Going solar!

SpaceBus

Minister of Fire
Nov 18, 2018
4,504
Downeast Maine
The blue line is cloud cover for today! :)

Making ~800w at the moment.

View attachment 253484
Wow, that's amazing. I'm hoping to have a solar system with storage operational in the next ten years. That's really great to see even 800w with such cloudy conditions. We have been working hard to reduce our usage to the point that we could go through winter with just solar.
 
  • Like
Reactions: mar13

begreen

Mooderator
Staff member
Nov 18, 2005
83,758
South Puget Sound, WA
Wow, that's amazing. I'm hoping to have a solar system with storage operational in the next ten years. That's really great to see even 800w with such cloudy conditions. We have been working hard to reduce our usage to the point that we could go through winter with just solar.
We're hitting 1kW today with clouds or about a fifth of system capacity, but it is frequently dropping to 200W as clouds scud by.
 
  • Like
Reactions: SpaceBus

SpaceBus

Minister of Fire
Nov 18, 2018
4,504
Downeast Maine
We're hitting 1kW today with clouds or about a fifth of system capacity, but it is frequently dropping to 200W as clouds scud by.
What kind of daily usage are you seeing, if you don't mind me asking? Right now we are around 11.5 KWhr/day average. I'd really like to get down to less than 9 KWhr/day
 

begreen

Mooderator
Staff member
Nov 18, 2005
83,758
South Puget Sound, WA
About 24kWh/day at this time of year. My wife is baking stuff for Christmas, heat pump comes on some times, winter lighting, electric HW and clothes dryer bring it up a lot and we charge the car too. Summer drops down to about 15kWh/day including car charging.
 
Last edited:
  • Like
Reactions: SpaceBus

Rob711

Feeling the Heat
Oct 19, 2017
345
Long Island, ny
1C32A7AC-B785-4D68-92F0-FB6BC4F62306.png
I love data! MY natural gas hot water heater is over 10 years old so I feel it should be replaced soonish. I’m not sure I wanna commit to electric on this yet. I briefly looked into on demand electric water heaters, wow those need some serious juice!
 

SpaceBus

Minister of Fire
Nov 18, 2018
4,504
Downeast Maine
About 24kWh/day at this time of year. My wife is baking stuff for Christmas, heat pump comes on some times, winter lighting, electric HW and clothes dryer bring it up a lot and we charge the car too. Summer drops down to about 15kWh/day including car charging.
Thanks for the data points. This makes me confident we could live with solar for the majority of the time.
 

semipro

Minister of Fire
Jan 12, 2009
3,852
SW Virginia
View attachment 253572 I love data! MY natural gas hot water heater is over 10 years old so I feel it should be replaced soonish. I’m not sure I wanna commit to electric on this yet. I briefly looked into on demand electric water heaters, wow those need some serious juice!
You should consider a heat pump water heater. They're more efficient that a resistance unit and they pull way less peak power - nice when you're on backup power whether solar, wind, or generator.
 

SpaceBus

Minister of Fire
Nov 18, 2018
4,504
Downeast Maine
You should consider a heat pump water heater. They're more efficient that a resistance unit and they pull way less peak power - nice when you're on backup power whether solar, wind, or generator.
I'm using an on demand electric water heater and it uses far less electricity than my old resistance unit. Sure, it takes two dual pole 40 amp breakers, but there only two adults and I have a 40 gallon tank heated by a coil in my cookstove doing the heavy lifting. Usually input sensor on the water heater never reads lower than 75 df and I have the output set at 130df. So far with the change over I'm using less than half of the power I was using previous.

My situation is far less than usual, but in the right situation electric on demand water heater heaters can be really great.
 

Where2

Feeling the Heat
Feb 3, 2013
364
South Florida
Usually input sensor on the water heater never reads lower than 75 df and I have the output set at 130df. So far with the change over I'm using less than half of the power I was using previous. My situation is far less than usual, but in the right situation electric on demand water heater heaters can be really great.
What temp does your water come out of the ground at SpaceBus? In South FL, mine comes out of the city water pipes at around 75°F. When I have washed my car at our farm in Maine, I managed to fog up the inside of the car windows on a summer day with that unheated north Maine ground water coming straight off my well pump in the basement. :rolleyes: Seems to me, my well water was somewhere between 47° and 52° in September.

