The short answer: In the 8,000 m² example below, a single full retrofit (CHF 245,000) reduces first‑year energy costs from CHF 212,000 to CHF 36,000, giving CHF 176,000 in year‑1 savings and a net year‑1 cost of CHF 69,000 (CHF 8.63/m²). Phasing the same work into four stages (4 × CHF 5,000 mobilization) raises installation outlay by CHF 15,000 and leaves you with CHF 92,000 in year‑1 energy savings, for a net year‑1 cost of CHF 168,000 (CHF 21.00/m²). That makes the phased route CHF 99,000 worse in year‑1 economics and about CHF 12.38/m² more expensive. Below I show the full math, what drives the gap, and how to decide which route is right for you.
In this article:Phasing delays the moment when the whole site benefits from lower energy use. That delay creates two cost effects in year one: repeated on‑site setup costs and forgone energy savings while parts of the site still run on the old system.
Those two effects are the reason a staged approach can look more expensive on paper even if the unit price of fixtures is identical.
We managed an 8,000 m² conversion that was quoted at CHF 245,000 all‑in. The customer chose a phased rollout in four stages over 12 months. The installer charged CHF 5,000 mobilization for each visit.
Because the full site didn’t run on the new system until the final phase, the customer missed substantial first‑year energy savings they would have realised with a single retrofit. That forgone saving is central to the numbers below.
Here are the inputs you supplied and the calculations I used.
Installation cost: CHF 245,000.
Year‑1 energy savings: CHF 212,000 − CHF 36,000 = CHF 176,000.
Net year‑1 cost (installation − savings): CHF 245,000 − CHF 176,000 = CHF 69,000.
Net year‑1 cost per m²: CHF 69,000 ÷ 8,000 = CHF 8.625/m².
Base installation cost (same fixtures & labour): CHF 245,000.
Additional mobilization cost vs single visit: (4 − 1) × CHF 5,000 = CHF 15,000.
Total installation cost (phased): CHF 245,000 + CHF 15,000 = CHF 260,000.
Year‑1 energy savings during phased rollout: CHF 212,000 − CHF 120,000 = CHF 92,000.
Net year‑1 cost (installation − savings): CHF 260,000 − CHF 92,000 = CHF 168,000.
Net year‑1 cost per m²: CHF 168,000 ÷ 8,000 = CHF 21.00/m².
Absolute net cost difference (phased − single): CHF 168,000 − CHF 69,000 = CHF 99,000.
Net cost per m² difference: CHF 21.00 − CHF 8.625 = CHF 12.375/m².
Practical takeaway: in year one the phased route costs the customer CHF 99,000 more and raises the per‑m² net cost by ~CHF 12.38.
What it is: setup, access equipment, crew travel and safety preparations that happen every visit.
What it adds: in this example, three extra visits × CHF 5,000 = CHF 15,000. That is a concrete, line‑item gap you can negotiate or avoid.
What you get: reduced logistical risk and smaller downtime windows — but you pay for it.
What it is: the difference between the energy you'd save if the whole site were converted immediately versus the partial savings while only parts are converted.
What it adds: CHF 176,000 (single‑shot savings) − CHF 92,000 (phased savings) = CHF 84,000 in forgone first‑year savings in this case.
What you get: a smoother cashflow and operational continuity, at the cost of delayed full energy benefits.
What it is: work to integrate lighting controls across phases so the final system functions as one. This can be repeated or require retro‑work if phases use inconsistent hardware.
What it adds: varies by system and supplier. I can’t give a precise CHF figure without your control plan, but inconsistent choices often force rework that increases total cost.
What you get: immediate or staged control benefits depending on the chosen strategy.
Consider phasing if your operation cannot tolerate a long shutdown, if you need to spread CAPEX across budget periods, or if specific zones must be prioritised for safety reasons.
Avoid phasing if year‑1 economics matter most, if the installer’s mobilization fee is high, or if funding requires a single full application. In the 8,000 m² case above, the worse year‑1 cost and forgone savings made phasing financially unattractive.
Insist on a simple one‑page comparison from your supplier that shows: total installation cost, extra mobilization, year‑1 energy cost, and net year‑1 cost for both single and phased options.
Yes — if the installer’s mobilization is very low, if you can keep fixtures and controls consistent across phases to avoid rework, or if funding or operational constraints force staging. You should model the specific numbers to know for sure.
Possibly. A multi‑year cashflow model shows when (or whether) the phased scenario catches up. In many cases the single retrofit keeps the lead, but long‑term maintenance or capex timing can shift the result. I can run that model for you.
Negotiate. Reducing mobilization per visit from CHF 5,000 to CHF 2,500 cuts the extra phased mobilization almost in half and materially improves year‑1 outcomes. Always test several mobilization assumptions.
Resolution: Don’t choose phasing on intuition. Run the numbers: base CHF/m², written mobilization per visit, and the expected energy profile during rollout. That math shows the real year‑1 difference.
Relevant next step: Send your floor plans, operating hours and the supplier’s mobilization fee. We will produce a one‑page comparison (single vs phased), a sensitivity table for mobilization, and a 5‑year cashflow if you want long‑term perspective.
Reintroduce: A conversion in phases has to be properly calculated. That’s where Sensora Smart AG comes in. Book an appointment.
About the author: Dan Flühmann is Head of Projects at Sensora Smart AG. He led the 8,000 m² conversion described here and advises commercial and industrial customers on LED conversions, staged rollouts and controls integration.
Last updated: 2026-06-10