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)	1,150-1,200 kWh/kWp	1,750+
Hertfordshire	1,050-1,100 kWh/kWp	1,580

A 5kW system in Portsmouth generates approximately 5,750-6,000 kWh per year. The same system in St Albans generates 5,250-5,500 kWh. Over a 25-year system life, that's around 12,500 kWh of additional generation in Hampshire.

For a deeper Hampshire-specific perspective, Solent Solar's analysis of the Hampshire market covers the south coast's regional dynamics in detail.

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.