all the rain and overcast days I can only turn the charger off… leave the 50A on 24/7.

During the summers I’ve had mixed results with the solar being enough to not run the generator. This past summer (hottest on record) was one of the best (dispute the hype about it being hot) as we were able to park in the sun unlike most summers where we park in the shade. In 6 days I might have to run the generator 3-4 hours, mainly when using the induction or topping the batteries off at night. I did shut the TVs off which negates fast forwarding through the commercials.

 

Thanks @Ivylog you've confirmed my suspicions - not a worthwhile endeavor for us! Have a super day!

[Capt. Tango]

I have 1600 watts of flat mounted solar on the roof powering a 600 AH battery bank. I have an Aqua Hot unit so heating and hot water is not electric and our refrigerator is 120 AC. I'm parked 6 months in Arizona, I mostly run off battery power and only connect to shore power every 2-3 nights or when air conditioning is seldom needed. I use a 3,000 Watt Magnum Energy charger/inverter but need to check into the Victron units that have the "assist" feature. We generate an average of 6 KWH daily and see a 25% to 30% reduction in our power bill.

This set up will handle all the high amp devices (one at a time) even for extended periods, even 1 one of the 1.5kw AC units for about an hour.

[Capt. Tango]

Rocketman3 You peaked my interest. I have a Magnum Energy charger/inverter, do you know if I can add Victron components to my system to automatically control shore power when needed?

[Rocketman3]

I doubt it (without replacing the inverter)- because it uses programs (assistants) in both the Cerbo (computer) and the Multiplus (inverter/charger).

Here is one of three videos that discuss how to set it up and program it. There are several slightly different ways. Adam’s channel has the other two as well - his use is for a home - but RV would work too.

Now if you really wanted/needed to do this - here is a list of equipment that would be needed for MotorHome :(all Victron stuff):

shunt - Smartshunt or BMV712

inverter - MultiPlus 12/3000 2x120v

GX device - Cerbo (and touch)

solar if needed (really can use any solar charge controllers) Smart MPPT Solar charge controllers - (sized for your array).

plus a few connector data cables.

 

[Jetjockey]

Unless you are in a very low load demand situation . NO. My motorhome uses between  60 to 80watts to  power the dc control circuits which  run all the time. So in mountain dry camping  on a sunny day two 100watt panels will keep the system charged. panels help  keep my auto genstart from starting .I can use the inverter for larger ac loads but then the gen may start to pick the load up as batteries voltage decreases. To get enough solar to offset your energy cost you are going to have to invest in a larger panel array and likely lithium batteries with new controllers. Everyone situation is unique. I have put solar on a motorhome and pickup camper. For me it is mainly to keep the batteries up when not in use and no shore power available. Have a friend with an all electric prevost. He has 2 4000 watt inverters and eight 8d batteries . He can run a lot but still cannot recover with any solar panel array.