Solar energy: the smart route to lower electricity bills for housing co-operatives

You can check the conditions on your roof by searching for your address at solkart.no. For commercial buildings, housing co-operatives and jointly-owned properties, farms and solar parks, you can also contact our advisers at bedrift@solcellespesialisten.no. We are always happy to come out for a site survey.

South-facing roof surfaces usually give the highest annual output, peaking around the middle of the day. East- and west-facing surfaces generate more in the morning and the afternoon, which spreads production more evenly across the day. In our own PV calculator on solkart.no, a roof in Oslo gives around 1 006 kWh per kWp a year when the surface is pitched 25 degrees to the south, against around 800 kWh per kWp on a flat roof with panels at 10 degrees to the east and west (run on 17 September 2026, P50, 5% system loss, snow and soiling losses included). Shading from neighbouring rows and the surroundings is not included in the figures. Total annual output is somewhat lower, but east/west can suit you particularly well if your consumption is heaviest early or late in the day. This holds for any type of building, whether a housing co-operative, a barn or an industrial building with a flat roof. You get the figure for your own roof in Solsjekk.

In principle you can have panels on several roof surfaces. Technical requirements do place certain limits on the number of panels per surface. The more surfaces you cover, the more expensive it can become, as more inverters may be needed.

It has to be assessed building by building. A solar energy installation is a building services installation under the Planning and Building Act, pbl. § 20-1 bokstav f. Installing or altering one within a single dwelling unit or fire compartment counts as a simple installation and is exempt from the permit requirement, but a shared installation on a co-operative or jointly owned building usually spans several dwelling units and fire compartments, and then the exemption does not apply. The same goes if the building sits in a conservation area or close to the shoreline or a railway line. The new exemption for solar energy installations that applies from 1 July 2026 covers small houses and certain detached buildings – not blocks of flats and commercial buildings. We help you check this with the council before installation.

Every solar system must be registered with the grid company. We take care of that process; all we need from you is your meter number. The role your building takes on the grid depends on how much the installation can export to the grid. As long as the installation exports no more than 100 kW, you are registered as a plus customer, the formal term for a prosumer – a customer who both uses and produces electricity – and you are paid for the surplus exported to the grid. If it exports more, you become a producer, with separate terms for feed-in and settlement. We establish which category your building falls into before the system is designed.

Once the quote is confirmed, the project manager agrees the installation date with you. When it can happen depends on the scope of the project, delivery of materials and any applications to the local authority and the grid company.

If the goods are marked “damage registered”, that is a routine note from the supplier and something we will follow up. In most cases only the packaging is damaged and the goods themselves are unaffected. If you can see that the goods are extensively damaged, please contact us as soon as possible on 45 72 87 80.

Solcellespesialisten has its own installers, who are experienced in solar installation and have a solid background in both electrical and structural work. We have the capacity to install around two in three projects with our own employees. The rest are carried out by regular subcontractors we have worked with for many years.

As a rule we have our own installers for connecting the solar system to the grid, and they usually come once the roof work is finished. You will receive a separate email with the connection date.

Solar panels are essentially self-cleaning. The installation should still be inspected in line with the manufacturer’s recommendations. The largest installations should have an on-site inspection several times a year, the smallest every three years. An inspection can include a visual check from the ground, plus a look at whether cables are secured and protected. If the panels are unusually dirty even after rain, you can rinse them down gently. Avoid brushes and clearing snow, as both can scratch the panels and void the warranty. For housing co-operatives and jointly owned properties we offer a service agreement with an annual inspection.

An inverter converts the direct current (DC) from the solar panels into the alternating current (AC) that the grid uses. Its size depends on the output of the installation. Cables run from the inverter both to the solar array and to the fuse box, which may be inside the building. An inverter can make some noise while producing, and its placement is subject to several fire-safety requirements. Our installers will help you find the best position when they fit the panels.

We supply solar panels in different sizes and power ratings from several manufacturers, and choose the panel to suit each project. Today we use panels from LONGi, Tongwei, AIKO and JA Solar. We weigh performance, the roof structure and how the building is used to find the best solution.

Panel size varies between manufacturers and generally increases with the panel’s output. Smaller panels are usually around 1.7 metres tall, while larger panels for industrial buildings can be up to 2.4 metres. We choose the panel to suit each project.

The panels can take a great deal of snow. In areas with heavy snowfall we fit an extra rail beneath the panels so they do not break under the snow load. The project manager assesses this before installation.

The wind load is calculated for every installation to NS-EN 1991-1-4 with the Norwegian national annex, wherever the building stands. The reference wind velocity for the municipality, the terrain category and the height of the building all go into the calculation, and height matters a great deal: the roof of a six-storey block takes a considerably higher wind load than the roof of a terraced house in the same street. The roof surface is also divided into zones, and uplift in the corners and along the edge is several times greater than in the middle. That is where we add ballast or fix the installation mechanically. The terrain category is determined from map data, not by judgement; read how.

A turnkey system from us includes everything: grid notification, engineering and design, mounting, protection, commissioning, AC connection and final documentation.

The surplus is sold to your electricity supplier under the agreement you have with them, and the terms vary between suppliers. If the installation can export more than 100 kW to the grid, you are no longer a plus customer but a producer, and selling the power requires a separate agreement. We establish which category the installation falls into before it is designed.

No. Electricity from the panels always goes first to whatever is drawing power in the building. If the panels produce more than the building uses, the surplus is exported to the grid automatically.

Solar panels always generate something as long as they are not covered and daylight is falling on the surface of the panel. In winter there is generally little sun, and snow will cover the panels. We have calculated the seasonal split in our own PV calculator on solkart.no, run on 17.09.2026: in Oslo 97% of the annual output falls between March and October on a flat block roof with panels at 10° facing east and west, and 93% on a south-facing roof pitched at 25°. November to February together account for around 3% on the flat roof. Across the country the share ranges from 91% (Stavanger, south-facing 25°) to close to 100% (Tromsø, flat roof) – the further north, the shorter the season. The assumptions are the same as in our calculator: 5% system losses, crystalline panels, free-standing mounting, a P50 solar year, terrain horizon, and snow and soiling losses included. Shading from neighbouring rows and the surroundings is not included in the figures. You get the figure for the housing co-operative’s own roof in Solsjekk.

All our inverters come with production monitoring in the form of a mobile app. The electrician who commissions the system sets this up and shows you how to use the app.

With an inverter connected to the grid, a power cut causes the inverter to stop supplying electricity. Nor will your own consumption be covered by the panels while the grid is down.

Kilowatt-peak (kWp) is the rated output of each solar panel under standard test conditions (STC). STC sets requirements for temperature, irradiance and angle that are only met occasionally in Norway. Output over the rest of the year is a percentage of the stated kWp. Kilowatt-hours (kWh) are a measure of energy, given by power multiplied by time. A solar panel producing at 1 kW for one hour has produced 1 kWh of electrical energy.

DC stands for direct current, AC for alternating current. Solar panels produce DC. The electricity in buildings and on the grid is always AC, so an inverter is needed to convert DC into AC.