My PV Watts calculations put the 4.6kW array I intend to install in Maine at ~5MWh/yr. That's ~685Wh per PV panel per day.
At our house in FL, my actual average is ~790Wh per PV panel per day. Our daily home consumption is basically double what we produce with PV when averaged across a year.
 
  • Like
Reactions: SpaceBus

sloeffle

Minister of Fire
Mar 1, 2012
684
Central Ohio
My HPHW water heater costs me between $5 - $7 a month to run. The HPHW I just installed will be even cheaper since it has a UEF of 3.45. I'm sorry but there is no way an on demand electric unit can make hot water that cheap. I doubt your can even make it that cheap with natural gas.

Simple electrical match ( V over I,R):

80 amps x 240 volts =19,200 watts

19,200 / 1000 watts ( 1kwh ) = 19.2kW

19.2kW * .14 cents ( my cost 1kWh of electric ) = $2.688 per hour to run

At $7 a month I'm using around 50kWh of electric all month to make my hot water.
 
  • Like
Reactions: semipro

SpaceBus

Minister of Fire
Nov 18, 2018
4,504
Downeast Maine
What temp does your water come out of the ground at SpaceBus? In South FL, mine comes out of the city water pipes at around 75°F. When I have washed my car at our farm in Maine, I managed to fog up the inside of the car windows on a summer day with that unheated north Maine ground water coming straight off my well pump in the basement. :rolleyes: Seems to me, my well water was somewhere between 47° and 52° in September.

My PV Watts calculations put the 4.6kW array I intend to install in Maine at ~5MWh/yr. That's ~685Wh per PV panel per day.
At our house in FL, my actual average is ~790Wh per PV panel per day. Our daily home consumption is basically double what we produce with PV when averaged across a year.
Wow, those are great numbers!

The well water is possibly even less than 42df. It's the coldest well water I've ever had, and my grandmother had a mountain spring fed well. On a day I'm using the cooker to heat and/or cook the water is more like 120df+ on the output. We do tend to use a lot more hot water now that it's almost free. My wife likes to take a lot of baths due to some pain from medical problems. I think in the future I will put an r7.5 wrap on my range boiler for a while. After we remodel the bathroom I plan to put a loop or two in the water coil in my stove to accommodate another 40 gal range boiler so we can get a 60" bathtub.
 

Brian26

Minister of Fire
Sep 20, 2013
502
Branford, CT
My HPHW water heater costs me between $5 - $7 a month to run. The HPHW I just installed will be even cheaper since it has a UEF of 3.45. I'm sorry but there is no way an on demand electric unit can make hot water that cheap. I doubt your can even make it that cheap with natural gas.

Simple electrical match ( V over I,R):

80 amps x 240 volts =19,200 watts

19,200 / 1000 watts ( 1kwh ) = 19.2kW

19.2kW * .14 cents ( my cost 1kWh of electric ) = $2.688 per hour to run

At $7 a month I'm using around 50kWh of electric all month to make my hot water.
I agree. I monitored my geospring and for just the wife and I it only used like a kwh or two a day. It was like $10-15 a month with CT's really high electric rates. Just to be connected to gas here the service charge is double that.

I also read those on demand units are horrible for the grid as well. They can put a serious strain on the equipment with that many amps surging when it comes on.
 

SpaceBus

Minister of Fire
Nov 18, 2018
4,504
Downeast Maine
My HPHW water heater costs me between $5 - $7 a month to run. The HPHW I just installed will be even cheaper since it has a UEF of 3.45. I'm sorry but there is no way an on demand electric unit can make hot water that cheap. I doubt your can even make it that cheap with natural gas.

Simple electrical match ( V over I,R):

80 amps x 240 volts =19,200 watts

19,200 / 1000 watts ( 1kwh ) = 19.2kW

19.2kW * .14 cents ( my cost 1kWh of electric ) = $2.688 per hour to run

At $7 a month I'm using around 50kWh of electric all month to make my hot water.

I agree. I monitored my geospring and for just the wife and I it only used like a kwh or two a day. It was like $10-15 a month with CT's really high electric rates. Just to be connected to gas here the service charge is double that.

I also read those on demand units are horrible for the grid as well. They can put a serious strain on the equipment with that many amps surging when it comes on.

