Biodiversity net gain cost: assessment fees and delivery cost

The two halves

Assessment fee

The ecology consultant's fee: a habitat survey, the statutory biodiversity metric calculation, the biodiversity gain plan, and any habitat management and monitoring plan. Professional time, scoped on site size and habitat complexity.

Delivery cost

What it costs to actually produce the 10 percent gain: on-site habitat creation and its 30 years of management, off-site units bought from a habitat bank or landowner, or statutory biodiversity credits at gov.uk published prices as a last resort.

The delivery cost usually dominates, and it is set long before anyone quotes: it is decided by the habitats your site currently supports and by how much of the site the layout consumes. The single most effective cost control on BNG is getting a baseline calculation early enough to influence the masterplan.

What drives the assessment fee

• Site size and habitat complexity. A hectare of arable is quick; a mosaic of scrub, hedgerow, watercourse and unimproved grassland is not, because every parcel has to be classified and condition-assessed.
• Whether a UKHab survey is required. A full habitat survey classified to the UK Habitat Classification is a site visit plus mapping plus write-up. Some small sites can use the simpler small sites metric instead.
• Survey season. Botanical condition assessment is only reliable within the growing season. Instructing outside it means either waiting or accepting caveats, and waiting has a programme cost that dwarfs the fee.
• Linear habitats. Hedgerows and watercourses are measured and traded separately from area habitats, and each adds work.
• On-site against off-site delivery. An on-site scheme needs a design, a management plan and monitoring commitments. An off-site solution needs unit sourcing and legal agreement input instead.
• Monitoring obligations. gov.uk states habitats must be maintained for a minimum of 30 years, with responsibilities set out in a legal agreement. Costing that long tail properly is part of the work.
• Protected species overlap. BNG is not an ecological impact assessment. If bats, great crested newts, badgers or nesting birds are in play, those surveys are separate instructions with their own seasons.

What drives the delivery cost

• The baseline you start with. Higher distinctiveness habitat on site means more units to replace, and trading rules restrict what can substitute for what.
• How much space the layout leaves. Retained and enhanced habitat within the red line is almost always the cheapest unit you will ever get.
• Whether off-site units are available locally. Spatial considerations affect what off-site units are worth to your scheme.
• The statutory credit ceiling. Statutory credits are published at fixed prices, and gov.uk states that 2 credits must be bought for every 1 unit. That published price is the reference point against which any private offer should be judged. See the credit price table.

How to get comparable quotes

1. Send every consultant the same pack: red line boundary, site area, an aerial image, the proposed layout if you have one, and the target submission date.
2. Ask for the scope in stages: baseline survey and metric, then gain plan, then management and monitoring plan. Staged fees let you stop if the baseline changes the scheme.
3. Ask when they can actually survey. A cheaper fee that misses the season is not cheaper.
4. Ask whether protected species surveys are included or quoted separately, and what triggers them.
5. Ask what happens if the LPA queries the metric. Responding to validation and consultee comments should be in the fee or clearly priced.

We do not publish ecology fee ranges or private off-site unit prices, because neither is officially published and both move with habitat, location and season. The published statutory credit prices are in the table on the home page.