Ask what the winter was doing

The number, and the catch

Dutch greenhouses run at roughly one gigajoule per square metre per year.

That figure comes with a condition attached, and the condition matters as much as the number: it is temperature-corrected.

A mild winter makes any greenhouse look efficient. A hard one makes the same building look wasteful. Strip the correction out and you are no longer measuring the greenhouse — you are measuring the weather that year.

When someone shows you an energy figure, ask which winter it came from.

Keep the heat in before you argue about where it comes from

Screens are the cheapest lever anyone has. They work every night of the season, so the saving compounds in a way a one-off equipment decision never does. In cold climates a second screen is simply standard.

The covering sets the baseline loss underneath that.

Only once the demand is as small as it is going to get does the heat source question become interesting — boiler, geothermal, heat pump. Choosing a source before cutting demand means buying a bigger installation than you needed.

Every euro saved here can cost you a kilo

This is the trap.

A screen pulled shut for insulation is a screen standing between the crop and the sky. Light is yield, near enough one for one.

So a greenhouse optimised purely for low energy is a greenhouse that grows less. You can win the energy argument and lose the business.

The number that actually matters is energy per kilo produced, not energy per square metre.

Lighting cuts both ways

Lamps buy winter production and add a continuous electrical load.

And the technology choice reaches further than people expect. High-pressure sodium throws warmth into the crop; LED does not. Switch to LED and lighting energy falls while heating demand rises. The two systems are one decision.

DutchGreenhouses® models heating, screening, lighting and covering as a single energy balance against the real climate of your site — the extremes, not the averages. Get in touch with a location and we will run it.

From the knowledge base

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