How Much Does a BNG Assessment Cost in 2026?

The most common question developers ask about Biodiversity Net Gain: "How much is this going to cost me?"

The answer ranges from £0 to over £100,000 — depending on your site, your approach, and how early you plan. Here's a realistic breakdown for 2026.

The Full Cost Spectrum

Approach	Cost	When to Use
Automated screening (BioGain Free)	£0	Early feasibility, quick due diligence
Pro subscription (BioGain)	£39/mo	Small site assessment, planning evidence
SSM self-assessment	£39/mo (14-day free trial)	Small sites ≤1 ha, no priority habitats
Preliminary Ecological Appraisal	£500–£1,500	Initial assessment of ecological constraints
Full ecological survey	£2,000–£5,000	Standard sites needing professional assessment
Complex site survey	£5,000–£10,000+	Sites with protected species, multiple habitats
Habitat creation on-site	Varies widely	Part of landscaping scheme
Off-site biodiversity units	£20,000–£50,000/unit	When on-site gain isn't achievable
Statutory credits (last resort)	£42,000+/unit	When no off-site units available

Breaking Down the Costs

1. Screening & Desk Study (14-day free trial, then £39/mo)

This is where you start. Understand what's on your site before committing to expensive surveys. Automated tools like BioGain query government databases to identify habitats, designations, species records, and flood risk — giving you a baseline assessment in minutes.

If the screening shows no priority habitats and the site is under 1 hectare, you might be able to handle BNG entirely with the Small Sites Metric — potentially saving thousands.

2. Ecological Survey (£500–£10,000+)

For complex sites, you'll need a professional ecologist. Costs depend on:

• Site size — larger sites take longer to survey
• Habitat complexity — multiple habitat types need individual assessment
• Protected species — bat surveys alone can cost £1,000–£3,000
• Season — some surveys can only happen at specific times of year
• Location — travel costs, regional rate variation

3. Achieving the 10% Gain

Once you know your baseline, you need to deliver 10% more biodiversity units. Three options:

Option A: On-site habitat creation — The cheapest if done well. Native planting, green roofs, SuDS, wildflower meadows, hedgerow planting. Often achievable within normal landscaping budgets.

Option B: Off-site biodiversity units — Buy units from habitat banks. Prices vary enormously by region and habitat type:

• Area habitat units: £20,000–£50,000+ per unit
• Hedgerow units: £15,000–£30,000 per unit
• Prices are higher in London and the South East

Option C: Statutory credits (last resort) — If you can't find off-site units, the government sells credits at £42,000+ per unit. These are deliberately priced high to encourage on-site and off-site solutions first.

A typical small residential development (5 houses on 0.5 ha) might need 0.1–0.5 additional biodiversity units to hit the 10% target. That's achievable with good landscaping design — no credits needed.

Real-World Example

Let's say you're building 6 houses on a 0.4 ha site of modified grassland:

Cost Item	Amount
BioGain screening (free tier)	£0
BioGain Pro subscription	£39/mo
Native planting scheme (within landscaping budget)	Included
Total BNG cost	£39/mo

Compare that to the traditional route:

Cost Item	Amount
Preliminary Ecological Appraisal	£800
BNG metric calculation	£1,200
Biodiversity Gain Plan	£1,500
Total BNG cost	£3,500

On a simple small site, the difference is £3,451.

How to Minimise BNG Costs

1. Screen early — Know your constraints before you buy the land or finalise designs
2. Design for BNG — Green roofs, native planting, and SuDS deliver biodiversity units as part of normal landscaping
3. Retain existing habitats — Keeping a hedgerow is free. Replacing it costs units.
4. Use the SSM where eligible — Saves £2,000–£5,000 in ecologist fees on small sites
5. Buy local units early — Off-site unit prices are rising as demand increases. Early movers get better deals.
6. Never use statutory credits if you can avoid it — They're the most expensive option by design