Churches: the textbook demand-control candidate

The load profile

A church building is empty most of the time and full for a few hours a week. Sunday morning, Wednesday evening, and whatever else the calendar holds. The rest of the week the sanctuary sits dark.

But the equipment does not scale down. A sanctuary sized for 300 people needs rooftop units sized for 300 people, and on Sunday morning at 8 a.m. every one of them starts at once to pull the room from overnight setback down to comfort before the first service. Add the fellowship hall, the kitchen if there is coffee service, the sound and lighting systems, and the education wing.

That single Sunday morning startup is very often the peak for the entire month. It happens once. It lasts under an hour. And the church pays for it thirty days.

Load factors in the 10 to 30 percent range are common. Bill Brayden calls churches the poster child for demand control, and the arithmetic is why.

Why it is an unusually good candidate

The value of demand control scales with how spiky your curve is. Flat buildings have nothing to give. Churches have a curve that is essentially flat with two enormous spikes on it, which means shaving the spikes barely touches operations.

The other structural advantage is that a church has slack in its schedule that a restaurant or a hospital does not. If the sanctuary comes up to temperature over 90 minutes instead of 45, nobody is late for anything. Startup can be staged deliberately across a longer window, which is exactly what demand control does.

Churches are also the classic rate-class threshold case. Many utilities separate small general service from medium general service at a kW threshold, and the medium rate carries both a much higher service charge and a demand charge. A church sitting at 52 kW that can be held under 50 kW does not just reduce a demand charge, it changes which tariff it is billed under. That is often worth more than the demand savings themselves.

Some utilities also publish a specific tariff for houses of worship with a demand component. APS has one. Evaluating a church means reading that specific schedule, not the general commercial one. Current demand charge rates are confirmed per customer during tariff analysis.

Which loads get controlled

Rooftop HVAC units are the whole game in most churches. A sanctuary with four or five rooftop units, a fellowship hall with two more, and an education wing with several small systems gives a controller plenty to sequence. Units are grouped so they rotate rather than compete, and compressor protection timers keep every unit within its manufacturer limits.

Beyond HVAC: kitchen equipment where present, particularly electric ovens and warmers used for fellowship meals. Electric water heating. Baptistry heaters, which are large, intermittent, and almost always run at the worst possible time. Parking lot and exterior lighting on larger campuses.

Most church buildings have loads distributed across a large footprint, so control is delivered by power line carrier rather than hardwired relays. A transmitter at the main distribution panel sends a signal over the building's existing copper wiring, and receivers at each rooftop unit act on it. That avoids running control wire across a building and is what makes the job affordable.

Multi-meter campuses need one more step: identifying which meter is actually on the demand rate. Larger churches frequently have several services, and only one or two of them are worth addressing.

What the buying process looks like

Start with the interval data. Twelve months of it will show the Sunday spike clearly and give you a load factor in one calculation. Most church business administrators can pull this from the utility's online portal in a few minutes.

Then the tariff. We want to know the demand charge per kW, whether demand is billed 24/7 or on-peak only, whether there is a ratchet, and where the rate class thresholds sit. If a threshold is in play, we model both scenarios.

Then a site walk. How many rooftop units, where is the main distribution panel, is the building's wiring suitable for power line carrier, and how far is the furthest load. Church buildings often have additions from several decades, which affects both the electrical layout and the carrier signal path.

The proposal that comes out of that has an equipment list built specifically for your building.

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