Solar Panels for Swimming Pools

How it works: 1. Solar PV panels generate electricity 2. The electricity powers a pool heat pump 3. The heat pump extracts heat from outdoor air (even cold air contains thermal energy) 4. The heat pump transfers 3–4kWh of heat into the pool water for every 1kWh of electricity consumed

Why this is the best option: - Heat pump COP of 3–4 means solar electricity is multiplied 3–4x as heat - Works in UK temperatures down to 5°C (some models work to –15°C) - Extends the swimming season from May–September to April–October - The PV panels also power your home when the pool heat pump is not running - Year-round value from the panels (not just pool heating)

Costs: - 4–6kW solar PV system: £5,500–£11,000 - Pool heat pump (10–20kW thermal): £2,500–£5,000 - Total: £8,000–£16,000 - Annual pool heating savings: £500–£1,500 (vs gas or direct electric heating)

Payback: 6–10 years (including home electricity savings from the solar panels)

Source: Pool heat pump COP data; solar system sizing for pool applications.

How it works: Dedicated solar thermal collectors (usually unglazed, flexible plastic mats) are installed on the roof. Pool water is pumped through the collectors, heated by the sun, and returned to the pool.

Types: - Unglazed collectors (most common for pools): black plastic or rubber mats - Glazed flat plate collectors: more expensive but work in cooler weather - Evacuated tube collectors: most expensive, best for year-round

Costs: - Unglazed solar pool heating system: £2,000–£5,000 - Roof area needed: typically equal to 50–100% of pool surface area

Pros: - Directly heats water — no electricity conversion - Simple system (pump + collectors + controller) - Low maintenance

Cons: - Only heats the pool — cannot power home appliances - No SEG income (no electricity exported) - Less effective in cloudy/cool weather than PV + heat pump - Seasonal — provides little value in winter

Verdict: Solar thermal is simpler and cheaper for POOL-ONLY heating. But solar PV + heat pump is more versatile (powers everything + heats pool) and delivers better year-round value.

Source: Pool solar thermal system specifications; installer pricing.

Annual pool heating costs comparison (10m × 5m outdoor pool, May–September):

| Heating Method | Annual Cost | Pros | Cons | |---------------|-------------|------|------| | Gas boiler | £1,500–£2,500 | Fast heating | Expensive, carbon emissions | | Direct electric | £2,000–£3,500 | Simple | Very expensive | | Air source heat pump (grid) | £500–£900 | Efficient (COP 3–4) | Still uses grid electricity | | Heat pump + solar PV | £100–£300 | Near-free with solar | Higher upfront cost | | Solar thermal only | £50–£200 | Directly heats water | Seasonal, no electricity |

Solar PV + heat pump reduces pool heating costs by 80–95% compared to gas or direct electric. The upfront investment (£8,000–£16,000) is recovered within 6–10 years through combined home + pool savings.

Source: Pool heating cost data; Energy Saving Trust.

How much extra solar do you need for a pool heat pump?

A typical outdoor pool (10m × 5m) requires approximately 10–15kW of thermal input per day during the swimming season.

With a heat pump (COP 3.5): 10kW thermal ÷ 3.5 = ~3kW of electricity per day for pool heating.

A 3kW solar addition (8 panels) generates approximately 10–15kWh/day in summer — enough to cover pool heat pump electricity during the swimming season.

Recommended system for home + pool: - Home: 4kW (10 panels) - Pool: 3kW (8 panels) - Total: 7kW (18 panels) - Cost: £9,000–£13,000 (panels + installation) - Plus heat pump: £2,500–£5,000

In summer: Panels generate 25–30 kWh/day, covering home (8kWh) + pool heat pump (3kWh) with surplus to export or charge a battery.

Source: Pool heating calculations; PVGIS summer generation.