Glossary
The terms, defined plainly.
Solar monitoring and AI sales both come with vocabulary that hides more than it explains. These are the words that matter, in plain language, with no assumed knowledge.
- String-level monitoring
- Monitoring that reports the output of each individual string of solar panels rather than only the system total. It matters because a system with one dead string still reports plausible-looking total production, so a failure can persist for months without triggering any alarm. Catching it requires comparing each string against what it should be producing, not against zero.
- Digital twin
- A software model of a physical solar system that predicts what it should be producing under current conditions, so actual output can be compared against expectation rather than against nothing. The comparison is what converts raw telemetry into a judgement about whether a system is healthy.
- Weather-adjusted baseline
- The output a solar system should be producing right now given the irradiance, temperature and cloud cover at its location. Comparing against a weather-adjusted baseline is what separates a real fault from a cloudy afternoon — without it, every overcast day looks like a problem and every gradual failure looks like weather.
- Performance ratio
- The ratio of a solar system's actual output to the output its installed capacity should have produced under the conditions it experienced, expressed as a percentage. A healthy residential system typically sits in the high seventies to mid eighties; a sustained drop indicates soiling, shading, degradation or a failed component.
- Weather-corrected performance ratio
- A version of the performance ratio that adjusts the expected output for the cell temperature the system actually saw, so the figure does not swing with the seasons. A plain performance ratio tends to read higher in cool months and lower in hot ones even when nothing is wrong; correcting for temperature removes most of that swing. NREL published a method for it in 2013 (Weather-Corrected Performance Ratio, NREL/TP-5200-57991), intended for use in performance tests and guarantees.
- Solar fleet monitoring
- Watching many solar systems at once — tens to thousands, often on different inverter brands — from one place, instead of opening each system in its maker's app. The useful version does more than show which systems are online: it compares each system's output with what it should have made, and puts the ones losing the most at the top. It is used by installers, O&M companies, asset owners and lenders.
- Expected vs actual energy
- The gap between what a solar system should have produced over a period, given its size, layout and the weather it actually saw, and what its meter or inverter says it produced. Expected energy comes from a model; actual energy comes from the data. The difference, in kWh and in money, is the basic measure of underperformance, because it catches faults that never raise an alarm.
- Availability
- The share of time a solar system or piece of equipment was able to produce power, usually counted only during daylight hours. An inverter that was down for one full day in a thirty-day month has an availability of a little under 97% for that month. O&M contracts often promise a minimum availability, and they define carefully which outages count — grid outages and planned maintenance are commonly excluded.
- Specific yield
- The energy a solar system produced over a period divided by its DC size, written as kWh per kWp (kilowatt-hours per kilowatt-peak). It lets you compare systems of different sizes: two similar systems in the same town should have similar specific yields, so one that sits well below its neighbours is worth a look. Annual specific yield depends heavily on location, tilt and shading.
- Clipping
- What happens when the solar panels could deliver more power than the inverter is rated to output: the inverter holds its output at its limit and the extra is lost. Designers often accept some clipping on purpose by sizing the panels larger than the inverter, because it raises output in the morning, evening and on cloudy days. Clipping shows up as a flat top on the daily production curve on sunny days, and it should not be mistaken for a fault.
- Inverter communications loss
- When an inverter stops sending data to its monitoring cloud. The cause is often the home's Wi-Fi, a router change, a failed cellular link or a data logger, and the system may still be producing normally. But you cannot tell from the outside, so a system that has gone quiet has to be treated as unknown until it reports again — and a long silence can hide a real outage.
- Ground fault (insulation fault)
- A fault where current can leak from the solar wiring to earth, usually because damaged cable, water in a connector or a cracked panel has lowered the insulation resistance. Inverters check insulation resistance before they connect and will refuse to start, or shut down, if it is too low — often shown as an "ISO" or "Riso" error. It is a safety issue as well as a production loss, and it needs a technician on site to find.
- O&M SLA
- The service-level agreement in an operations-and-maintenance contract: the promises an O&M provider makes to the system owner, and how they are measured. Typical terms cover how fast the provider responds to a fault, how fast it must be fixed, minimum availability, and the reports the owner receives. An SLA is only as good as the evidence behind it, which is why owners ask for proof that production actually recovered after each repair.
- Speed-to-lead
- The elapsed time between a prospective customer making contact and receiving a first substantive response. It is one of the strongest predictors of conversion in inbound sales because prospects contact several companies at once and engage with whoever answers first. Our own median first response is 23 seconds, measured across 4,019 intervals.
- Orphaned solar system
- A solar installation whose original installer has gone out of business, leaving the homeowner with no one responsible for monitoring, warranty administration or repair. The hardware keeps producing, but nobody is comparing its output against expectation, so faults accumulate silently. Any monitoring platform that can reach the inverter brand through its cloud API can adopt these systems without a site visit.
- Solar Assurance plan
- A recurring subscription an installer sells to a homeowner covering ongoing monitoring, fault alerts and periodic performance reporting on a system already installed — also called a care plan. US installers commonly price these between $10 and $25 per month, and they convert an install base that is already paid for into recurring revenue.
- Truck roll
- A dispatched site visit: a technician and a vehicle sent to a property to diagnose or repair a solar system. It is the largest variable cost in solar service work, which is why identifying a fault remotely first matters — a visit made with the problem already known is billable work rather than an unpaid investigation. In a monitoring-led service model the installer bills the truck roll and the repair at their own rates.
- TCPA consent
- Permission a US consumer must give before a business may contact them by automated text or call, under the Telephone Consumer Protection Act. Compliant systems capture the consent, record when and how it was given, honour quiet hours and opt-outs, and keep an audit trail — the trail matters because the burden of proving consent falls on the sender.
- 10DLC
- The US carrier framework for sending application-to-person text messages over standard ten-digit long codes. Businesses register their brand and each messaging campaign with the carriers before sending; unregistered traffic is filtered or blocked. Registration is why an SMS product cannot simply be switched on for a new customer on day one.
- Inverter API
- The cloud interface an inverter manufacturer provides for reading data from systems using its hardware, usually authenticated with an account credential or OAuth token. Reading a fleet through these APIs requires no additional on-site hardware, because the inverter is already sending its data to the manufacturer's platform.
- kWh vs kW
- A kilowatt (kW) is a rate of power at an instant; a kilowatt-hour (kWh) is an amount of energy over time. A 10 kW system produces 10 kW at peak but perhaps 40 kWh across a day. System size is quoted in kW, electricity bills are charged in kWh, and confusing the two is the most common error in solar arithmetic.
- Net metering
- A billing arrangement in which a solar owner exports surplus generation to the grid and receives a credit against electricity drawn later. The value of that credit varies by jurisdiction and utility, and changes to net-metering rules are among the largest single influences on residential solar economics.
- Soiling
- Accumulated dust, pollen, salt or bird droppings on panel surfaces, reducing the light reaching the cells. Soiling losses build gradually and reverse after rain or cleaning, which is what distinguishes them from a hardware fault: the pattern is a slow decline followed by a sharp recovery.
- Degradation
- The gradual, permanent decline in a solar panel's output as it ages, typically a fraction of a percent per year and warrantied by manufacturers over twenty-five years. Because it is slow and expected, degradation should be modelled and subtracted before judging performance — otherwise a healthy older system reads as underperforming.
- Guardrails for AI
- Hard-coded constraints applied to an AI agent's output before it is sent, defining what it may not say or offer regardless of how a conversation develops. In sales the practical purpose is protecting price: our guardrail layer logged 1,630 interventions in five weeks, rewrote 49% of outgoing messages, and blocked 196 absolute price leaks.