That depends on the unit and the water temp. My unit can only pull 80 amps max which is an oven and washer running together. Since my ecosmart unit can modulate and detect input and output Temps it uses very little. I think last month we used 390 kwhr and it is on track to be 300 or less next month.

Here is what the power company told me I used. This involved dumping a few hundred gallons outside while getting my house plumbed. Certainly my experience is a typical since my input Temps are usually over 100df, if not much higher. If my wife doesn't spend 4 hrs in the tub the range boiler stays hotter of course. She won't be in the tub for at least four weeks, if not longer so I will really be able to compare.
 

Attachments

lml999

Minister of Fire
Oct 25, 2013
503
Cape Cod, Massachusetts
We had 37 SunPower panels installed 3 years ago, currently generating about 140% of our annual needs. Haven't paid a dime to the electric company in 3 years. :)

Silly squirrel tried to take up residence under the panels last summer...we chased him away with repeated dousings with a garden house. He's back, so we're having "critter" guards installed in January. Not a big deal, costs about $1K, will protect the wiring against hungry rodents. He didn't cause any damage last year, but I'm not willing to chance it. Good friend did have substantial damage from rodents chewing his wiring...

I'm ASSuming that the $1K is eligible for a 2020 fed tax credit as its part of the cost of my solar panel installation. I don't see anything in the tax instructions about expenses being limited to a one time event....
 

jetsam

Minister of Fire
Dec 12, 2015
4,720
Long Island, NY
youtu.be
So far the system has been generating about half of what we use- but that's with December weather. I had been hoping to switch to mostly-electric heat, but I'm putting that off to next year when I have the summer's solar credits built up.

It's making 177w right now with full cloud cover. The best panel is making 10w right now, and the worst one is making 7w (that's a 1-minute average).
 

Brian26

Minister of Fire
Sep 20, 2013
502
Branford, CT
So far the system has been generating about half of what we use- but that's with December weather. I had been hoping to switch to mostly-electric heat, but I'm putting that off to next year when I have the summer's solar credits built up.

It's making 177w right now with full cloud cover. The best panel is making 10w right now, and the worst one is making 7w (that's a 1-minute average).
I assume by electric heat you mean heat pumps. Electric resistance heat is not very efficient compared to heat pumps. They can produce 4 times the heat of electric resistance heat for the same energy consumption.

I have 2 12k hyper heats and solar and its the best combination. Practically free heat and I am not burning any fossil fuels. Here was a random day where my panels were powering my whole house, mini splits and sending power back to the grid.
Screenshot_20191225-185054_Monitor.jpg

An Air Source Heat Pump (ASHP) will typically produce around 4kW thermal energy for every 1kW of electrical energy consumed, giving an effective “efficiency” of 400%. It is thermodynamically impossible to have an efficiency of more than 100%, as this implies that more energy is being produced than is being put in. For this reason the performance is expressed as a Coefficient of Performance (COP) rather than an efficiency. The above example would be expressed as having a COP of 4. The reason that it appears that more energy is being produced than is consumed, is because the only “valuable” energy input is electricity used to drive the compressor and circulating pumps. The remainder of the energy simply transferred from a heat source that would otherwise not be used (such as the ambient air, ground or a river) so is not considered as an energy input.
cop_heat_pump_operation.jpg
 

jetsam

Minister of Fire
Dec 12, 2015
4,720
Long Island, NY
youtu.be
I assume by electric heat you mean heat pumps. Electric resistance heat is not very efficient compared to heat pumps. They can produce 4 times the heat of electric resistance heat for the same energy consumption.

I have 2 12k hyper heats and solar and its the best combination. Practically free heat and I am not burning any fossil fuels. Here was a random day where my panels were powering my whole house, mini splits and sending power back to the grid.
View attachment 254231

