Are solar panels worth it in St Helens?

A first year, three roofs

Output: PVGIS 5.3 for central St Helens, 14% losses. The chimney row takes off the direct-sun share our shade checker gives for that stack, applied to the whole output, which slightly overstates the loss. Unit value: 26.32p per kWh, Ofgem's cap average for October to December 2026. Export rates are illustrations. Read 3 November 2026.

What moves the answer most

• Use at home. Each unit you use instead of buying is worth the full unit rate; each unit exported earns the export rate, a fraction of it. Running appliances in daylight is the cheapest way to raise the value.
• The export tariff. Large suppliers must offer some rate for exports from an MCS-certified system, but rates vary widely. Check what yours pays before comparing quotes.
• Heavy shade. Light winter shade barely shows. Shade through the middle of spring and summer days costs far more, because that is when most of the year's output is made. Measure it with the shade checker.
• The price. Small terrace systems cost more per kW; see prices.

The household matters as much as the roof

Take the clear south-facing roof and change nothing but the share of its output used in the house:

Moving from a fifth to two-thirds used at home is worth more than the difference between a clear roof and one with a chimney stack in front of it. Someone at home in the day, washing run at lunchtime, a hot-water diverter or a battery each moves a household down this table; the last of these has a price, set out on batteries.

When the output arrives

In PVGIS's monthly figures for central St Helens, a south roof at 35 degrees makes 70% of its year between April and September and only 10% in November, December and January together. Two things follow. Shade that falls in the summer half of the year costs far more than winter shade, however dramatic December's shadows look. And most of the output arrives when days are long, so it is the summer pattern of use at home that decides how much is used rather than exported.

The east or west roof, looked at again

The east-or-west roof in the first table makes about 79% of the clear south roof's output, so on kWh alone it trails. But it makes its electricity earlier or later in the day, when more households are cooking, washing or heating water, and less of it piles up at midday to be exported for a few pence. If that lets you use a bigger share of it, the gap in value is smaller than the gap in output. On a terrace whose slopes face east and west, panels on both can give a long, flat day of output rather than a midday peak.

If the cost is covered another way

A household that qualifies for the Warm Homes: Local Grant may have panels fitted under the scheme, in which case value matters less than eligibility; grants and loans sets out the tests. A loan adds interest, which belongs in your own version of these sums. And a quote well above the North West averages on prices drags every figure here down, so test it with checking an installer before deciding.

A year on

After twelve months, compare three things: the year's output from the inverter's app against PVGIS for your roof, less any shade factor the quote used; how much less you bought from your supplier; and what the export tariff paid. Those three numbers replace the assumptions on this page with your own.

When to think twice

• The only usable roof faces north, or is shaded through the middle of the day for much of the year.
• The roof needs re-covering soon. The Warm Homes Loan will not pay for roof work, and lifting panels later means a second scaffold.
• You rent, unless the landlord agrees in writing.

Why no payback date

A payback date needs electricity prices and export rates for ten or twenty years ahead, and your own use over that time. Nobody knows those. A first-year figure with its assumptions stated is something you can check, and redo each year with real prices.

Related pages

• Shade checker
• Prices
• Batteries
• Grants and loans

References

1. Ofgem: how export payments work for small generators
2. PVGIS 5.3 photovoltaic estimates (EU Joint Research Centre)
3. Ofgem: the energy price cap, unit rates by region
4. NOAA Global Monitoring Laboratory: general solar position calculations
5. HMRC Notice 708/6: zero rate for installing solar and batteries in homes
6. Ofgem (May 2026): typical domestic consumption values
7. Department for Energy Security and Net Zero: solar PV cost data (2025/26)