Off Grid Power Is a Load List, Not a Battery Box

A standby system in the desert Southwest is sized from a written load list, not from a catalog. You count what must run at once, in watts, then add the surge of the well pump or the compressor. Everything else, fuel, filters, belts, service dates, follows from that number and from the season it has to survive. This is also where off grid power stops being a box in a shed and becomes a document: a load list, a fuel plan, a service calendar.

What goes on the load list before anything is bought

Start with a sheet of paper and a column of watts. A refrigerator draws 150 to 400 running watts and roughly three times that at compressor start. A well pump is the hard one: a 1 horsepower submersible can pull 2,000 running watts and 6,000 or more at start. A pressure pump for a household system, a furnace blower, a few LED lights, a modem, a phone charger, a chest freezer, a microwave: each gets a number.

The list has two columns, essential and deferrable. Essential means the well, the refrigerator, one room of light, medical equipment if it is in the house, and the controls on a propane or gas appliance. Deferrable means the shop welder, the air compressor, the second freezer, the electric water heater. A generator sized to the essential column is smaller, burns less fuel and lasts longer than one sized to everything the panel can carry.

Sizing rule that agencies and manufacturers both repeat: running watts of everything on at once, plus the largest single starting surge, plus a margin. A 7,500 watt unit covers a small house with a well if the water heater stays off. A 12,000 watt unit covers the same house with the water heater and a shop circuit. The number is arithmetic, not brand loyalty.

A generator without those three is a machine waiting to fail on the night it is needed.

How a standby generator is sized from a real load list

A real load list is built from nameplates, not from memory. Read the data plate on the well pump controller, the refrigerator, the freezer, the furnace. Write down volts, amps, and whether the motor is capacitor start or not. Multiply volts by amps for running watts. For motors, multiply by three for starting watts unless the nameplate states a locked rotor code.

Then decide what runs at the same time. The well pump and the refrigerator can start together if the generator has the surge. The well pump and the electric water heater usually cannot. A transfer switch or an interlock kit forces that decision at the panel, which is the point: the hardware enforces the list.

County extension services and state energy offices publish worksheets for this. The numbers are agency figures, not ours. A household that writes the list before shopping avoids the common failure, which is a generator that runs the lights and trips on the pump.

Why air filters, oil and belts fail faster in desert heat and dust

Heat and dust are two separate problems that arrive together. Dust loads the air filter, and a loaded filter richens the mixture and raises exhaust temperature. Heat thins the oil and cooks the belt rubber. In the low desert, ambient air above 105 F already eats into the generator's rated output, because output ratings assume cooler air.

Service intervals that work in a temperate climate do not transfer. Air filters in a dusty yard or near a dirt road may need inspection every 50 hours and replacement far sooner than the manual's calendar suggests. Engine oil in continuous summer service is commonly changed at 100 hours or less rather than the 200 hour figure printed for mild conditions. Belts get checked for glazing and cracking at every oil change, not once a year.

Cooling is the other half. A generator in a shed needs air in and air out, with the exhaust pointed away from the intake and away from the house. A unit boxed in a lean-to with a single vent will derate itself or shut down on high temperature. The manual states clearance figures. Those figures are minimums, not suggestions.

How is fuel stored and kept usable across a hot season?

Diesel and gasoline both age, and heat speeds the process. Gasoline with ethanol absorbs water and can phase separate in a tank that breathes hot days and cool nights. Diesel develops microbial growth and varnish. A fuel plan for a desert standby system has four parts: quantity, container, treatment, rotation.

Quantity is the run time you need. A 10 kilowatt diesel generator at half load burns roughly 0.5 to 0.8 gallons per hour, so 100 gallons is on the order of 125 to 200 hours. That is agency and manufacturer data, not ours. A small town keeping a well and a clinic running should size the tank to the longest outage it expects, not to the average.

Container means a listed fuel tank, not a row of plastic cans in the sun. Above ground tanks need shade, a secondary containment, and a vent that does not pull dust. Treatment means a stabilizer for gasoline and a biocide plus water removal for diesel. Rotation means using the stored fuel in a vehicle or a tractor and refilling, so nothing sits through a full summer.

Propane stores better than either liquid in desert heat and does not phase separate, which is why many rural households keep a propane generator for the well and a smaller gasoline unit for tools.

What a small town keeps running when the line goes down

The list is shorter than a household's and the stakes are higher. A town of a few hundred people typically keeps the water system, the fire station, the clinic or the emergency shelter, one fuel point, and the communications site. Everything else waits.

Water first. A booster pump or a well pump on a transfer switch keeps pressure in the lines and keeps the storage tank from draining. Fire station second, because a structure fire during an outage has no hydrant pressure without it. Clinic or shelter third, for refrigeration of medication and for heat or cooling depending on the season. Communications fourth, because the cell site and the dispatch radio are how the outage gets managed.

A town that has written this list, tested it under load, and stored fuel for it is a town that can wait out a two day line failure. A town that has not is a town that discovers its priorities at midnight.

The maintenance calendar is read against the seasons

The desert gives two service windows. Before the monsoon, in late spring, the system gets a full service: oil, filters, belts, coolant, battery load test, fuel polish, transfer switch exercise under load. After the monsoon, in early fall, it gets an inspection: dust in the intake, water in the fuel, corrosion on terminals, rodent damage to wiring.

Between those windows, a monthly start and a short run under load keeps the battery charged and the fuel moving. An annual load bank test, if the town or the business can arrange one, proves the machine can carry the list it was sized for. The calendar is the part that fails first, because nothing breaks on the day it is ignored.

What this site will not do

We do not sell generators, fuel, filters or service. We do not rank brands or dealers. We read public documents, agency worksheets, manufacturer manuals and county records, and we say when a number comes from an agency rather than from us. The load list is yours to write.