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Solar and backup power in Cardiff

Cardiff, Wales, gets 2.94 peak sun hours a day on average. The dullest month is December at 0.62 hours, 88% less than June, the sunniest at 5.32. That makes it sunnier than 65% of the 24 cities we cover in the United Kingdom.

Peak sun hours a day, long-term monthly average. The blue bar is the month with least sun.

Sunshine in Cardiff is clearly below its yearly average for 5 months, from October to February. That stretch decides how many panels you need if solar has to keep up all year. Across the year, Cardiff gets 3% more sunshine than the average of the cities we cover in the United Kingdom.

What a home in Cardiff needs

Three example homes, each covering a 12-hour daily outage with a lithium battery and solar panels to recharge it. Panels are 450 W. The month-with-least-sun figure is what keeps you covered all year.

Home	Inverter	Battery	Panels, December	Panels, yearly average
Essentials 6 lights, 2 fans, a fridge, TV, Wi-Fi and phone charging	1 kW	2.6 kWh	10	3
Family home Essentials plus a freezer, more lights, a laptop, a desktop and a water pump	3 kW	7.4 kWh	29	6
With air conditioning The family home plus two small air conditioners for 6 hours a day	5 kW	14.9 kWh	57	13

December sunshine in Cardiff is weak, at 0.62 peak sun hours a day, so covering outages with solar alone that month needs a very large array. Most homes here size panels for spring to autumn and recharge batteries from the grid or a generator in the darkest weeks. Switch the calculator to "Yearly average" to see that size.

Your own appliances will differ. Put them into the calculator below, which already has Cardiff's sunshine.

Size your own system in Cardiff

1 Where is the system?

Sunshine for Cardiff, United Kingdom.

Peak sun hours a day

Month with least sun Yearly average

Using December, the month with least sun, so the plan works all year.

2 What should keep running?

Appliance	Watts each	How many	Hours a day	Remove
LED light bulb
Refrigerator / fridge
Wi-Fi router
Phone charger
TV, 32–43 inch
Ceiling fan
Laptop

Add an appliance

Watts are typical figures. The label on the appliance or its plug shows the real number: use that if you can.

3 Your power situation

Hours a day without grid powerUse 24 if there is no grid at all.

Battery type Lithium (LiFePO4) Lead-acid / tubular / AGM

Solar panels should Recharge the battery after outages Power everything, every day No solar, battery only

Panel size

Planning tips for Cardiff

Size panels for December, not for the yearly average. A system sized on the average falls short in the dullest weeks, which is when you most need it.
Dust, heat and shade cut output. Keep panels clean, leave air space under them, and avoid anything that shades them between mid-morning and mid-afternoon.
Ask installers for the inverter's continuous and surge ratings, the battery's usable capacity and chemistry, and the panels' total watts. Compare those numbers with your plan rather than the package name.

Guides for planning in Cardiff

Nearby cities

All cities in the United Kingdom

Sunshine: NASA POWER climatology, ALLSKY_SFC_SW_DWN, monthly averages for 25-year Meteorological and Solar Monthly & Annual Climatologies (January 2001 - December 2025), at 51.48, -3.18; retrieved 2026-11-09. Peak sun hours equal kWh of sunlight per square metre per day on flat ground; tilted panels usually collect a little more.