Case Study: Orchard View 4-Bed Passive-Ready Home
Introduction
How upgrading from 4.5kWp to 6.5kWp solar + battery storage saved £4,200 in VAT and secured first-time BREL compliance.
Project Overview
Location: Wiltshire
Build Type: Timber frame, 4-bedroom detached
Target Standard: Passive House-ready (not certified)
Completion: November 2025
The Challenge
The client approached us after their initial SAP assessment failed to meet Part L targets. Their architect had specified a 4.5kWp solar array (1.125kWp per bedroom)—below the industry compliance benchmark.
Further analysis revealed:
- TPER exceeded TER by 8%
- No battery storage specified (reducing self-consumption)
- Suboptimal panel layout due to roof constraints
Our Intervention
We redesigned the renewable energy system with three key changes:
1. Upgraded Solar Capacity
Increased from 4.5kWp to 6.5kWp by:
- Using higher-efficiency 400W panels (vs. 300W originally specified)
- Optimizing panel layout across both roof slopes
- Adding 1kWp to south-facing garage roof
2. Added Battery Storage
Specified a 10kWh battery system to:
- Increase self-consumption from 40% to 75%
- Reduce grid dependence during winter months
- Improve TPER calculation by reducing imported energy
3. Ensured 0% VAT Eligibility
Restructured the contract to ensure:
- MCS-certified installer handled both supply and installation
- Single invoice showing 0% VAT rate
- Installation completed before 31 March 2027 deadline
Financial Impact
| Item | Cost (ex VAT) | VAT Saved |
|---|---|---|
| Additional 2kWp solar | £2,400 | £480 |
| 10kWh battery system | £6,500 | £1,300 |
| Enhanced inverter | £1,800 | £360 |
| IntegraVolt redesign fee | £1,200 | £240 |
| Total | £11,900 | £2,380 |
Additional savings: Avoided £1,800 in re-work costs by getting SAP approval before construction began.
Total project savings: £4,200
The Result
- ✓ SAP 10.2 Pass: TPER now 6% below TER (comfortable margin)
- ✓ BREL Compliance: First-time approval with full photographic evidence
- ✓ 0% VAT Applied: £2,380 saved on renewable installations
- ✓ Future-Proof: System sized for EV charging and potential heat pump upgrade
"IntegraVolt saved our project. We were facing a potential 6-month delay and significant re-work costs. Their redesign not only got us compliant but actually improved the home's long-term performance and running costs."
— Client, Orchard View Project
Written by the Integravolt Technical Team
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Consultant's Corner
Pro Tip: When documenting your project for VAT purposes, photograph every thermal junction before plasterboard goes up. This evidence becomes critical if HMRC audits your claim.
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