- Take the simplest approach first, then iterate.
- Use existing cost estimates, starting with those used by Markal.
- Display cost ranges to reflect uncertainty, rather than single cost estimates.
- Cost everything, but use wide ranges where existing information is poor.
- Focus on physical costs (kit, people) over opportunity costs (carbon, social welfare loss) or regulatory costs.
- Focus on costs, not prices (we don't worry about who pays and who profits).
- Present cash flows (e.g., don't amortise capital costs, or worry about starting 'stock')