An Air Source Heat Pump (ASHP) will typically produce around 4kW thermal energy for every 1kW of electrical energy consumed, giving an effective “efficiency” of 400%. It is thermodynamically impossible to have an efficiency of more than 100%, as this implies that more energy is being produced than is being put in. For this reason the performance is expressed as a Coefficient of Performance (COP) rather than an efficiency. The above example would be expressed as having a COP of 4. The reason that it appears that more energy is being produced than is consumed, is because the only “valuable” energy input is electricity used to drive the compressor and circulating pumps. The remainder of the energy simply transferred from a heat source that would otherwise not be used (such as the ambient air, ground or a river) so is not considered as an energy input.
View attachment 254232
Resistive right now. Heat pump minisplits are the next thing on the menu. I think I have the wife sold on LG because of that stupid picture frame head they offer. But whatever gets it the green light, I guess! ;)
 

peakbagger

Minister of Fire
Jul 11, 2008
5,448
Northern NH
I caution that the COP of 4 is decidedly optimisitic depending on outdoor air temp. COP of air source minisplits drops as well as heat output drops with the outdoor air temp. I find the intersection of an increase in building heat load and decreased minisplit COP and output is around 20 to 30 F for my house. Many early adopters of cold climate mini splits I know also have this general range. The options are install extra units or have backup heat sources that are temperature independent.

Note the ASHRAE ratings really are not a good fit for colder climates. Its worth taking a look at this link from NEEP which has more realistic ratings for cold climate units, scroll down a bit and read the background section.
Here is link to a Mitsubishi unit grabbed somewhat at random. https://neep-ashp-prod.herokuapp.com/#!/product/28983 Note the COP at 17 F and 5 F plus notice the derate in heat output. COP is still 2 which is better than 1.0 for electric heat but the required air flow leads to drafts which for most people means they need to run a higher space temperature setting. I keep a cool house normally but I do have electric fan forced space heater in my bathroom for use when I take a shower. I heat up that small space with a COP of 1 versus heating up the entire house to higher temp with COP of 2.

Practically I also know of a dealer that sells and services rebuilt Monitor kerosene space heaters and they are getting a lot of business and new installs in coastal Maine in homes that thought air source minisplits were all they needed. Its nice fit except using the monitor during cold spells and then letting the air source units take over. The problem is that kerosene is expensive and in some areas hard to get. The heaters also are banned in some states as they were lumped in with older style Kerosun unvented heaters (Monitiors are thru wall vented very similar to pellet stoves. The market for these units was dead for years but they noticed a major uptick of late.
 
  • Like
Reactions: sloeffle

Brian26

Minister of Fire
Sep 20, 2013
502
Branford, CT
I caution that the COP of 4 is decidedly optimisitic depending on outdoor air temp. COP of air source minisplits drops as well as heat output drops with the outdoor air temp. I find the intersection of an increase in building heat load and decreased minisplit COP and output is around 20 to 30 F for my house. Many early adopters of cold climate mini splits I know also have this general range. The options are install extra units or have backup heat sources that are temperature independent.

Note the ASHRAE ratings really are not a good fit for colder climates. Its worth taking a look at this link from NEEP which has more realistic ratings for cold climate units, scroll down a bit and read the background section.
Here is link to a Mitsubishi unit grabbed somewhat at random. https://neep-ashp-prod.herokuapp.com/#!/product/28983 Note the COP at 17 F and 5 F plus notice the derate in heat output. COP is still 2 which is better than 1.0 for electric heat but the required air flow leads to drafts which for most people means they need to run a higher space temperature setting. I keep a cool house normally but I do have electric fan forced space heater in my bathroom for use when I take a shower. I heat up that small space with a COP of 1 versus heating up the entire house to higher temp with COP of 2.

Practically I also know of a dealer that sells and services rebuilt Monitor kerosene space heaters and they are getting a lot of business and new installs in coastal Maine in homes that thought air source minisplits were all they needed. Its nice fit except using the monitor during cold spells and then letting the air source units take over. The problem is that kerosene is expensive and in some areas hard to get. The heaters also are banned in some states as they were lumped in with older style Kerosun unvented heaters (Monitiors are thru wall vented very similar to pellet stoves. The market for these units was dead for years but they noticed a major uptick of late.
The technology is advancing rapidly using vapor injection compressors. My Gree is AHRI rated at a COP of 4.47. I believe that is a seasonal rating as most mini splits arent running in subzero weather all winter.

My Gree can put out almost its full rated output at -22 as well.
Screenshot_20191227-092116_Drive.jpg Screenshot_20191227-092130_Drive.jpg
 

lml999

Minister of Fire
Oct 25, 2013
503
Cape Cod, Massachusetts
Get the basics figured out first, like solar exposure and roof capacity. Is there a substantial portion of the roof sloping to the south? Will the roof support the weight?
Not sure why the weight question comes up so often.

