An on-site solar power plant reduces Scope 2 emissions by the amount of grid electricity it displaces, multiplied by the grid emission factor. A battery energy storage system (BESS) increases this effect by shifting surplus daytime generation to the evening, but it introduces losses of its own. That is why you need to count not the solar plant's output but the actual drop in electricity purchased from the grid.
Baseline and project
- Baseline: all of the facility's electricity is bought from the grid.
- Project: part of the demand is covered directly by the solar plant, part by the battery and the rest by the grid.
Reduction = (Grid_elec_baseline − Grid_elec_project) × EF_grid
Solar output and the drop in purchases are not the same thing: surplus that the facility neither consumed nor stored does not reduce its purchases. Exporting surplus to the grid is a separate matter, governed by the methodology and contract terms, and it is not automatically part of the facility's own reduction.
Why an hourly balance is needed
The sun generates during the day, while the facility's load is spread around the clock. Monthly totals hide surpluses: in May a solar plant may generate more than the facility uses at midday yet less than its monthly consumption. A correct calculation runs over the 8,760 hours of the year: for each hour, generation is compared with load, and self-consumption, battery charging and discharging, and grid purchases are determined.
Worked example
For this example, we take a grid emission factor of 0.726 kg CO₂e/kWh (an estimated value).
Baseline: the facility buys 1,200,000 kWh a year.
- 1,200,000 × 0.726 = 871,200 kg = 871.2 t CO₂e.
Project without storage: the solar plant generated 400,000 kWh; according to the hourly balance, self-consumption was 330,000 kWh and surplus 70,000 kWh.
- Grid purchases: 1,200,000 − 330,000 = 870,000 kWh × 0.726 = 631.6 t.
- Reduction: 871.2 − 631.6 = 239.6 t CO₂e.
Project with storage: the BESS takes in 60,000 kWh of surplus and delivers 54,000 kWh to the facility (the example assumes charge–discharge losses of 6,000 kWh; in a real project, use monitoring data).
- Grid purchases: 1,200,000 − 330,000 − 54,000 = 816,000 kWh × 0.726 = 592.4 t.
- Reduction: 871.2 − 592.4 = 278.8 t CO₂e.
The battery added 39.2 t of reductions. If, however, the battery charges from the grid at night, its losses increase purchases and emissions — this mode of operation must be reflected separately in the calculation.
Which grid factor to use
In corporate reporting, Scope 2 is calculated with two methods — location-based and market-based (see Scope 2: two methods). For a climate project, the factor is set by the methodology. For the Article 6.4 mechanism, Gold Standard Tool 10 v1.0 (August 27, 2026) describes how to calculate the grid factor: annual data with a 10% discount, a 24-month lag and separate criteria for renewables with storage. Check the specific values for Uzbekistan and Belarus in regulatory documents.
Solar combined with a heat pump
Solar plants complement heat pumps well: on-site generation cuts the emissions from their electricity use. But the same drop in grid purchases cannot be claimed twice — as the effect of both the solar plant and the heat pump. The calculation must be based on a single electricity balance for the facility.
How it works in the platform
- The MRV contour is still in development and is marked “Soon” in the platform: project calculations for solar and storage with an hourly balance and a baseline-versus-project comparison are not yet available in it.
- In the GHG contour, you can already account for an on-site solar installation: in Data entry, solar generation is entered month by month for the facility, and purchased electricity is entered through connections and meters, with invoices and photos of meter readings attached. Keep in mind that these data are monthly: a project calculation over 8,760 hours requires hourly data from the meters.
- The platform shows Scope 2 as two results — “Location-based” and “Market-based”; facility totals and monthly trends are on the company GHG page.
Frequently asked questions
Why is the reduction smaller than solar output × emission factor?
Because part of the output is surplus that did not reduce grid purchases. In the example, output was 400,000 kWh, but without storage purchases fell by only 330,000 kWh.
Does a battery reduce emissions on its own?
No. It reduces emissions only when it stores energy that would otherwise be lost or replaced by grid purchases. Battery losses always reduce the effect.
Can I sell the reductions from a solar plant and also show them in my own Scope 2?
No, that is double counting: if the reductions have been transferred to a buyer as carbon units, you cannot claim them in your own reporting without qualification.