Manage your power bill like a process metric

You already know your power bill jumps around, some months more than others. What most small systems do not have is a number that tells them whether a spike is normal seasonal pumping or a pump quietly failing. The bill goes up, the manager gets asked about it, and nobody has an answer better than a shrug.

That gap is common, and it is fixable. Most systems already collect two numbers, kilowatt-hours off the electric bill and gallons off the totalizer or SCADA, but never divide one by the other. Without that division, a bad month and a failing pump read exactly the same on paper: a bigger bill.

Rung 2 on the manager track. It covers the one metric that turns your power bill into something you manage, how to read your demand charge, when rising energy use signals a pump wearing out, and when a VFD is worth the money.

Start tracking kWh per 1,000 gallons

kWh per 1,000 gallons (kWh/kgal) is kilowatt-hours used, divided by gallons pumped, times 1,000. Both numbers already exist somewhere in your records: kWh off the electric bill or a meter read, gallons off a totalizer or SCADA. Round to two decimal places and log it against the same period each time.

One reading tells you little. A baseline does. Track kWh/kgal over a stable 3 to 6 month window first, then watch for drift off that baseline. A jump of 15 percent or more over baseline is the standard trigger for an inspection.

For a gut check against your own number, US drinking-water systems average roughly 1.4 to 1.5 kWh per 1,000 gallons, though the real spread across utilities runs from about 0.8 to 4.3. A high number by itself is not an alarm. It is common, and it is usually fixable once you know where to look. At a groundwater system, pumping is close to the whole energy bill, about 99 percent of it, so this one metric covers nearly everything you spend on power.

Turn the number into dollars

Multiply kWh/kgal by your energy rate and you get cost per 1,000 gallons, the number a board reacts to. If you do not know your exact rate, $0.10 per kWh is a reasonable default for rough math, check your own bill for the real figure. At $0.10/kWh, a well running 2.5 kWh/kgal costs about 25 cents per 1,000 gallons pumped.

Dollars do two jobs a raw kWh/kgal number cannot: they tell you whether a repair or a new motor is worth the money, and they are the language that gets it approved. A board that hears "efficiency dropped" shrugs. A board that hears the dollar number, cost per 1,000 gallons times the gallons you pump every month, has something to act on.

Reading your demand charge

Your bill usually carries two different charges that reward opposite behavior. The energy charge prices what you used. The demand charge is based on your single highest kW draw in the billing period. It is often locked in by a monthly ratchet that keeps that peak on your bill even after it passes.

The demand charge can run as much as half the total bill. That means shaving your one worst peak, the moment two or three pumps happen to start at once, can save more than trimming total kWh across the month. Staggering starts is often worth more than any single efficiency fix.

Shifting heavy pumping to off-peak hours helps the energy-charge side, if your storage allows it. It is not free: longer water age from overnight-heavy pumping can call for more disinfectant, and overnight backwashing creates a residuals-handling problem to plan for, not discover after the fact.

Pump efficiency decay as a PM trigger

A rising kWh/kgal number is often the earliest sign that a pump is wearing out, weeks or months before it fails outright. On more than one well, the pattern is the same: a kWh/kgal spike builds in the months before a motor fails, then flattens back out once the motor is replaced. Two similar wells, similar horsepower, can run at double each other's energy per 1,000 gallons purely on condition and controls, which is why your own baseline matters more than comparing wells against each other.

A few thresholds turn that drift into a work order instead of a hunch:

• kWh/kgal up 15 percent or more from baseline: schedule an inspection.

• Starts per day up 25 percent or more with no demand change: check level sensors, bladder

• Specific capacity (gallons per minute per foot of drawdown) down 15 to 20 percent: investigate.

• Specific capacity down 30 percent or more: plan a rehab.

• Motor housing or VFD heatsink reading over 180°F: investigate.

tanks, and control logic first.

Starts matter because a motor pulls 6 to 8 times its running amps every time it starts, the hardest single event on bearings and impellers. Cutting short-cycling can add 10 to 20 percent to a motor's working life, on top of whatever energy it saves.

When a VFD pays for itself

A variable frequency drive (VFD) matches pump output to actual demand instead of running full-on and cycling off. It softens starts, cuts water hammer, saves energy, and extends motor life. It can also take a single-phase power feed and put out three-phase to the motor, useful where three-phase utility service is not available.

It is not automatic money. The drive itself uses about 5 percent of the motor's power just to run, and cable losses between drive and motor run from under 1 percent to over 10 percent, all of it showing up as heat. Pump efficiency also tends to fall at lower speeds. On a pump working against high static head, a small speed reduction can swing flow a lot, sometimes pushing the pump back toward shutoff, so a VFD can hurt more than it helps there.

The decision rule: size the pump correctly first, then add a VFD only where duty genuinely varies. Tiny sites or steady-demand sites may see little benefit. Where it fits, reported savings run up to about 11 percent from matching the best efficiency point, and up to 37 percent from the VFD itself when duty actually varies through the day.

Sizing mistakes cost more than the pump itself

The purchase price of a pump is under 10 percent of what it costs over its life. More than 80 percent of lifetime cost is the energy it burns, so a cheaper pump that runs inefficiently is the expensive choice, not the frugal one.

Oversizing is the most common and most expensive sizing mistake. Correcting it typically saves 15 to 25 percent of pumping energy. Motors run most efficiently near 75 percent of rated load and fall off sharply below 50 percent, so a motor loafing at light load all day is quietly wasting money. Even small machining changes move real energy: trimming an impeller diameter by 2 percent cuts power by roughly 8 percent.

A mismatched pump train can cost more than either pump alone. At the City of Everytown, a 15 HP well motor was feeding into a 7.5 HP booster. Removing the booster and upsizing the well motor to 20 HP produced a 700 percent improvement in efficiency. The fix was matching one pump to the job, not running two mismatched ones in series.

Running the most efficient equipment the hardest pays off too. One utility saved about $115,000, 12 percent, in a single year simply by running its lowest-kWh-per-million-gallon wells first and leaning on the less efficient ones only when needed.

A log that takes two minutes and survives turnover

The minimum viable pump log is short: kWh at start and end, gallons at start and end. Add GPM, runtime, starts per day, discharge PSI, and VFD frequency if you have them. If a reading is not available, write "unknown" and move on. Do not let a missing field stop the log.

Where it lives matters as much as what is in it. A shared spreadsheet that anyone on staff can update, with the formulas already built in, survives turnover in a way a paper log clipped to a panel does not. If it is not recorded, it did not happen, at least not in a form you can use to justify money later.

For a repeatable structure, the standard energy-program framework runs seven steps: commit, baseline, identify, quantify, change, evaluate, promote, with one person named to own it so the effort does not stall after the first month. You do not need a formal program to start. You need one number, tracked consistently, with a name attached to who checks it.

Next on the ladder: Capturing knowledge before it retires.