The 'average" panel weighs about 40 lbs. My 37 panels weigh about 1500 lbs, roughly equivalent to one inch of snow covering a 40'x30' roof.

And panels tend to shed snow more quickly than roof shingles, so solar installations potentially will reduce the amount of weight carried by the roof in a snow storm...
 

jetsam

Minister of Fire
Dec 12, 2015
4,720
Long Island, NY
youtu.be
Not sure why the weight question comes up so often.
I pulled a light fixture so we could get an inspection camera into the attic space for the engineering crew when they were inspecting for my install. I asked what they were looking for aside from beam spacing, and the guy said "We're looking for 2x4s. I hate it when we find 2x4s."

In a related story, I once told a guy he couldn't use 3/8" sheathing for decking on a roof, and he said, "We stand on the beams, and it'll last long enough for the check to clear."

So from the outside, ya really never know if a roof can even hold up the weight of a roof, let alone any additional stuff like panels and snow!
 

peakbagger

Minister of Fire
Jul 11, 2008
5,448
Northern NH
I looked up that GREE unit on the NEEP site using the AHRI number listed on the catalog cut

Note the COP down in the colder temps, quite a difference between 4.47 and 1.85. I don't dispute that an air source minisplit COP is great for milder winter temps and its a fine supplemental heat source. I also note that if I plot the temps verses COP the trend line looks to hit 1 long before its gets to -21 F. Granted there are only three data points but the trend looks like a baseboard heater for heating up a spot location beats heating the entire space with a minisplit somewhere around 0 F.

The NEEP Semninar goes into why the ASHRAE values were not useful for units in colder climates.

Standard heating practice is to size the heating appliance for the design cold temp steady state outdoor air conditions. Using that basis there is the option to install multiple minisplits to deal with winter design temps but unless the far lower COP is factored in the homeowner who uses a seasonal COP is going to be quite cold on that cold day as they will be short 60% of the expected heating load, thus the recomendation that in cold climates the minisplit should be regarded as supplemental versus a primary heat source.

1577470207391.png 1577470882530.png
 
  • Like
Reactions: CaptSpiff

Brian26

Minister of Fire
Sep 20, 2013
502
Branford, CT
I looked up that GREE unit on the NEEP site using the AHRI number listed on the catalog cut

Note the COP down in the colder temps, quite a difference between 4.47 and 1.85. I don't dispute that an air source minisplit COP is great for milder winter temps and its a fine supplemental heat source. I also note that if I plot the temps verses COP the trend line looks to hit 1 long before its gets to -21 F. Granted there are only three data points but the trend looks like a baseboard heater for heating up a spot location beats heating the entire space with a minisplit somewhere around 0 F.

The NEEP Semninar goes into why the ASHRAE values were not useful for units in colder climates.

Standard heating practice is to size the heating appliance for the design cold temp steady state outdoor air conditions. Using that basis there is the option to install multiple minisplits to deal with winter design temps but unless the far lower COP is factored in the homeowner who uses a seasonal COP is going to be quite cold on that cold day as they will be short 60% of the expected heating load, thus the recomendation that in cold climates the minisplit should be regarded as supplemental versus a primary heat source.

View attachment 254250 View attachment 254251
The OP is on Long Island. His 99 percent design temp is 17 degrees which means 99 percent of the year his temperature is above that. 1 percent of a average year he is below 17. At his 17 degree 99 design temp it still has a cop of 3. I bet OP would easily average a COP near 3.5-4.

I am on the CT shoreline and rarely ever see subzero cold but I have a wood insert and 80k btu oil furnace if I need it for those rare polar vortexes. My 2 mini splits have been heating my entire house so far this winter.

I lived in VT for many years and its a completely different world up there temp wise.

I believe you are in New Hampshire where the 99 design temps are single and subzero. If I lived there I would only run my min splits in shoulder season. Down here they are amazingly efficient most of the winter.

I attached the 99 percent design temps for NY and New Hampshire.
Screenshot_20191231-102825_Drive.jpg Screenshot_20191231-102809_Drive.jpg
 
Last edited: