Why is my business electricity bill still high after solar? A working PV system can reduce grid imports without removing the whole bill. Start by comparing what the panels generated with what the business still bought, rather than assuming a fault.
For a factory, holiday park or larger rural site, the useful question is how generation, site use and the supply contract fit together. Separating those figures helps show whether you have a billing query, an operating-hours mismatch or a possible PV performance issue.
A generation figure is not a bill saving
Your solar app’s generation total measures electricity produced, not the amount you avoided buying. Commercial solar self-consumption means using that electricity on site rather than exporting it.
A site can use most of its solar output and still import heavily because its overall demand is much larger. Equally, substantial generation can coincide with low self-consumption if the site is quiet while the panels are producing.
If your dashboard shows a percentage, check whether it refers to the share of generation used on site or the share of site demand met by solar.
Your grid electricity bill concerns imports and your supply contract charges, not total solar production. Solar does not automatically cancel every imported unit or every charge. Check energy in kilowatt-hours (kWh) first, then the money charged for it.
Compare generation, use, export and imports over the same dates
To compare solar PV generation versus grid import, start with one invoice period. Match its opening and closing dates to the generation and export records, and check whether the billed readings are actual or estimated. Do not compare a calendar-month dashboard with an invoice covering different dates.
Separate the records into four measures, noting any you cannot verify:
- PV generation is the electricity the system produced during the period.
- Solar used on site is the part of that generation supplying the business rather than leaving as export. It is not the same as total site consumption.
- Export is the electricity sent out to the grid rather than used by the site.
- Grid import is the electricity still bought through the supply meter, which needs checking against the invoice.
If monitoring only records generation, do not assume it also measures import or export. A live kilowatt (kW) reading is not a period’s kWh total.
On a multi-building site, confirm which metered supply the PV serves. A generation report from one building should not be used to explain an invoice for a separate supply. If the layout is unclear, check the handover records or ask the contractor to clarify it.
For a simple site without batteries or other generation, subtracting export from generation gives an approximate figure for solar used on site. Adding grid import then indicates total site use. With storage or more complex metering, ask for a reconciled energy breakdown instead.
Monthly totals alone can hide midday exports and evening imports. Even if monthly generation matches monthly demand, the business can still import whenever demand exceeds output. Use time-of-day readings, where available, to see whether output coincides with demand.
Why commercial bills can remain high
Operating hours and seasonal demand
A factory adding an evening shift can buy more grid electricity even while its solar output is normal. A holiday park may export during a quiet afternoon, then import when guests return and demand rises. These are usage patterns, not proof of panel faults.
Review your electricity use profile for changes in occupancy, opening hours and equipment. Solar output is seasonal too: a winter period should not be judged against summer generation. Even year-on-year comparisons need weather and operational context.
Your non-domestic supply contract
First ask whether imported kWh has fallen. If it has but the bill has not, compare the unit rates and standing charges for each period, and separate any billing adjustments from current consumption. Other contracted charges may not move in step with solar output.
The relevant terms are in your non-domestic supply agreement. If an estimated bill does not match the available records, ask the supplier how it will be reconciled. Your supplier or energy adviser can clarify contract rates and billing adjustments.
Check export payments separately
Commercial solar export payments are separate from the value of using electricity on site. Ofgem’s Smart Export Guarantee guidance explains that some suppliers must pay eligible small-scale generators for exported low-carbon electricity. Eligibility and payment terms should not be assumed for every commercial installation.
Do not value exported kWh at the import unit price unless your actual agreement supports that assumption.
Check who pays for your exports, the meter readings used, the agreed rate and the payment period. Do not assume export income will appear as a credit on the import bill. A missing payment needs checking against the export agreement; it is not, by itself, evidence of lost generation.
If no export arrangement can be found, ask the relevant supplier what applies to the installation before counting on income.
When the evidence points to a PV performance issue
Commercial solar performance monitoring is useful when readings are compared with a suitable baseline, not judged from one low period. Look for a sustained, unexplained drop against the system’s expected seasonal output, or recurring system alerts. Check data gaps before treating them as zero generation.
Use the generation forecast from the original proposal, where available, and the system’s own past records. Check whether the forecast is annual or broken down by month; do not divide an annual estimate into equal monthly targets.
If that information is missing, ask a competent solar contractor what comparison is reasonable. A forecast is a comparison point, not proof that a shortfall is an equipment fault.
If output remains unexpectedly low after allowing for season, weather and monitoring context, a technical review through our solar maintenance services may be appropriate. The aim is to establish whether there is underperformance and what further investigation is justified, not to assume a component needs replacing.
Keep your own checks to invoices, records and monitoring information. Do not open electrical equipment, test circuits or reset protection to investigate a bill.
Gather the records for your supplier or solar contractor
A short, matched set of records is more useful than an invoice total alone. Gather:
- Import invoices, meter identifiers, reading dates and details of estimated readings.
- Generation and export records covering those same dates, plus export payment statements.
- The original generation forecast and handover information, if available.
- Opening hours, occupancy changes, extra shifts and recently added equipment.
- Monitoring alerts, data gaps and the dates of any known outages.
Contact the relevant supplier or energy adviser for rates, estimated bills and payment discrepancies. Contact a solar contractor for a persistent output shortfall or recurring PV alerts. Where records conflict, agree the meter and date range before deciding which explanation fits.
For help with a suspected system issue, speak to Maenporth Electrical Ltd about our solar PV services. Based at Maenporth, we serve Falmouth, Penryn and wider Cornwall. Call 01326 250297 to discuss the next step.