Solar monitoring and maintenance

Keep the commissioning baseline

The handover pack is the starting point for later monitoring and maintenance. Keep:

• array plan and roof photographs
• string and MPPT allocation
• inverter, module and optimiser details
• electrical schematic
• commissioning test results
• DNO record
• meter and CT positions
• meter serial numbers and opening readings
• inverter and monitoring account
• original settings and firmware
• warranties and maintenance instructions

After the first few complete days of operation, photograph the normal monitoring screens. Include the direction of grid flow, reported PV generation and any battery or household-consumption values. This helps identify a reversed sensor or changed display later.

Retain the installer’s contact and the route for transferring monitoring to another installer. The owner should hold administrator access rather than depend on the original company’s account.

Inverter, portal and settlement-meter boundaries

Solar monitoring can display several figures that should not be compared as though they were the same meter.

• inverter or portal generation may be measured or derived on the DC or AC side, depending on the product
• portal consumption may be calculated from inverter and grid-sensor data rather than measured directly
• grid import is electricity entering through the settlement meter
• grid export is electricity leaving through the settlement meter
• FIT generation is measured at the approved generation-meter boundary
• battery charge and discharge may be measured on the AC or DC side

For a simple PV-only system using AC generation, grid import and grid export from the same interval, household consumption can be derived as:

consumption = AC PV generation + grid import − grid export

If the grid CT (current transformer) is reversed, assigned to the wrong phase or placed around the wrong conductor, the derived figure can be wrong even while the inverter’s own generation value is reasonable.

Grid export excludes electricity used on site before the settlement meter. A smart-meter export total should not be used as though it were total PV production.

A battery or another source needs the additional charge, discharge or generation terms defined by the installed metering model. Energy may cross an inverter or meter more than once and each conversion loses some energy. Use the installed schematic and portal definition to identify the measurement boundary before applying an equation.

Inverter status, portal outages and local faults

A routine owner check can cover:

• current inverter state
• active warning or fault
• recent generation graph
• gaps in portal data
• smart-meter import and export direction
• visible damage from ground level
• unusual noise, smell or heat around accessible equipment

Do not open electrical enclosures or operate an unfamiliar DC isolator to investigate. PV strings can remain live in daylight after the AC supply is isolated.

If the portal is blank, separate a communications problem from a generation fault:

1. Check whether the app or web service reports an outage.
2. Check the inverter’s local display or status indicator without opening equipment.
3. Confirm whether the home internet or monitoring gateway is connected.
4. Look for recent smart-meter export where export would normally be expected.
5. Record the time, status and fault code for the installer.

An inverter can continue to generate during a cloud or internet outage. It can also be online while reporting a genuine array or grid fault. Use the inverter’s local status, settlement-meter data and fault record to distinguish a portal outage from a generation fault.

Use generation data as a trend

Daily solar generation varies with irradiance, temperature, cloud, shade, snow and household control. Comparing one bright spring day with a hazy summer day is not a reliable performance test.

Use:

• similar periods from different years
• nearby weather or irradiance context
• separate roof planes where monitoring supports it
• expected seasonal shape
• inverter event history
• changes in shade or soiling

The original MCS estimate is an annual design comparison. It is not a guarantee for one year’s weather and usually does not predict each day or half-hour.

Sustained underperformance means a pattern that remains after obvious weather and data-boundary differences have been considered. Useful evidence for the installer includes dates, graphs, fault codes, weather context and any physical event such as roof work.

Do not convert a shortfall into a specific failed component without electrical testing. A lower graph can result from shade growth, a string fault, inverter derating, grid voltage, export limitation, dirty modules, communications gaps or a changed setting.

Inverter warnings and fault records

Save the exact code and wording before restarting equipment. Include:

• date and time
• weather
• whether the fault clears
• grid import or export at the time
• recent electrical or building work
• app and inverter firmware

Manufacturer instructions determine which owner actions are permitted. A documented restart may be appropriate for some communications faults. Repeated protective-device operation, burning smell, water ingress, arcing noise or damaged cabling requires isolation by a competent person and should not be repeatedly reset.

Grid-related events can be intermittent. If the inverter records voltage or frequency faults, the installer can compare the installation, settings and supply data. Do not change statutory grid-protection settings from an online suggestion.

For a multi-string or module-level system, preserve the per-string or per-module evidence before software, inverter or optimiser replacement. Missing data in one tile can be a communications issue rather than a failed module.

Cleaning decisions

Rain removes some loose dirt from a suitably pitched array, but local conditions vary. Bird deposits, lichen, traffic residue, salt, dust and shallow roof pitch can change the result.

