Fig. 35: Energy use efficiency (= marketable yield per used energy) for tomatoes under different light sources

4.4.3 Light related costs

Since the application of the electricity law 65/2003 in 2005, the cost for electricity has been split between the monopolist access to utilities, transmission and distribution and the competitive part, the electricity itself. Most growers (95%) are, due to their location, mandatory customers of RARIK, the distribution system operator (DSO) for most of Iceland except in the Southwest and Westfjords.

The government subsidises the distribution cost of growers that comply to certain criteria’s. In recent years, the subsidies fluctuated quite much. In the year 2019 was about 95% of variable cost of distribution subsidised according to Orkustofnun (National Energy Authority of Iceland), which resulted in costs of about 1 ISK/kWh for distribution, while for the sale values amounted 5,77-6,53 ISK/kWh. However, it has to be taken into account that big vegetable growers can get at least 50% discount on the tariff values. Based on this information, were energy costs for seedling production of tomatoes and their continuous production calculated (Tab. 8). Costs for electricity were naturally higher for seedlings grown under HPS lights due to the higher use of electricity. Investment costs into lights were nearly three times higher for LEDs compared to HPS lights for young plant production. However, as young plant production did only take a small part into the whole production and investment costs into “Hybrid” and “Hybrid+LED” did not differ much in continuous production, were total investment costs into lights only by 9% increased when plants received LEDs in young plant production compared to HPS lights in young plant production. The selection of “Hybrid+LED” or “Hybrid” did not influence the total investment costs into lights.

In total were light related costs (electricity costs + investment into lights) of seedling production and continuous production about 3% higher for light treatments that received young production under LEDs (“LED, Hybrid+LED,” “LED, Hybrid”), while Hybrid “(HPS, Hybrid”, “LED, Hybrid”) was about 12% more expensive than Hybrid+LED (“HPS, Hybrid+LED”, “LED, Hybrid+LED”) (Fig. 36).