iDistributedPV Newsletter – Homeowner case study

The iDistributedPV partners ran the first simulations for the homeowner case study in 5 different countries (Spain, Germany, Lithuania, Poland, Greece) based on different power flow analysis tools and the Prosumer Solution Simulation Tool (public version) :, which was developed for the project.

For Spain’s homeowner case study, a typical four-inhabitant household was chosen for the simulations. Different PV power systems were studied: PV capacity ranging from 1 to 5 kW, with and without storage devices. It was supposed that the surplus electricity generated could be sold back to the grid according to the wholesale price of the market. The results clearly show that the main benefit obtained from PV systems comes from self-consumption. Beyond certain size – 3 kW – the profitability of this solution decreases because the rate at which self-consumption increases is far less than the increase in the cost of the installation. Although there is more surplus energy sold back to the grid, the actual benefits come from savings in the bill. Batteries efficiency and price are not yet suitable to make a positive impact on the profitability of the installations; in cost terms, they should become around 70% cheaper. Regarding the grid integration of prosumers in the electricity system, a low voltage grid comprising 55 households was analysed. When there are up to 50% of prosumers in the grid with a PV power capacity of 2 kW, there are neither over-voltages nor under-voltages present in the grid. It has been observed that prosumers located at the beginning of the grid, close to the infeed, cause less overvoltage violations when the level of penetration is above 50%. The thermal loading of the components of the grid is below 100% in all cases. When batteries are used along with the PV power systems, the maximum loading of the grid decreases up to a certain point, and then it starts to grow.

The simulation results and recommendations for a residential prosumer in Germany are based on the electricity market and regulatory framework, which is mainly characterised by a PV feed-in tariff fixed for 20 years. The existing profitability (positive NPV) raises with increasing installed PV capacity, until 10 kW is reached. Therefore, the prosumer should make use of the maximum suitable roof surface area. Similarly, the profitability of a PV system of a household with a high electricity demand performs better compared with one having a lower electricity demand. Adding a battery reduces the profitability of the PV system despite the gained self-sufficiency. To reach economical parity with PV systems without a battery, battery prices must drop to 400 – 500 €/kWh. Regarding the effects on the German grid it can be observed that distribution grids with a high decentralized PV feed-in benefit from stationary batteries and especially positive voltage deviations substantially decline.

In Poland, the homeowner case study is tested in the region of Poznan. Different PV generation and household loads scenarios are tested, with the maximum allowable PV installation set at 14.5kW. The simulations show no limitations for prosumers with typical 4 kW installations or maximum PV installation. No load (0kW) or maximum contracted load (12.5 kW) subcases makes no impact. Furthermore, a household with different PV installations (1-8 kWp) and two different load scenarios (3kWh and 6kWh per year) is tested. PV electricity is consumed according to current demand and its surplus will be exported to the public grid. Due to specific Polish regulations, it is possible to get back 80% of the exported energy. The simulations show that maximum profitability occurs at 3kW installation in both cases.

The simulations in Lithuania are based on the electricity market and regulatory framework, which are characterised by the use of net-metering with four payment options for energy storage in the grid services. The received modelling results show that in most of the cases, payback time is more than 10 years for the homeowners and could slightly decrease with the increase of PV capacity up to 10 kWp. Regarding the effects on the Lithuanian grid, it can be concluded that existing household PV installations and those that are planned to be installed up to year 2020 will not have any negative impact towards distribution grid parameters.

In Greece, net-metering (annual energy offset between the generated and the consumed energy) is the only viable scheme for homeowners with PV installations. For the simulation, 3 different households – 2 full-year and 1 vacation residence – are tested with different PV installation scenarios (1-6kWp). The results show that for lower PV installation the IRR is higher, but when the amount of energy fed into the grid approaches the energy bought from the grid (but not become equal or higher), the NPV tends to reach its maximum. Moreover, the degree of self-sufficiency does not present significant differences if the PV installation surpasses a certain value (almost the point where the NPV reaches its maximum).