My Google news feed is determined to feed me a constant supply of stories regarding Texas’ unprecedented drought and heat wave. The summer of 2023 in central Texas has been the one of the hottest and driest in recorded history. ERCOT, the organization that handles the flow of electric power for most of Texas, has made pleas to consumers for conservation, paid off Bitcoin Miners to shut down operation dear peak demand hours, and come very close to having to initiate rolling black outs. On the water front, lake levels and river levels are at all time lows, officials are urging conservation and a couple of weeks ago our neighborhood water provided announced that all outdoor watering was forbidden. Google also likes to feed me stories about how Texas development is booming.
Our homestead is not tied into electric power grid or our neighborhood water provider network so we are mostly(we also have a gasoline powered generator) dependent on our solar panels and battery bank for our power and rain water collection for our water. We’ve also added some development to the homestead this summer in the form of a guest cottage that has increased demand. In this article I’ll talk about what conservation measures we takes as “offgridders” to cope with high energy demands and a tenuous energy supply. I’ll also cover how we handle things with our limited water supply.
On sunny days in late June when the days were the longest we could collect 16+ kilowatt hours of power. We ran the 12,000 BTU (1 ton) mini-split air conditioner in our cabin continuously setting the thermostat down to 64° F (18° C) from 10 am – 5 pm and then turning it up to 76 – 78°F (24°-26°C) overnight. Even so, with daily temperatures swinging from a balmy 80°F (27°C) to a blistering 110° F (43°C) and with our mini-split evaporator(indoor unit) being located on the ground floor our sleeping loft started to become uncomfortably warm as the high heat persisted. In late July with loft temperatures hitting 83° F (28°C) we started sleeping in our newly constructed guest cottage. The guest cottage is partially earth-bermed and has a lot of thermal mass inside of a well insulated envelope so with a mini-split air conditioner it is able to maintain an average of 75° F (24°C) using around 4 kilowatt hours of power a day.
Currently, in September we’re less than a couple of weeks from the fall equinox and we’re only collecting 12-14 kilowatt hours of power a day and high temperatures have been in 104-109° F range. Now, in our cabin we run the air conditioner set at 78° F (26° C) from roughly 8 am to 9 pm and turn it off overnight. If our battery capacity reaches 100% in late afternoon we’ll run the A/C on its highest setting until it starts pulling from the battery bank and then set it back to 78°F (26° C). Overnight, the air temperature on the ground floor of the cabin creeps up to 82°F – 83°F (28° C) with the loft being a degree or two warmer.
In the guest cottage I have a fancier mini-split that I can program. It’s thermostat is set to 70° F (21° C) between 10 am and 3 pm (to charge the thermal mass) and then 75° F (24° C) between 3 pm and 10 pm. It shuts down between 10 pm and 10 am. Overnight, the air temperature will rise to around 76° – 79° F (26° C) although it seems to feel cooler because of the high thermal mass earthen walls and floor. A fan also helps a lot.
The daily power level of our 20 kilowatt hour flooded lead acid battery bank swings from ~68% to ~100%. Flooded lead acid batteries can only be discharged to 50% capacity so effectively we only have 10 kilowatt hours of storage. We have 3.9 kilowatts of roof mounted solar panels but given the loss of efficiency due to high heat among other factors we’re collecting around 2.7 – 3 kilowatts at peak times (12pm-4pm). I said earlier that we’re mostly dependent on our solar panels for power. We also have a 2000 watt gas powered generator that lately I’ve run for a few hours on three evenings in the past month when we play online board games with some friends. My desktop computer is a bit of a power hog and we typically run the air conditioner later.
Finally, during the summer we don’t cook inside in the evening. We either eat our main meal at lunch and have salad and sandwiches or grill outside in the evening.
Future Electric and HVAC Plans
I would like to add 1-2 kilowatts of solar modules to my existing array and get a bigger battery bank. Lithium Phosphate batteries have really dropped in price since we installed our system. I also want to upgrade our 12000 BTU (1 ton) mini-split air conditioner to an 18000 BTU (1.5 ton) two zone version in the cabin so I can put an evaporator unit in the loft.
I probably should have increased our electric generation and storage capacity before building the guest cottage. I had hoped with the partial berm, mechanical cooling wouldn’t be necessary but that turned out not to be case. I have a temperature probe located 5-6 feet down in the berm and currently in early September the ground temperature is in the low 80s° F (27° – 28° C). I only backfilled the berm in February so perhaps the ground temperature will be lower in the future after a full winter.
Also, during the past few more moderate summers our HVAC and electrical system have been sufficient and even running the air conditioner on its lowest temperature setting during the day we would have surplus power. Highs in the 110s versus the low 100s puts significantly more demand on the cooling system.
Water wise we’re not as regimented. When we built the cabin I made a hypothetical water usage spread sheet taking into account shower frequency and duration, dish washing, personal hygiene, laundry (we currently do laundry as my parents’ house next door), drinking and cooking and calculated that Jean and I would need 42 gallons of water a day. For almost two years I’ve been measuring our water usage and it turns out that our domestic daily rate(for two people) is 20 – 25 gallons of water a day. So, with our 3000 gallons of water storage I originally calculated would last us two and a half months or so, it turns out we can go 4-5 months. I credit the power of the composting toilet and Jean not showering 2 times a day like some other people in our household for our amazing water efficiency. We’ve received about ¾ of an inch of rain since mid June of this year which has bought us a week or two of water usage.
However, we have a nascent food forest with lots of 1-3 year old trees and shrubs. We received significant rainfall in May and early June but by July even with a thick layer of wood chips the plants were starting to look unhappy. My watering regimen was/is 5 gallons of water for every new tree and shrub once per week to simulate a deep penetrating rain and to try to train the roots to go deep rather than hang out at the surface. For our food forest it takes about 150 gallons of water a week (which is coincidentally about what our weekly domestic water consumption). I irrigated from our water supply (3000 gallons of storage) through July and into August. When our tanks got below 50% capacity I bought a 100 foot hose and hooked up to our next door neighbors’ faucet(with their permission) to water for a few weeks until the neighborhood water supplier announced the moratorium on outdoor watering.
We have 1100 gallons of rain water storage for the T-brick cob shed we built many years ago on my parent’s property (the aforementioned neighbors) that we rarely use because the tanks are in an inconvenient location. However, that problem was solved with a water pump and the aforementioned 100 foot hose. Hopefully, that solution will work until we get significant rainfall.
Apart from the switching irrigation water sources our water usage has not changed much. I recently installed an outdoor shower with an exquisite but extremely indulgent (2.5 GPM compared to our indoor low flow 1.25 GPM shower head) rain shower head and noticed the first week it was installed we averaged 30 gallons of water per day (I think one day I took five showers just because of the novelty). Since then I’ve just been taking Navy showers when using the outdoor shower. I’ll post about the outdoor shower soon but for now I’ll say it’s really beautiful and has a semi-transparent roof. In afternoons after I’ve sweated through my shirt multiple times and I’m slightly delirious from the heat I envision a day where I’m in the shower during a rain storm and I’m watching the rain drops splatter on the roof. Our water tanks are overflowing, and I have the shower running full on with not a care in the world. Oh, to dream….