Solar Panel Monthly Calendar: What to Do Each Month

Owning solar panels is mostly passive — but a handful of actions at the right time each month can make a meaningful difference to what you save and earn. This calendar gives you a practical checklist for every month, aligned with UK solar output patterns, Ofgem price cap cycles, and the legal restrictions that affect maintenance timing.

January — ~29 kWh/kWp

Output is near its lowest, but January is a useful planning month.

Review last year's total generation. Compare your annual figure against the MCS estimate on your installation certificate. If generation is more than 10% below estimate and the gap has widened year-on-year, it warrants investigation.

Annual tariff review. Many energy suppliers update standing charges and unit rates in January. Log into your supplier account and check whether your current tariff is still the best option — particularly if you have a battery, where time-of-use tariffs can significantly improve returns.

Archive generation data. Download and save the previous year's generation log from your inverter portal. Some portals only retain 12 months of data, and losing the historical record makes year-on-year comparisons impossible later.

February — ~38 kWh/kWp

Output is still low, but days are lengthening noticeably.

Ground-level inspection. From your garden or pavement, look across the roof for any storm damage from winter — cracked glass, displaced panels, loose flashing, or debris sitting on the array. Binoculars help. You are not looking for dirt at this stage, just structural issues.

Check the inverter error log. If your inverter's app or web portal shows historical fault codes, scroll back through the winter period. Overnight frost events occasionally trigger grid disconnect faults that resolve themselves but are worth logging.

Avoid drawing conclusions from February generation data alone — one clear cold week can make a mediocre month look excellent.

March — ~64 kWh/kWp

The spring equinox marks the start of the rapid output climb. March is one of the most action-rich months of the year.

Spring clean. Bird droppings accumulated from winter roosting are now worth removing. March cleaning — before peak season begins — maximises the benefit. Use water only, a soft cloth or long-handled brush, and avoid cleaning in direct sunlight (thermal shock risk to the glass).

Reconnect monitoring. If your inverter WiFi dropped over winter or you stopped checking the app, now is the time to reconnect and confirm data is transmitting correctly.

Get battery or diverter quotes. If you have been considering adding battery storage or a solar diverter to use surplus hot water, March is the ideal time to request quotes — before the spring installer rush drives waiting times up.

April — ~99 kWh/kWp

Shift appliances to solar hours. April is the first month where running your washing machine, dishwasher, or tumble dryer between 10am and 2pm makes a meaningful difference to self-consumption. Use delay-start or timer functions if you are not at home during those hours.

Check your SEG or export rate. Export tariff rates are sometimes updated in Q2. Log into your energy supplier's portal and confirm you are still on the best available export rate for your situation.

May — ~119 kWh/kWp (PEAK MONTH)

May is the UK's highest-output solar month. Not June. Not July. May.

The reason: days are nearly as long as midsummer, but temperatures are cooler. Solar panels lose efficiency in heat (approximately 0.35% per degree above 25°C), so the cooler May temperatures push output above what the warmer summer months achieve.

Maximise self-consumption. Run every high-draw appliance you can during solar hours. Set appliance timers the night before. If you have a smart plug or home energy system, check that automations are active.

Battery health check. If you have a battery, confirm it is cycling normally and check for any degradation warnings or error codes in the app.

Install a battery now if you haven't yet. If you are considering adding battery storage but have not yet committed, May is the optimal point. Installing in May captures this peak month and the two near-peak months that follow, rather than waiting until next spring.

June — ~115 kWh/kWp

Near-peak output, with export volumes high.

Consider a variable export tariff. If you are on a flat-rate SEG export tariff and exporting large volumes, it may be worth comparing against Agile Outgoing or similar variable-rate export options. On high-export days, variable rates can outperform flat rates — though they can also underperform on low-demand days.

Check panel ventilation. On hot days, confirm the gap beneath your panels is clear. Panels need airflow between the panel back and roof surface for cooling. If you have recently had roof work done, check that nothing is blocking the gap. MIS 3002 specifies a minimum 50–100mm clear gap.

July — ~114 kWh/kWp

Expect slightly lower efficiency on hot days. A 35°C summer day can push panel temperatures to 50–60°C. At those temperatures, efficiency drops by around 10% compared with standard test conditions. This is not a fault — it is expected physics. Output is still high; the panels are just not running at their theoretical maximum.

Inverter ventilation. Inverters also lose efficiency in heat. Check that your inverter is not in direct sunlight or a poorly ventilated location. If it is hot to the touch during peak generation hours, improving the ventilation around it is worthwhile.

August — ~101 kWh/kWp

Output is declining from midsummer but still strong.

Plan additions for next year. If you want to expand your system, add a battery, or install a diverter, August is a good month to start the planning process. MCS installers in popular areas can have 3–6 month waiting lists.

Get quotes while installers are quieter. August is typically less busy than spring for installation — you may find more flexibility on scheduling and, in some cases, more competitive quotes.

Bird proofing prep. If you noticed nesting activity under your panels in spring or summer, the installation window opens in September. Plan now so you can act promptly when it becomes legal to do so.

September — ~75 kWh/kWp

Output drops noticeably as days shorten.

Bird proofing installation window opens. From September through to February, it is legal to install bird proofing mesh under solar panels. Under the Wildlife and Countryside Act 1981, disturbing active nests between March and August is a criminal offence — so September is the earliest you can act on any nesting you observed over summer. Mesh costs approximately £50 per panel installed.

Switch to winter battery strategy. If you have a battery, the optimal strategy changes from summer to winter. In summer, the battery fills from solar surplus. In autumn and winter, the priority shifts to charging from a cheap overnight electricity rate (such as Octopus Go) and using that stored energy during dark evenings. Check your inverter's charge scheduling settings and update them.

October — ~47 kWh/kWp

Output is now below half of the May peak. On heavily overcast autumn days, your panels may produce very little. This is expected — do not mistake seasonality for a fault.

Confirm winter charging schedule. Make sure your battery's overnight charging is configured for the cheap-rate window on your tariff (for example, 00:30–05:30 on Octopus Go at 5.5p/kWh currently).

November — ~30 kWh/kWp

Winter is not zero output — clear November days can still generate meaningful energy — but generation is low enough that faults can go unnoticed.

Check monitoring is transmitting. Log into your inverter portal and confirm data is recording. A faulty panel or inverter string in November may not be obvious from bill savings alone — low generation blends in with the seasonal baseline.

Review home insulation. This is a tangential but important point: reducing your heating demand in winter is the most cost-effective complement to solar during the months when panels generate least. Loft insulation, draught-proofing, and smart thermostats all reduce the energy you need from the grid.

December — ~25 kWh/kWp

The lowest-output month of the year.

Year-end data download. Save your full year's generation data before portal logs roll over. Some inverter portals retain only 12 months of history — if you miss the window, the data is gone.

Plan upgrades for Q1. If you want to make changes next year — a new battery, additional panels, inverter upgrade — December is the time to start researching and requesting quotes. Good installers book up early in the spring.

Do not draw year-on-year comparisons from December data alone. Annual totals are the valid comparison; monthly figures are too affected by weather variation to be meaningful in isolation.

Calendar summary

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