Growers with combined heat and power (CHP, or WKK in Dutch) should evaluate LED lighting by modeling the whole greenhouse energy system, not the lamps alone. The business case combines electricity savings, the heat the CHP no longer needs to replace, lost power sales, and crop effects, compared against the investment.
The result depends mainly on how much heat HPS lamps currently supply, what your boiler or CHP must make up, and the electricity market. The sections below cover the questions growers ask most often when running this calculation.
How does switching from HPS to LED change CHP heat output?
Switching to LED reduces the radiant heat released inside the greenhouse, so the CHP and boiler must supply more heat from the heating system. HPS lamps convert a large share of their input power into heat, while LED fixtures convert more of it into usable light and release less heat into the crop space.
In practice, that heat did not disappear from the greenhouse energy balance; it moved from the lamps to the heating system. In winter, the heat your HPS lamps provided now has to come from the CHP, the boiler, or a heat buffer. The effect is strongest in cold, dark months, which matters for growers in Canada, the northern United States, and Scandinavia, where lighting hours and heating demand overlap heavily.
Two additional points affect the heat balance:
- Light distribution and crop climate: LED fixtures can be placed closer to the crop, and many designs allow more control over radiant heat at leaf level, which changes how you manage humidity and temperature.
- Heat demand timing: Because lighting hours often coincide with CHP run hours, any reduction in lamp heat shifts when and how much heat the CHP must deliver.
What costs and savings belong in the LED business case?
A complete LED business case includes the investment, installation, electricity savings, extra heating cost, lost CHP revenue or changed dispatch, maintenance, and crop performance effects. Leaving out any of these produces a misleading payback figure, especially in a CHP greenhouse where electricity and heat are linked.
Costs to include
- Fixtures, installation, electrical upgrades, and any grid connection changes
- Additional heating energy to replace the heat previously supplied by HPS lamps
- Changes to climate control, screens, and heating system settings
- Lost income if the CHP runs fewer hours or sells less electricity
Savings and benefits to include
- Lower electricity consumption per unit of light delivered
- Reduced lamp replacement and maintenance costs
- Yield, quality, or uniformity improvements from crop-specific light recipes
- Better control of dimming and light timing, which allows use of cheaper electricity hours
Crop benefits deserve a cautious, evidence-based treatment. Use trial results or comparable projects for your specific crop, whether tomato, cucumber, or lettuce, rather than generic uplift assumptions.
How do electricity prices and spark spread affect the outcome?
Electricity prices and spark spread determine how valuable it is to keep the CHP running. Spark spread is the margin between the electricity price and the gas cost needed to produce it. A wide spread favors running the CHP and exporting power; a narrow one favors buying electricity from the grid.
For the LED case, this matters in two ways. First, a high electricity price makes the efficiency gain of LED more valuable because each saved kilowatt-hour is worth more. Second, a strong spark spread can make CHP production profitable even with reduced lighting load, changing how you value the extra heat the system must supply.
Because both power and gas prices move, test several scenarios rather than one forecast. A sound approach is to model a low, base, and high price case and check whether the investment still performs in the low case. Local conditions also differ: grid tariffs, export rules, and incentives vary between the Netherlands, Canadian provinces, US states, and Scandinavian countries, so use regional tariff structures in the model.
Should growers keep running the CHP after installing LED?
Most growers should keep the CHP only when it still earns a positive margin on electricity sales and delivers heat they can actually use. After LED installation, the answer depends on spark spread, heat demand, CO2 needs, and whether the CHP can operate flexibly.
Evaluate the CHP on the following criteria:
- Heat utilization: Can you use or buffer the heat the CHP produces during the hours it runs?
- Electricity margin: Does exporting or self-consuming CHP power beat buying from the grid?
- CO2 supply: If the CHP supplies CO2 for the crop, what is the cost of the alternative source?
- Flexibility: Can a heat buffer let the CHP run only when prices are favorable?
A CHP that was sized for HPS lighting load may be oversized for an LED greenhouse. In that case, some growers run it fewer hours, add heat storage, or reduce reliance on it over time. The key is to compare the CHP as a standalone profit center against the alternative of boiler heat plus grid electricity.
How do you calculate payback and return on LED investment?
Calculate payback by dividing the net investment by the annual net benefit, where the net benefit is electricity savings plus crop gains minus extra heating cost and lost CHP margin. For a fuller picture, also calculate net present value and internal rate of return over the fixture lifetime.
Follow these steps:
- Establish a baseline: annual electricity use, gas use, CHP hours, power revenue, and heat balance under HPS.
- Model the LED scenario with the same crop schedule and light levels, including the heat shift.
- Calculate the annual difference in energy cost and CHP revenue.
- Add maintenance savings and realistic crop benefits, using conservative assumptions.
- Subtract the net investment after any subsidies or tax benefits.
- Run price scenarios and compute payback, NPV, and IRR.
Be cautious with the payback period alone. A short payback in a high price scenario can disappear when spark spread narrows. Present the range, not a single number, when discussing the decision with financiers or partners.
Which LED strategy suits CHP-equipped greenhouses best?
The best strategy for most CHP greenhouses is a staged or hybrid approach: install LED where it delivers the most crop and energy benefit, keep or adapt the CHP based on spark spread, and add heat storage for flexibility. Full LED conversion makes the most sense when electricity savings clearly outweigh the added heating cost.
Common strategies include:
- Full LED replacement: Maximum electricity savings and light control, with the largest change in heat demand.
- Hybrid LED and HPS: Keeps some lamp heat and CHP synergy while capturing part of the efficiency gain.
- Interlighting with top LED: Adds light inside the crop canopy, relevant for tall crops like tomato and cucumber.
- Phased conversion: Spreads investment over seasons and lets you validate results before scaling.
The right choice depends on crop, region, existing CHP size, and energy contracts. A lettuce grower with high light needs in Scandinavia faces a different balance than a tomato grower in southern Canada, so tailor the strategy to the cultivation plan rather than copying a standard layout.
How Dutch Lighting Innovations Helps with LED Economics in CHP Greenhouses
Dutch Lighting Innovations (DLI) helps CHP growers build an LED business case that accounts for the full energy system, not just the lamps. As an independent Dutch specialist, DLI designs crop-specific lighting around your cultivation strategy and supports you throughout the growing season.
Specifically, DLI can help you with:
- Crop-specific lighting configurations through its LED lighting products, matched to tomato, cucumber, or lettuce requirements
- Modeling the shift in heat demand and its impact on your CHP and boiler use
- Comparing full, hybrid, and phased LED strategies against your energy contracts
- Ongoing performance optimization after installation
You can see how this works in practice in the Red Harvest project. Ready to test the economics for your own greenhouse? Contact the DLI team to discuss your CHP setup and get a tailored lighting proposal.
