Autonomy scoreLocal analysis
Cardiff Home autonomy potential in Cardiff (Wales)
The strongest asset here is Food growing. It is not, however, what pays your home the most: that is Low-carbon heating.
Annual potential, standard home
£4,372
Four items added up — each one is a separate decision, in whatever order suits you.
Overall score
61 /100
Advanced
Cardiff: 61/100 achievable autonomy with a recommended setup.
Strong potential — high self-sufficiency in energy, water & food is well within reach.
What you could reach in Cardiff
A typical home in Cardiff can reach about 61% self-sufficiency with a right-sized solar, storage, rainwater and low-carbon heating setup — much of it backed by UK grants and 0% VAT. The figure sharpens once you enter your own home.
- ≈211 days a year off the grid — keep the fridge, lights, router and heating pump running straight from your own roof and battery, right through a winter outage.
- Rainwater self-reliance — ≈82,110 L harvested from a 100 m² roof covers the garden and toilet flushing, so hosepipe bans stop mattering.
- A real harvest — ≈295 kg of fresh vegetables over a ≈256-day frost-free season takes a genuine bite out of the weekly shop.
- A warm, low-bill winter — insulation plus a right-sized heat pump turns the local climate into low-carbon comfort and shields you from gas-price spikes.
From the most to the least profitable, here
What you could gain
-
Low-carbon heating51/100
~£2,471/yr
less heating after insulation + heat pump (−8,550 kWh/yr on 90 m², electric heating)
The detail
Realistic outlook
2,720 heating-degree-days: a high-efficiency heat pump is the lowest-carbon way to keep Cardiff warm.
Watch-outs
A heat pump only pays off in a well-insulated envelope — insulate first, then size the unit.
Grants & tips
Boiler Upgrade Scheme: £7,500 towards an air-source heat pump (England & Wales); ECO4 and the Great British Insulation Scheme fund insulation, plus 0% VAT on heat pumps.
Heating-degree-days (base 18°C) : ≈ 2,720 HDD — Source: PVGIS, hourly ERA5 temperatures 2005–2015 (base 18°C).
-
Food growing69/100
~£867/yr
off the weekly shop — up to ≈295 kg/yr of fresh vegetables from 100 m²
The detail
Realistic outlook
With about 256 frost-free days, a household garden in Cardiff supports two planting rotations a year.
Watch-outs
A productive garden needs space, decent soil and a few hours a week — start small and scale up.
Grants & tips
Council allotments (Allotments Act) give cheap growing plots; RHS and community-garden schemes support home food production.
Frost-free growing season : ≈ 256 days — Source: PVGIS, hourly ERA5 temperatures 2005–2015 (frost dates).
-
Solar energy57/100
~£774/yr
less electricity with 3 kWp on your roof (≈3,096 kWh/yr)
The detail
Realistic outlook
At 1,032 kWh/kWp per year, Cardiff offers solid potential for residential rooftop solar.
Watch-outs
Roof orientation, shading and DNO connection rules affect real output — get an MCS-certified site assessment first.
Grants & tips
Smart Export Guarantee (SEG): your supplier pays for surplus solar exported to the grid, plus 0% VAT on residential solar PV and battery storage until 2027.
Annual PV yield : 1,032 kWh/kWp — Source: PVGIS 5.2 (EU Joint Research Centre), optimal tilt and local horizon.
-
Rainwater67/100
~£260/yr
less mains water with a 5,000 L tank (≈82,110 L/yr harvestable from a 100 m² roof)
The detail
Realistic outlook
966 mm of rain a year makes rooftop rainwater harvesting highly productive in Cardiff.
Watch-outs
Harvested rain is non-potable by default — keep it separate from drinking water and add a first-flush diverter.
Grants & tips
Many UK water companies offer subsidised or free water butts; on a metered supply, harvested rainwater cuts your water bill directly.
Average annual rainfall : 966 mm — Source: NASA POWER, MERRA-2 corrected precipitation.
£4,372
Ranked by annual value. The order of the works themselves does not change: insulate before you equip.
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Estimate your solar system in Cardiff
Estimate your solar system in Cardiff
Based on a local yield of 1,032 kWh/kWp per year.
Indicative estimate (production = kWp × local yield). Real output depends on roof orientation, shading and your self-consumption rate.
