Churches, solar and demand charges: cutting peak demand on a fixed budget

Look at a church's electric bill next to a convenience store's and you will see two buildings that use similar amounts of energy paying very different amounts of money.

The convenience store runs coolers, lights, and HVAC at a steady rate around the clock. Its consumption is high and its peak is not much above its average. The church sits nearly empty from Monday through Saturday, with a small office load and a setback thermostat, and then on Sunday morning goes to full HVAC in the sanctuary and the fellowship hall, full lighting, the kitchen, the sound system, and the projection equipment, all inside a few hours.

The church uses far fewer kilowatt-hours. It can easily pay a larger demand charge.

Load factor is the whole story

Utilities and demand engineers describe this with a single number: load factor. It is the ratio of the energy you actually used to the energy you would have used if you had run at your peak demand continuously for the whole billing period.

The calculation:

Bill Brayden, who invented the Energy Sentry controller and has been sizing these systems since 1978, calls load factor "electrical miles per gallon." His rule of thumb is blunt. A building in the 10 to 30 percent range is an excellent demand control candidate. A building above 50 or 60 percent usually is not worth touching, because there are no peaks to flatten.

Churches sit at the good end of that range almost by definition. The same characteristic that makes the bill feel unfair, paying for capacity that stands idle six days a week, is exactly what makes the building easy to improve. There is a lot of headroom between the Sunday peak and everything else.

There is a second version of this that matters more

Beyond simply reducing the demand charge, some buildings are sitting just above a utility's threshold between a small general service rate with no demand component and a medium general service rate with one.

The gap between those two rate classes is not incremental. A congregation sitting at 52 kW is on the expensive rate. The same congregation held reliably under 50 kW is on the cheaper one. That is not a savings percentage, that is a different bill entirely. For a church with one Sunday peak and six quiet days, holding under a threshold is frequently achievable.

Ask your utility, or ask us, what the threshold is on your tariff and where your peak actually sits relative to it. It is the first question worth answering.

The fixed-budget reality

Church finance does not work like commercial finance. There is no capital budget line waiting to be spent. Money is donated, the annual budget is set by a committee, and any unbudgeted expense competes directly with the roof, the van, the youth program, and staff compensation. A finance committee made up of volunteers is going to be appropriately skeptical of an energy vendor with a slide deck.

So frame it the way the committee will have to frame it to the congregation:

1. State the current cost, not the savings.

Pull twelve months of bills and add up only the demand charge line. That is the number. It is a real, recurring, already-approved expenditure that nobody voted for. "We are spending $X a year on demand charges" lands differently than "you could save $X."

2. State the payback in months, from real bills.

Take the annual demand charge total, estimate the reduction from a load study of the actual building, and divide the installed cost by the annual reduction. If the answer is under three years, say so plainly. If it is seven years, say that too. A committee that catches you overstating once will never trust the second number.

3. Separate verified from estimated, out loud.

Any figure we give you is either taken from your bills and your published tariff, or it is an estimate stated as a range with the assumptions written down. We do not blur those two categories. That distinction is the reason our numbers are worth anything.

4. Account for the demand charge not going away on its own.

Unlike a repair, this cost recurs every month indefinitely and moves with rate cases.

Stacking with solar

Many congregations already have solar, often donated or grant-funded, and reasonably ask whether that makes demand control unnecessary.

It does not, and the reason is structural rather than a criticism of solar. Solar reduces kilowatt-hours. The demand charge is not priced on kilowatt-hours. It is priced on the single highest demand interval of the month, and a passing cloud during the Sunday service, a soiled array, or an inverter fault at the wrong moment is enough to expose the full building load to the meter for that interval.

The two work well together precisely because they address different lines on the bill. Solar takes down consumption. Demand control takes down the peak. Neither one does the other's job.

The public case that shows this most clearly is Mountain View Methodist Church in Boulder, Colorado. Before the project, the church was paying $10,633 per year in electricity costs. After installing solar together with Energy Sentry demand control, that figure came down to $168 per year.

That is one building, on one tariff, with one load profile, and no other church should assume the same result. But it does show what happens when the kWh product and the kW product are applied to the same building at the same time. Read more in our guide on solar and demand control, or the full churches industry guide.

How the system handles a church

Church buildings are not wired like houses. Rooftop units are distributed across the roof, the kitchen is far from the electrical room, and running new control wiring across a finished sanctuary is expensive and disruptive.

The commercial DAC handles this with power line carrier. A transmitter at the main distribution panel sends a control signal at 270 kHz over the copper already in the walls, and receiver modules mounted in the electrical compartment at each controlled load pick it up. Range is roughly 2,000 wire feet. That eliminates most of the conduit and labor that would otherwise make a commercial retrofit uneconomical, which matters a great deal when the budget is donated.

The controller itself watches total service demand through current transformers on the incoming mains, samples 1,000 times per second, and acts on how fast demand is rising rather than waiting for a limit to be crossed. On a Sunday morning, when the sanctuary units, the fellowship hall units, and the kitchen all come up at once, it staggers them by minutes so they do not all land inside the same interval. The service still starts on time and nobody in the pews notices anything.

Energy Sentry has been building demand controllers since 1978, with more than 35,000 installations in the field. Every system carries the IES Limited Warranty: 5 years on parts and 1 year on labor.

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Questions about your own setup? Call toll free (888) 461-9336, direct (970) 461-9600, or email help@energysentry.com. Monday–Friday, 8:00 AM–5:00 PM Arizona time.