We are starting construction documents on an off-grid cabin in in central Utah. Located at 7,200 feet in climate zone 5b, with a heating design temp of 15 F. Approx. 1,800 sq/ft, with open kitchen/living/loft area of approx. 1,100 and two smaller bedrooms. This will be used part time, but year-round. This will not be built to passive house standards, but we are aiming for Pretty Good House (or Almost Pretty good house.) Slab on grade. I’m also trying to avoid gas/propane as much as possible. We are not concerned about cooling at this location.
I’m looking for advice on winter heating. I was all set on Minisplits with propane generator to back-up charge my battery bank, but now I’m not sure if it’s the best option.
Goal: Keep the house at a consistent 40/50+ degrees all winter when not in use on minisplits (bumping up to 70ish and supplementing with wood stove when in use)
Solar:
405W x 36 = 14,580 Watt and approx. 23,588 kWh/year
Winter Production:
Nov – 1,902 kWh
Dec – 1,708 kWh
Jan – 1,978 kWh
Feb – 1,887 kWh
Energy:
- 64kWh battery bank
- Inverter TBD – Most Likely LF type
- Generator – TBD, but idea was to have a small propane based one for battery charging only.
- 80 gal HPWH
- Well Pump 1 ¾ - will eventually swap with either solar direct or Grundfos. Pumping to large cistern, so not as concerned about start-up. Will not pump much in the winter months.
- All other appliances will run off electricity
Minisplit Options:
I’m looking for advice on winter heating. I was all set on Minisplits with propane generator to back-up charge my battery bank, but now I’m not sure if it’s the best option.
Goal: Keep the house at a consistent 40/50+ degrees all winter when not in use on minisplits (bumping up to 70ish and supplementing with wood stove when in use)
Solar:
405W x 36 = 14,580 Watt and approx. 23,588 kWh/year
Winter Production:
Nov – 1,902 kWh
Dec – 1,708 kWh
Jan – 1,978 kWh
Feb – 1,887 kWh
Energy:
- 64kWh battery bank
- Inverter TBD – Most Likely LF type
- Generator – TBD, but idea was to have a small propane based one for battery charging only.
- 80 gal HPWH
- Well Pump 1 ¾ - will eventually swap with either solar direct or Grundfos. Pumping to large cistern, so not as concerned about start-up. Will not pump much in the winter months.
- All other appliances will run off electricity
Minisplit Options:
- 1 larger 12-18 sized system for the open area
- 1 multiple split for the two bedrooms/bathrooms (may just go with 2 smaller 1:1 units, but seems like overkill for these rooms)
- Can Minisplits be set to run at 40-50 F? I’m reading conflicting information. The Hyper Heats are intriguing, but if I have to run then at 60F, I’ll kill my batteries quickly.
- I am running PEX for hydronic system under poured slab – was going to leave this stubbed but not connected. Now I’m wondering if a hydronic system might be more energy efficient than multiple minisplits in this specific low heat situation.
- I just started research into hydronic systems and I’m having issues determining the most efficient solution to the challenge outlined with hydronic. It seems either an Air To Water Heat Pump or Electric Boiler would be the best options, but not much info out there to review.
- Everything I’m reading says solar water collectors aren’t spec’d anymore. I am trying to avoid this option if I can.