Climate month by month in Cardiff
In Cardiff, a 3 kWp array pitched at 40° and facing 4° west of south — the optimum PVGIS computes for this location — produces about 3,096 kWh a year. May is the strongest month, at about 387 kWh, and December the weakest, at 105 kWh. November to February bring 17% of the year's output — enough for a battery to cover winter evenings on sunny days, not through grey spells.
The heating season runs from September to June: 10 months average below 15 °C, and February is the coldest at 5.1 °C. In a typical year the coldest hours drop to about -1 °C, the point a heat pump has to be sized for: a standard air-to-water heat pump copes comfortably in an insulated house.
Frost is possible until mid-March and returns from late November, which leaves about 256 frost-free days; tender crops such as tomatoes, beans and squash go outside once mid-March is past. Days above 30 °C are rare, so summer care is mostly steady watering.
Mean wind at 10 m is 4.9 m/s: borderline for a small turbine, which would need an exposed, unobstructed mast to pay off. The southern horizon is open (at most 1.9°) in PVGIS's elevation model, so low winter sun reaches roofs unless nearby buildings block it.
Compared with Bristol, 41 km away, Cardiff has 1% more solar yield, 31 more frost-free days and a heating need 7% lower. Compared with Swansea, 55 km away, Cardiff has 1% less solar yield, 31 fewer frost-free days and a similar heating need.
| Month | Mean temperature | Solar output, 3 kWp |
|---|---|---|
| January | 5.6 °C | 111 kWh |
| February | 5.1 °C | 168 kWh |
| March | 6.5 °C | 270 kWh |
| April | 9.1 °C | 354 kWh |
| May | 11.7 °C | 387 kWh |
| June | 14.7 °C | 378 kWh |
| July | 16.4 °C | 378 kWh |
| August | 15.9 °C | 330 kWh |
| September | 14.6 °C | 288 kWh |
| October | 12.2 °C | 192 kWh |
| November | 8.6 °C | 132 kWh |
| December | 6.2 °C | 105 kWh |
Frequently asked questions — Cardiff
How much could solar panels generate in Cardiff?
A well-oriented 3 kWp rooftop array in Cardiff produces about 3,096 kWh a year, worth roughly £774 in self-consumption. A 6 kWp system reaches about 6,192 kWh/yr where the roof allows. Smart Export Guarantee (SEG): your supplier pays for surplus solar exported to the grid, plus 0% VAT on residential solar PV and battery storage until 2027.
Is rainwater harvesting worth it in Cardiff?
Yes. A 60 m² roof in Cardiff can capture about 49,266 litres a year for the garden, WC and washing machine. Keep harvested rain separate from drinking water and fit a first-flush diverter. Many UK water companies offer subsidised or free water butts; on a metered supply, harvested rainwater cuts your water bill directly.
What grants help with low-carbon heating in Cardiff?
Boiler Upgrade Scheme: £7,500 towards an air-source heat pump (England & Wales); ECO4 and the Great British Insulation Scheme fund insulation, plus 0% VAT on heat pumps. Insulate first — a heat pump only pays off in a well-insulated home (2,720 heating-degree-days here), so prioritise the roof and walls before sizing the unit.
How much food can a garden grow in Cardiff?
With about 256 frost-free days, a 100 m² garden in Cardiff yields roughly 295 kg of fresh fruit and vegetables a year — a partial share of a household's needs, not full calorie autonomy. Council allotments (Allotments Act) give cheap growing plots; RHS and community-garden schemes support home food production.
When is the last frost in Cardiff?
Frost is possible until mid-March and returns from late November, which leaves about 256 frost-free days; tender crops such as tomatoes, beans and squash go outside once mid-March is past.
How much does solar produce in winter in Cardiff?
December is the weakest month: a 3 kWp array makes about 105 kWh, against 387 kWh in May. November to February add up to 17% of the yearly total.
How this score is calculated
Public climate data (PVGIS, European Commission) weighted by how vital each dimension is. The score sharpens once you enter your own home. See the full methodology.
Sources
- Solar energy — Source: PVGIS 5.2 (EU Joint Research Centre), optimal tilt and local horizon.
- Rainwater — Source: NASA POWER, MERRA-2 corrected precipitation.
- Food growing — Source: PVGIS, hourly ERA5 temperatures 2005–2015 (frost dates).
- Low-carbon heating — Source: PVGIS, hourly ERA5 temperatures 2005–2015 (base 18°C).
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