I mentioned in my last post how cool the temperature was after a cold front blew across southern California and into Arizona. The thermometer hasn’t touched 60 since we arrived in Lake Havasu City. When we were in Jojoba Hills, we also had a cold spell. I put about 18 hours on the generator running the heat pumps for two days while we were there. I wondered at the time how efficient that was. Would I have been better off running the propane furnace?
Our Onan 7.5kW Quiet Diesel generator consumes an average of a little over half a gallon of diesel fuel per hour. Diesel fuel is currently down to about two bucks per gallon – so let’s assume $1.20/hour fuel cost for the generator. Of course the generator isn’t just supplying electricity for the heat pumps – it’s also powering the hot water heater, charging the batteries through the inverter, allowing the use of the induction cooktop and microwave oven and any other 120-volt AC appliances.
I did some research and found that our Suburban model SF42F propane furnace requires 40,000 BTU/hour input. One gallon of propane supplies about 91,000 BTU, so the furnace will burn about 0.44 gallons per hour. It will also draw about 11.5 amps of electricity from the battery bank. Propane fuel prices seem to vary widely. I haven’t bought propane since January of 2014 and we still have over a quarter tank in our 44-gallon propane tank. I was told that I could find propane for as little as $1.20/gallon if I searched around or I could have propane delivered to my rig for about $2.60/gallon. That’s a pretty wide spread. If I split the difference and call it $2.00/gallon, I would burn about $0.88/hour of propane. But, I would still have to run the generator sooner or later to recharge the battery bank.
The owner’s manual for our Onan generator recommends a minimum of two hours per month of running time with at least a 50% load. Generators like to be run – sitting for long periods without running them can result in corrosion of the electrical windings and components and degradation of the fuel system. Running the heat pumps with the generator provides a sufficient load to get it up to full operating temperature.
When we’re plugged into a full hook-up site, there’s no question about it – use the heat pumps. Electricity is generally included in a full hook-up site, unless we’re on a deeply discounted monthly rate where the electricity is metered.
After crunching these numbers, I think I’ll continue doing what I’ve been doing. When we’re off the grid, I’ll use the generator and heat pumps as long as the ambient temperature is above 40 degrees. Below that temperature, the heat pumps become inefficient and we’ll switch to the propane furnace. Hopefully we won’t have to do that because one of our goals is to stay away from cold temperatures!
The lingering cold air mass made the past couple of days somewhat boring for me. I ventured out to pick up groceries at a Walmart Supercenter a few miles away on Monday. It was a cold ride on the scooter. Donna made salmon patties with canned wild Alaskan sockeye and served it topped with parsley mayo over a bed of mixed greens Monday night. It was delicious.
Salmon patties over mixed greens
Donna has mostly been tied up at her computer writing articles for Quill.com. She has one more to complete before close of business on Friday. She takes a break for about an hour each day to go for a walk or run in the area.
I’ve been reading most of the time. The cool temperature combined with 15-20 mph wind is keeping me indoors. I take a walk around the park to stretch out and get some fresh air. On one of my walks, I saw a rare motorhome here in the park. It was a GMC motorhome. These were built by General Motors at the Pontiac truck and bus plant from 1973 to 1978. They’re unique motorhomes that were considered ultra-modern at the time. General Motors is the only US car company that built complete motorhomes. They were designed for comfortable travel as well as camping.
GMC motorhome here in the Havasu Falls RV Resort
The chassis is a front wheel drive configuration. GM used the 455 cubic inch (7.5L) Oldsmobile engine from the Toronado coupled to the Turbo-Hydramatic 425 automatic transmission. They were built in 23-foot and 26-foot configurations. I read that 90% of the production was the 26- foot length.
GMC motorhome chassis – Wikipedia photo
These rigs were low to the ground due to the front wheel drive configuration and aerodynamic by motorhome standards. The example here in the RV park looks to be fully restored to showroom condition.
Today the weather should begin a warming trend. We should see temperatures in the 60s today, followed by the 70s this weekend. The warming trend is expected to continue next week with high temperatures reaching the 80s! We’ll get out and explore around the lake.