There is no universal annual cleaning requirement or loss percentage for every UK roof. Use:

• safe ground-level inspection
• local opaque deposits
• a repeatable performance pattern
• the module manufacturer’s instructions
• the cost and access risk

A small unproven energy gain may not justify roof access. Work at height needs appropriate planning, equipment and competence. Live PV DC cabling and connectors add electrical risk around the array.

Where cleaning is justified, the contractor should follow the module instructions for water, tools, detergent, pressure and temperature. Abrasive tools or thermal shock can damage glass or coatings and may affect warranty.

Cleaning cannot repair an electrical fault, failed bypass path, cracked module or water-damaged connector. If a local deposit has caused persistent heating or visible damage, arrange a technical inspection.

Roof, mounting and cable observations

Inspect from ground level or another safe location after severe weather and before or after unrelated roof work. Look for:

• visibly displaced or damaged modules
• loose external conduit
• sagging cable
• debris accumulated beneath an array
• roof-covering movement
• signs of water entry inside the building
• bird or pest activity
• new vegetation shade

Do not walk on modules or remove mesh, clamps and flashings. A defect can involve both the weathering and the electrical system.

Tell roofers that the array remains electrical generation equipment in daylight. Removal, temporary storage and reinstatement should be planned with a competent PV contractor. Keep an updated layout and test record after any work.

If access equipment is already erected for another job, it may be sensible to coordinate a competent array and roof inspection. The electrical and structural scope should still be agreed rather than assumed to be included.

Professional inspection and testing

Domestic PV does not have one universal annual service interval. Inspection frequency should be appropriate to the installation, connected AC system, environment, manufacturer requirements and observed condition.

Earlier inspection can be justified by:

• repeated inverter or protection faults
• visible damage or water ingress
• sustained unexplained loss of performance
• severe wind, impact, fire or flooding
• roof work or building alteration
• cable disturbance
• change to a battery, inverter or consumer unit
• an insurer, warranty or commercial requirement

Agree the scope. It may include visual inspection, mounting and cable checks, labels, protective devices, isolation, electrical tests, inverter logs, monitoring sensors and comparison with commissioning results.

A generic “solar service” label does not state whether roof access, DC testing, thermal imaging, firmware, cleaning or electrical remedial work is included.

The report should record observations, measurements, limitations and recommended actions. Keep it with the commissioning pack rather than accepting only a verbal statement that the system is fine.

Isolators and protective equipment

DC switch-disconnectors operate under different conditions from ordinary AC switches. Selection, configuration and maintenance follow the installed design and manufacturer instructions.

An owner should know the emergency isolation points and labels explained at handover. Routine operation of isolators is not a substitute for maintenance and an unfamiliar switch should not be used as a diagnostic tool.

Heat, discolouration, cracking, water ingress, loose mounting or a smell around an isolator or connector needs competent attention. Do not remove a cover while the PV array can energise the circuit.

AC protective devices, surge protection and the consumer unit also form part of the system. Their inspection is coordinated with the electrical installation rather than treated as an isolated panel check.

Generation meters and FIT records

Legacy FIT payments use the accredited installation and approved generation-meter record. Preserve:

• generation-meter serial number
• periodic readings and submitted evidence
• photographs showing meter and reading
• replacement record
• old and new serial numbers
• final old reading and opening new reading
• FIT licensee approval or correspondence

Do not discard a failed or replaced meter until the required record has been agreed. A gap in the audit trail can affect payment evidence.

Battery or inverter work should preserve accurate measurement of eligible generation and export. Keep the revised schematic and notify the FIT licensee in line with its current guidance.

For SEG, payment uses actual export-meter readings under the supplier contract. The inverter portal is not a substitute for settlement export data.

Monitoring services and account continuity

Cloud monitoring can change independently of the installed hardware. A manufacturer or operator may alter its app, subscription, API or support model.

The practical differences between monitoring services include:

• free and paid features
• local display or local data
• cloud dependency
• data export
• administrator transfer
• installer access
• behaviour after internet loss
• supported firmware and gateway

A long equipment warranty does not guarantee that every cloud feature will remain free for the same period. Keep local serial numbers, settings and commissioning evidence outside the portal.

When changing the router, mobile phone or account email, confirm that alerts and historic data remain available. Do not give a service company the only administrator login.

Solar maintenance records

Keep one dated log containing:

• generation and fault observations
• cleaning
• roof or building work
• electrical inspection and test
• inverter, optimiser or module replacement
• firmware and setting changes
• meter replacement
• DNO, FIT or SEG correspondence
• warranty claims

Record the reason for work and the before-and-after equipment or setting. This makes later faults easier to trace and supports a property sale.

The records should distinguish an owner observation from a professional inspection. A clear ground-level photograph can be useful evidence, but it does not certify the roof fixing or electrical condition.