South East Solar: Why Hampshire Outperforms Hertfordshire on Yield
Hampshire and Hertfordshire have different solar yield profiles. Here's why, and what it means for system sizing in each region.
South East Solar: Why Hampshire Outperforms Hertfordshire on Yield
The South East of England is generally treated as one solar market, but there are meaningful regional differences within it. Hampshire — particularly the south coast — outperforms Hertfordshire on annual solar yield by roughly 5-8%.
The Numbers
| Region | Annual Yield | Average Sun Hours |
| Hampshire (south coast) | 1,000-1,100 kWh/kWp | 1,750+ |
| Hertfordshire | 950-1,050 kWh/kWp | 1,580 |
A 5kW system in Portsmouth generates roughly 5,000-5,500 kWh per year. The same system in St Albans generates roughly 4,750-5,250 kWh. Over a 25-year system life that difference adds up to somewhere around 6,000 kWh of extra generation on the south coast — real, but far smaller than the gap in the electricity tariff you are offsetting.
Implications for Hertfordshire System Sizing
Because Hertfordshire generates slightly less per kWp, system sizing should err on the higher end of usage projections. We typically recommend:
- Average household (2,500-3,500 kWh/year): 4-5kW system
- Higher usage (3,500-4,500 kWh/year): 5-6kW system
- EV + heat pump household: 6-8kW system minimum
Hampshire customers can often size 10-15% smaller for the same energy outcome.
What Doesn't Vary Between the Regions
Equipment costs, installer quality requirements, and battery economics are largely consistent across the South East. The differences are:
- Yield — geographic, not changeable
- Local planning rules — vary by district council
- Conservation area density — Hampshire has more rural conservation, Hertfordshire more urban
For Hertfordshire homeowners, the practical takeaway is that your system needs to be sized correctly for the regional yield rather than relying on national average figures. Get in touch for a Hertfordshire-specific yield calculation.
