Core concepts
The terms DUET uses for your sites, their performance, and the problems that affect them.
DUET models what your solar and battery sites should produce, compares that with what they actually produce, and explains the difference. The same terms appear in the DUET app, in reports, in the MCP connector, and in the Platform API.
Organizations, portfolios, and sites
- An organization is your company's account in DUET. Every user, site, and API token belongs to one organization.
- A portfolio is a named group of sites within an organization, for example all sites in one region or under one owner.
- A site is one monitored plant. The Platform API calls a site a project, and identifies it by its project ID.
You see only the organizations, portfolios, and sites that your DUET account has access to. The MCP connector and the Platform API follow the same access rules.
Devices
Each site is modeled as a hierarchy of devices:
- Meter: the point where the site connects to the grid.
- Blocks: sections of the site, each with its own power conversion equipment.
- Inverters: the devices within each block that convert DC power to AC power.
- Combiners, MPPTs, and trackers: the equipment below each inverter, where the site reports it.
Each device has a hierarchy ID that is unique within its site. Weather stations and irradiance sensors report alongside the devices.
Measured and expected energy
- Measured energy is what the site's meter or inverters reported.
- Expected energy is what DUET's physics model says the equipment should have produced under the weather the site measured. When a power limit is active at the site, expected energy is capped at that limit.
DUET models every site at 15-minute resolution, from the whole site down to individual inverters.
Performance index
The performance index (PI) is measured energy divided by expected energy. A PI of 1.00 means the equipment produced what the model expected. A PI of 0.95 means it produced 5% less.
Energy basis
Measured energy at the meter can come from two sources, which can differ by a few percent:
- Meter: the total of the meter's power readings over time.
- Totalizer: the meter's own running energy count.
Reports and API responses state which basis a figure uses.
Losses
DUET splits the gap between expected and measured energy into losses, each labeled with its cause. Common causes include inverter outages and trips, combiner outages, clipping, soiling, snow, stuck trackers, and lost communication.
- Investigate groups losses that DUET couldn't attribute to a cause. A large Investigate share means someone needs to look at the site.
- Gain is energy produced above expectation. Net loss is gross loss minus gain.
- Grid curtailment is energy the grid operator told the site not to produce. DUET reports it separately from losses, because it isn't a fault at the site.
Availability
Availability is the share of daylight hours, weighted by capacity, in which a site's inverters were available to produce. It runs from 0 to 1 and follows IEC TS 63019. Battery sites report availability for each battery container.
Issues, work orders, and alarms
- An issue tracks a problem on one or more devices. It has a status, a priority, a cause, and the energy it lost over the time it was active.
- A work order is a field job raised against an issue, with an assignee, a due date, and a log of the work done.
- An alarm is an event reported by the site's equipment or monitoring system, such as an inverter fault. An alarm is raised, can be updated, and is resolved.
Your systems can receive changes to all three as webhooks.
Data health
Missing or stale data is the most common reason a site looks worse than it is. Check data health before you investigate a drop in performance.
- Data freshness is how recently a site last reported.
- Data quality scores each sensor channel on completeness, valid ranges, and stuck values.
- Satellite irradiance days are days when a site's own irradiance sensors were missing or unreliable, so DUET calculated expected energy from a satellite irradiance estimate. Results on those days are less certain.
- Omitted days are days left out of reporting, usually because of data problems. They don't count against performance.
Time and units
- Timestamps are in the site's local time unless a field says UTC.
- Energy is in watt-hours (Wh) and power in watts (W) unless a field or label says otherwise, for example MWh.
- PI and availability are fractions, such as 0.97, not percentages.