American utilities have replaced most residential electromechanical meters with advanced metering infrastructure. The new meter is a small embedded computer: it samples voltage and current thousands of times a second, accumulates energy into registers, drives an LCD, blinks an optical pulse output, and radios interval data back to the utility on a schedule. For most households none of that is interesting. For a Shabbat-observant household it raises a question that did not exist with a spinning-disc meter, because every change in household load is now measured by an electronic device and eventually reported.
Projects House works on this as an engineering problem for product developers, utilities, and institutions. We do not rule on halachic questions; those belong to a qualified posek, and observant households differ in the guidance they follow. What an engineering firm can contribute is an accurate description of what the meter actually does, and a set of design options that change the causal picture in ways a posek can evaluate.
What an AMI Meter Actually Does
It helps to separate the meter into four subsystems, because they behave very differently.
| Subsystem | Behavior | Driven by |
|---|---|---|
| Metrology front end | Samples line voltage and current continuously at a few kHz | Its own free-running clock; runs regardless of load |
| Energy registers | Accumulate integrated energy in memory | Continuous accumulation; value changes with consumption |
| Display and pulse LED | Cycles through readings; optical output blinks per unit of energy | The LED blink rate is directly proportional to instantaneous load |
| Communications | Transmits interval data on a fixed schedule, typically every 15 minutes or hourly | Scheduler, not events, in normal operation |
Two observations follow, and they matter more than any marketing claim.
First, the meter is already running. It does not wake up when a light is switched on. The analog-to-digital converters were sampling before, during, and after, at a rate set by a crystal, and the radio transmits on a calendar it keeps itself. In that respect the architecture resembles the continuous-scan pattern engineers deliberately design into other products for this market, described in grama and indirect-action mechanisms.
Second, the parts that are directly and immediately responsive to load are the optical pulse LED and, on some meters, the instantaneous-demand digits on the LCD. The pulse LED typically emits a defined number of flashes per kilowatt-hour, so switching on a load visibly and immediately increases the blink rate. That is the element most often raised in discussion, and it is also the element most easily addressed in hardware.
Options on the Meter Side
If you are designing or specifying meters, or working with a utility on an accommodation program, several things are within reach.
- Disable the optical pulse output. The pulse LED exists for field calibration and test benches, not for billing. Meters generally support disabling or masking it in configuration. This removes the most direct visible response to load.
- Freeze the display. A configured mode that stops the LCD from cycling and holds a fixed screen removes another directly changing element. The design considerations are the same as for any product display, including whether the panel needs a backlight at all.
- Strictly scheduled communications. Confirm that the meter is not configured for event-driven reporting: no push on threshold crossing, no last-gasp-style event uplinks except for genuine outage reporting, no on-demand reads scheduled during the period. Many meters support both modes and ship with event reporting enabled.
- No remote actuation during the period. Meters with a remote service switch, load-limiting relay, or demand-response contactor should have those functions locked out. This is a configuration and utility-process question as much as a firmware one.
- Documented interval behavior. Whatever the design is, it should be written down with measured evidence rather than asserted, in the form described in writing halachic requirements into a product spec.
Utilities across the country also run opt-out programs that let a customer retain a non-communicating meter, usually for a monthly fee in the range of a few dollars to twenty dollars plus a one-time charge. That is an administrative path rather than an engineering one, but it is worth knowing it exists before designing anything.
Options on the Customer Side of the Meter
The more interesting engineering happens downstream of the meter, in the home or building, where a product developer actually has design freedom.
Constant-load regulation
The concept: hold total household draw approximately constant during the period so that switching an individual load does not change what the meter sees. A controlled ballast load, typically a resistive element in a safe, thermally managed enclosure such as a water heater or a dedicated heating element, is modulated inversely to the rest of the house. When a light turns off, the ballast absorbs the difference.
Engineering reality check: this only works if the ballast has enough headroom to cover the largest load that might switch, which means a significant continuous draw and real wasted energy. The control loop also has to respond, and its response is caused by the load change, which shifts the question rather than removing it. It is genuinely useful in narrow cases and oversold in broad ones. Anything operating at line voltage in a residence has to satisfy the safety design rules covered in mains-powered product design and be listed to the applicable UL standard.
Battery islanding
A cleaner architecture for many buildings: charge a battery system before the period, then run some or all of the building's circuits from that battery, disconnected from the grid, for the duration. Household load changes then never reach the meter at all, because there is no metered current flowing. The transfer itself happens once, on a schedule, before the period begins.
This has become practical because residential storage is now a mainstream product. The design work is sizing: a typical observant household's Shabbat load, including refrigeration, lighting on timers, hot water, and HVAC, can run anywhere from 15 to 60 kWh over a full period, which is one to several battery cabinets. Sizing, thermal management, and cell selection follow ordinary battery pack design practice at a much larger scale, plus the transfer switch, islanding controls, and interconnection approval from the utility.
Scheduling the loads themselves
The oldest and still the most widely used approach is not to change the meter but to remove the need to switch anything: loads run on schedules set before the period. That is the entire premise of Shabbat timers and time controllers, and it extends naturally into climate control through Sabbath mode thermostats and HVAC controls. A house where nothing is switched by a person has no meter question to answer.
Institutional Buildings
Hospitals, hotels, senior living communities, and schools serving observant populations face the same question on a commercial meter, with two differences. Commercial metering often includes demand charges based on peak intervals, which makes constant-load schemes expensive rather than merely wasteful. And these buildings usually already have a building management system, a generator, and sometimes storage, which makes islanding or scheduled-load approaches easier to implement than in a single-family home. Integration with the existing BMS is the real project, and it looks much like the work described in Shabbat technology for hotels and institutions.
What to Build and What to Document
If you are developing a product in this space, the deliverable that decides the outcome is not the hardware. It is a clear causal account: what the meter samples and when, what the product changes and when, which paths are event-driven and which are scheduled, and measured evidence for each claim. Bring that to a qualified posek and the review can proceed on facts. Bring a brochure and it cannot.
Projects House designs energy hardware and controls, including load management, storage integration, and metering-adjacent products, and prepares the technical documentation these reviews require. Tell us what you are building through our contact form.