When solar panels are not generating enough electricity, the complaint is usually won or lost on evidence. The installer, lender or dispute scheme needs to see what was promised, what the system actually produced, and what has already been done to investigate the difference.
This guide is for homeowners preparing a formal complaint about low solar generation. Equisure Direct does not survey roofs, inspect solar systems or repair equipment. It prepares complaint and dispute correspondence from the customer’s paperwork.
Start with the shortfall, not the suspected cause
Low generation can happen for several reasons. Some are ordinary, such as winter weather, shading at particular times of day, temporary dirt, household usage patterns or changes in monitoring. Others may point to a sales or installation problem, such as a poor design, missing handover, incorrect settings, inverter faults or a forecast that did not match the property.
The first letter should not guess the cause. It should show the shortfall.
Write down:
- the generation figure you were told to expect;
- where that figure came from, such as a quote, proposal or savings estimate;
- the generation actually recorded by the app, meter or inverter;
- the period compared, such as one month, three months or twelve months;
- whether the issue started immediately after installation or later.
For example, a complaint that says “the proposal forecast X kWh per year, but the app and generation meter show Y kWh over the first twelve months” is clearer than a complaint that only says the panels are poor.
Gather the generation data
Useful generation evidence includes:
- app screenshots for daily, monthly and annual output;
- generation meter photographs;
- inverter export files, where available;
- electricity bills before and after installation;
- export payment statements, if you have them;
- dates of any outages or inverter warnings;
- screenshots showing panels, inverter and battery status at the same time.
Keep screenshots with the phone or computer date visible where possible. If the app lets you download data, save the raw file as well as the screenshots. Do not edit the screenshots beyond cropping personal information if you need to share them.
Compare like with like
A common problem is comparing a sales forecast for a year with only a few winter weeks of generation. That will usually weaken the complaint. The better comparison is:
- the forecast period against the same length of real data;
- annual forecast against a full year where available;
- monthly forecast against monthly app records;
- quoted savings against bills over the same season.
If only a short period is available, say that clearly. The letter can still ask the installer to explain the early shortfall, but it should not overstate what a few weeks of data proves.
Find the sales and design paperwork
Low generation complaints usually need the sales file. Gather:
- quote or proposal;
- system size in kWp;
- number and type of panels;
- inverter make and model;
- battery information, if fitted;
- roof plan or design;
- shade assessment, if supplied;
- generation forecast;
- savings calculation;
- finance agreement, if finance was arranged;
- handover pack and final invoice.
MCS publishes consumer information at mcscertified.com. If your installation was MCS certified, the certificate and handover pack are important because they help identify the installer, system and commissioning paperwork. If those documents are missing, include that in the complaint.
Check whether a fault has already been reported
Before writing the formal complaint, make a timeline:
- installation date;
- handover date;
- date the low generation was first noticed;
- screenshots or readings from that date;
- dates you contacted the installer;
- any remote checks or engineer visits;
- what the installer said;
- what remains unresolved.
If the installer visited or changed settings, ask for the visit notes. If the installer says output is normal, ask them to explain that in writing against the sales forecast and the recorded generation.
Decide whether the complaint is about installation, sales or finance
The recipient depends on the evidence.
If the system is underperforming because of a possible installation, commissioning, handover or equipment issue, start with the installer.
If the main problem is that the system was sold on a forecast or savings figure that now appears unrealistic, the complaint may be about the sales presentation as well as performance. In that case, ask the installer to identify the basis for the forecast and the assumptions used.
If the system was bought using installer-arranged finance or a credit card, a separate lender complaint may be relevant. The Financial Ombudsman Service says consumers should complain to the financial business first and keep the evidence and correspondence. If the financial business sends a final response, or the relevant time has passed, the complaint may then be referred to the ombudsman. See financial-ombudsman.org.uk/consumers/how-to-complain.
If you think the sales conduct was unfair or misleading, Citizens Advice explains how consumer issues can be reported to Trading Standards. That route is separate from your own complaint letter and does not replace writing to the installer or lender. See citizensadvice.org.uk/consumer/get-more-help/report-to-trading-standards/.
What to ask for in the complaint
The request should match the evidence. Depending on the facts, you might ask the installer to:
- explain the shortfall against the sales forecast;
- provide the generation calculation and assumptions;
- inspect or remotely check the system;
- provide missing handover and certification documents;
- confirm whether shading, inverter settings or commissioning issues were considered;
- provide a written outcome that can be used for scheme or lender escalation.
Avoid asking for everything at once. A focused letter is easier to answer and easier to escalate if the response does not address the evidence.
When to get independent evidence
If the installer denies there is a problem, an independent inspection or electrician report may help. Equisure does not provide that inspection. If you do obtain one, keep the report factual and attach it to the complaint. The strongest reports explain what was checked, what was found, and how that finding relates to the promised output or system design.
Quick evidence checklist
- Quote, proposal and generation forecast.
- App screenshots showing real output.
- Generation meter and inverter readings.
- Bills and export statements.
- Handover pack, MCS certificate and warranty papers.
- Installer messages and visit notes.
- Timeline of faults, warnings and contact attempts.
- Finance or credit card paperwork, if relevant.
- Any independent inspection or electrician report.
The aim is to make the shortfall easy to understand. Once the forecast, actual generation, paperwork and contact history are in one place, the formal complaint can ask for a specific written response rather than a general promise to look into it.
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