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☀️ Solar & Battery Calculator

UK-specific · 2026 real costs · 94% of new installs include a battery

🔧 This calculator uses real 2026 UK solar pricing data (MCS certified), regional generation estimates, and SEG export rates. Prices reflect a typical UK semi-detached house — solar-only from £5k–£9k, solar+battery from £8k–£18k. 0% VAT included. Your mileage will vary by roof orientation, shading, and usage patterns.

📐 Your Setup

📊 2026 UK Solar Market Snapshot

Typical Solar-only Cost
£5,000–£9,000
Panels + inverter + mounting + MCS certification
Solar + Battery Total
£8,000–£18,000
Typical for 4kWp + 5-10kWh battery
Battery Adoption Rate
94%
Of new UK solar installs include a battery in 2026
Electricity Rate
~28p/kWh
Off-peak as low as 7-9p/kWh
SEG Export
4–15p/kWh
Smart Export Guarantee rates
VAT on Installations
0%
Solar + battery — zero VAT rate

Payback period typically 7-10 years (as low as 6 years with good SEG rates). All MCS-certified installations qualify for 0% VAT in 2026.

🏠 Real Setup: Our Powerwall System

Our Hardware

  • 🔋 2 × Powerwall 3 — 27 kWh total capacity (11.5 kW continuous each)
  • ☀️ Solar panels — roof-mounted with microinverters
  • 🚗 Audi Q4 E-Tron — 82 kWh battery, 11 kW AC charging
  • ⚡ Octopus Agile tariff — half-hourly wholesale pricing
  • 📡 Tesla Owner API — cloud monitoring via Home Assistant
💡 Strategy: Charge Powerwall on cheap Agile slots (00:00–07:00), discharge during peak (16:00–21:00). Charge EV during cheapest overnight window. Export solar surplus. System is fully automated via Home Assistant + Tesla API.

What We Learned

  • ✅ Battery-first is key — 94% of new UK installs include battery (2026)
  • ✅ Agile + battery = arbitrage: buy at ~5–10p, avoid 25–100p peak
  • ✅ Powerwall 3 is UK grid-compliant (G99), works with single-phase
  • ✅ Solar + EV is the magic combo — free miles on sunny days
  • ✅ Install took 1 day — Powerwall 3 is AC-coupled, no DC rewiring
  • ⚠️ G99 application needed for dual Powerwall — ~2-4 weeks approval
Battery Capacity
27 kWh
Solar + Battery Cost
~£18k
0% VAT
Powerwall Output
11.5 kW
per unit (23 kW total)
Annual Savings (est.)
~£1,200
Agile arbitrage + solar

📊 Live stats: See energy monitor for real-time Powerwall data — solar generation, battery state, grid flow, and EV charging.

Assumptions: South-facing roof, 30° pitch, no shading. Solar generation estimates from MCS/Energy Saving Trust. System costs include installation, scaffolding, G99/G98 application, and 0% VAT. Prices are 2026 estimates based on verified market research and will vary by installer, roof complexity, and region.

This calculator is for illustration only. Always get at least 3 MCS-certified installer quotes before committing. 94% of new UK solar installations include a battery in 2026 — consider whether battery storage makes sense for your usage pattern.