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.
weather.cod.edu
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
Thanks for the data points. This makes me confident we could live with solar for the majority of the time.
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.
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.
Seems to me, my well water was somewhere between 47° and 52° in September.
Wow, those are great numbers!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.
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.
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.ccASHP Specification & Product List | Northeast Energy Efficiency Partnerships
Click here to accessneep.org
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.
neep-ashp-prod.herokuapp.com
I looked up that GREE unit on the NEEP site using the AHRI number listed on the catalog cut
ASHP
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.
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