Texas Off-Grid Barndo - Cold Weather Update

Setup summary

40’x 60’ two story metal barn with 3600 sf of heated space on two floors.
16Kw PV, three EG4 6000XPs and six EG4 LL-S batteries for 600a storage
5Kw manual generator and one EG4 Chargeverter
Two inverter heat pumps: 3 ton and 2 ton plus a 12K mini-split

More about the barn and solar setup here: Off-Grid Barndo

Texas cold weather update

The barn and system is perfect days where the temperature is above 35F.  No issues with power storage at night if I can get SOC to 80% before sunset.

The trouble started with the first Texas snow storm in December.  When the temperature dropped below 35F, the inverter heat pumps switch to emergency heat strips which quickly drained the batteries.  Peak consumption would exceed 15Kw multiple times per day.  To keep the system online and SOC above 20%, I have turned off the upstairs HVAC and set the downstairs unit to 60F at night and when SOC is below 80%.

In this graph the drain at night bottoms out at 14% SOC at 6AM and the system shuts down.  Big spikes in consumption occur when SOC gets to 26% and power is restored.  The downstairs heat pump maxes out the 15Kw heater coils when it turns back on and tries to get 60F set point.

After the first storm in December and low temperatures, the fastest thing I could do was buy an indoor ventless propane heater.  I setup a Mr. Heater 30K BTU vent free radiant indoor propane heater for the garage on a portable 40lb propane tank.  I have CO/CO2/propane air monitors for both the garage and living spaces.  The heater makes a huge difference for holding the whole barn temperature above 60F and keeping the battery from completely draining at night.  Unfortunately the 40lb tank supplies only 24 hours of propane at a low setting on the heater.  A second 40lb tank with an auto-switchover regulator gets me four to five nights at a cost of $15 per night of heat.

During the second storm, I installed an EG4 Chargeverter and hooked it up to a low cost 5Kw Harbor Freight generator.  The generator is able to run the Chargeverter at 90A, charge the batteries, and support a full HVAC load all night.  The Chargeverter and generator system is fully manual and the generator is way too loud for use as a permanent solution.  It has worked extremely well as a quick backup solution.  The Chargeverter was super easy to add to the system and use with the generator.  It is a must have addition to any off-grid system.

My end goal was to be fully off-grid with solar and batteries but after two storms with multiple days below 35F, I do not think adding another full rack of batteries for an additional 600a of backup is a complete solution.  Even having three full racks of batteries and 1800a of storage is would not be enough for a no-compromises off-grid house.  My system will require supplemental electricity and supplemental heat for extended cold weather.