Enter the address, how much electricity the house uses a year or a month and what matters more to you: saving or power during outages. The calculator picks the plant size, the number of panels, the area, the inverter type and the batteries, and shows what the plant makes each month according to PVGIS.
In short: the plant size in kW is the yearly consumption in kWh divided by what 1 kW of panels makes a year at your address (it depends on the region, the tilt and the direction). For a typical house using 4,000 kWh a year in Kyiv that is about 4 kW, i.e. 7 panels of 550 W.
How it is calculated
What 1 kW of panels makes at your address comes from PVGIS 5.3 (EU Joint Research Centre): a typical year built from many years of hourly data — the same as in the payback calculator. If PVGIS does not answer, the Solispec designer's formula is used. The consumption is spread over the hours by the typical profile of the chosen house type — an assumption, not measured data. The upper end of the range is the plant that makes in a year what the house uses in a year; the lower end is the largest plant that in no month makes more than the house uses that month. Two sizes are shown: «covers the whole yearly consumption» — the upper end rounded up to whole panels, recommended if the surplus is sold to the grid; «for self-consumption» — the largest plant whose hour-by-hour balance over the year (with the batteries, if any) keeps at least half of the last added panel's output in the house, recommended if the surplus is not sold. The goal «saving» means a grid inverter without batteries (a grid inverter takes no batteries). «Backup» or «both» means a hybrid inverter and the fewest batteries that last the given hours at the given load: usable energy = capacity × depth of discharge × 90 % efficiency, as in the backup calculator. Roof area: the panels side by side with a 20 mm gap. On the ground: one row of tables two panels high at the best tilt for the year; for several rows, the distance at which the rows do not shade each other on 21 December from 10:00 to 14:00. A price is shown only from real prices, otherwise not at all.
The calculation is preliminary. A qualified engineer must check it before installation. Codes: DBN V.1.2-2:2006 (Ukraine) and the Eurocode; for other countries — snow and wind values from the national annex, entered by hand.
Frequently asked questions
How many kW of solar does a house need?
Divide the yearly consumption (kWh, on your electricity bills) by what 1 kW of panels makes a year at your address. The calculator takes that figure from PVGIS. For a typical house using 4,000 kWh a year in Kyiv it comes to about 4 kW.
How many solar panels does a house need?
Divide the size you need by the power of one panel and round up: 3.85 kW is 7 panels of 550 W. Choose your panel model and the calculator recounts the number and the area.
Which inverter: grid-tied or hybrid?
If you only want to save, a grid inverter is enough: it works while the grid is on, and batteries cannot be connected to it. If you need power during outages, take a hybrid inverter with batteries.
What battery capacity for outages?
Multiply the power of what has to keep running (fridge, lights, router, boiler pump) by the hours without power and add a margin for the depth of discharge and the losses. The calculator does this and picks the number of batteries of the chosen model.
Why does the calculator show no price?
We show a price only from real data: an installer's prices or dated aggregate prices from estimates. Until there are such data we do not make one up. An installer makes the exact estimate in the Solispec designer.
Ground frame designer
Design the ground frame for your solar plant
The calculator’s values go to the designer: then the frame, the DBN checks and the estimate.
Not sure about the consumption? Check your electricity bills. If the field is empty, we take 4,000 kWh a year — a typical family house.
Roughly: fridge ≈ 150 W, router ≈ 20 W, LED lights ≈ 50 W, boiler pump ≈ 100 W, laptop ≈ 60 W, TV ≈ 100 W. Add what runs at the same time.
Recommended size3.85 kW
Range1.65–3.85 kW
Panels7 × 550 W
Roof area≈ 19 m²
InverterHybrid
Batteries1 pcs, 5.12 kWh — 8.3 h
Output per year4,224 kWh
For self-consumption
If the surplus is not sold: the house uses almost everything the plant makes.
Size
2.2 kW
Panels
4 × 550 W
Output per year
2,414 kWh
Used at home
≈ 95 % of the output
Surplus to the grid a year
111 kWh
Covers the whole yearly consumptionRecommended
If the surplus is sold to the grid: in a year the plant makes what the house uses.
Size
3.85 kW
Panels
7 × 550 W
Output per year
4,224 kWh
Used at home
≈ 68 % of the output
Surplus to the grid a year
1,340 kWh
«For self-consumption» is the largest plant whose hour-by-hour balance over the year (with the batteries, if any) keeps at least half of the last added panel's output in the house.
The range in panels: from 3 (almost everything made is used at home) to 7 (in a year the plant makes what the house uses).
A hybrid inverter powers the house from the batteries when the grid is off and charges them from the panels.
Deye SE-G5.1 Pro-B · 5,12 kWh: this many last 4 h at a 500 W load at night, without help from the panels.
Over a year the plant covers 69 % of the house's consumption, and 65 % of its output is used at home; 1,340 kWh go to the grid.
Asking PVGIS… · 1,097 kWh/kWp
No price shown: we give one only from real prices (your installer's prices in Solispec Pro or dated aggregate prices from estimates). We do not make prices up.
The plant's output by month (bars) and the house's consumption (outline), kWhBy month