Solar calculator

What it costs, and how long until it pays for itself.

Panels, panels with a battery, or just a battery if you already have panels. The calculator uses the solar radiation where you live, your household's consumption and local energy prices to estimate the cost, the yearly saving and the payback period.

Every assumption used in the calculation is shown at the end, so the result can be checked.

Step 1

What do you want to install?

This choice decides the questions below and the result of the calculation.

Panels only Nothing installed yet. During the day you use what the panels make; in the evening you use the grid. Panels and a battery Nothing installed yet. The battery keeps part of the daytime output for the evening. Battery only You already have panels installed and want to add storage.

Step 2

Where will the panels go?

Where they are mounted changes how many fit and how much the installation costs.

Pitched roof Flat roof or terrace Apartment block roof, through the owners' association Requires a decision by the owners' association. Ground-mounted frame in the garden Canopy or solar carport Apartment, with no access to a roof

Step 3

Where will the system be installed?

Solar radiation is taken from the coordinates of the place, not from the country's name: between the north and the south of one country the difference is more than ten per cent.

Country Region Town or postcode (optional)

Step 4

How much do you use in a month?

Check your last bill. You can enter the consumption in kWh or the amount of the bill.

How much do you use in a month?

The button changes the unit and converts the figure for you.

Price used for the conversion: 0.404 EUR per kWh

Step 5

How much roof can you use?

Enter only the clear area, without chimneys, windows, aerials or shaded parts.

80 m²

Step 6

Which way does the roof face?

South-facing usually produces the most. If you are not sure, choose “I don't know” and we will use a cautious estimate.

Which way does the roof face? How steep is the roof?

On a flat roof, on the ground and under a canopy the angle comes from the frame, not from the building.

The result

Panels and a battery, in Northern and Western

8.7

years to pay for itself

1,613 EUR

estimated saving per year

10,833–18,589 EUR

estimated cost, turnkey

This is an estimate, not a quote. The real price depends on the installer, the roof and the month of installation.

Download the PDF report Would you like a free quote?

Recommended system

Rating

8.6 kWp

Panels

about 19

Produces per year

6,253 kWh

Used on site

41%

Battery

7.5 kWh

Area needed

37 m²

Energy sent to the grid

3,602 kWh

Energy bought from the grid

587 kWh

The recommended rating follows from your consumption, the area available and local production conditions. The rating is limited by your annual consumption.

What the battery adds, against a system without one

Indicator	Without a battery	With a battery
Cost	9,883 EUR	14,711 EUR
Saving per year	1,426 EUR	1,613 EUR
Used at home	24%	41%
Energy from the grid	1,643 kWh	587 kWh
Energy exported	4,775 kWh	3,602 kWh
Payback	6.6 years to pay for itself	8.7 years to pay for itself
Saving over 25 years	33,172 EUR	27,641 EUR

The battery adds 211 EUR a year. Weigh that saving against the difference in price.

The battery does not pay for itself on these figures.It can still be useful: it gives you evening autonomy, it keeps the lights on during an outage if it has the right equipment, and it shelters you from a price rise or a change in the compensation rules.

How long until it pays for itself

Without any grant

8.7

years to pay for itself

We have no programme on record for your country.

Would you like a free quote?

We will put you in touch with an installer in your area. You will get a quote based on the configuration calculated here. Free, with no obligation.

Production and consumption, month by month

In summer production beats consumption; in winter it is the other way round. The rest of the calculation grows out of that gap.

Production
Consumption

See the figures behind the chart

Month	Production	Consumption
Jan	123 kWh	305 kWh
Feb	239 kWh	263 kWh
Mar	497 kWh	273 kWh
Apr	759 kWh	244 kWh
May	943 kWh	239 kWh
Jun	916 kWh	223 kWh
Jul	861 kWh	233 kWh
Aug	773 kWh	233 kWh
Sep	548 kWh	236 kWh
Oct	337 kWh	265 kWh
Nov	168 kWh	282 kWh
Dec	89 kWh	323 kWh

Where the energy produced goes

Used on site, put through the battery, or sent to the grid. Each kilowatt-hour appears in exactly one place.

Used on site
Stored in the battery
Sent to the grid

See the figures behind the chart

Indicator	kWh
Used on site	1,477 kWh
Stored in the battery	1,173 kWh
Sent to the grid	3,602 kWh
Bought from the grid	587 kWh

Balance of the investment, year by year

It starts at minus the cost of the system and climbs with each year's saving. Crossing zero is the moment it pays for itself.

Cumulative balance
Payback point

See the figures behind the chart

Year	Saving per year	Cumulative balance
1	1,613 EUR	-13,099 EUR
2	1,633 EUR	-11,465 EUR
3	1,655 EUR	-9,811 EUR
4	1,676 EUR	-8,134 EUR
5	1,698 EUR	-6,436 EUR
6	1,720 EUR	-4,716 EUR
7	1,743 EUR	-2,974 EUR
8	1,766 EUR	-1,208 EUR
9	1,789 EUR	581 EUR
10	1,813 EUR	2,394 EUR
11	1,837 EUR	4,230 EUR
12	1,861 EUR	6,091 EUR
13	1,886 EUR	7,977 EUR
14	1,911 EUR	9,888 EUR
15	1,937 EUR	11,825 EUR
16	2,031 EUR	8,136 EUR
17	2,057 EUR	10,194 EUR
18	2,084 EUR	12,278 EUR
19	2,111 EUR	14,388 EUR
20	2,138 EUR	16,526 EUR
21	2,166 EUR	18,692 EUR
22	2,194 EUR	20,886 EUR
23	2,222 EUR	23,108 EUR
24	2,252 EUR	25,360 EUR
25	2,281 EUR	27,641 EUR

Battery capacity over time

It falls with degradation and returns when the battery is replaced.

See the figures behind the chart

Year	Battery
1	7.5 kWh
2	7.4 kWh
3	7.2 kWh
4	7.1 kWh
5	6.9 kWh
6	6.8 kWh
7	6.6 kWh
8	6.5 kWh
9	6.4 kWh
10	6.3 kWh
11	6.1 kWh
12	6.0 kWh
13	5.9 kWh
14	5.8 kWh
15	5.7 kWh
16	7.5 kWh
17	7.4 kWh
18	7.2 kWh
19	7.1 kWh
20	6.9 kWh
21	6.8 kWh
22	6.6 kWh
23	6.5 kWh
24	6.4 kWh
25	6.3 kWh

Assumptions used

Below are the values used in the calculation and the source of each one, so the result can be checked.

Assumption	Value	Source
Coordinates used	53.80, -8.60 — Northern and Western	PVGIS PVGIS-SARAH3 · 2026-09-13
Specific yield of the location	817 kWh/kWp	PVGIS PVGIS-SARAH3 · 2026-09-13
Orientation used	90°	PVGIS PVGIS-SARAH3
Tilt used	30°	PVGIS PVGIS-SARAH3
Temperature, spectral and incidence-angle losses	9.7%	PVGIS PVGIS-SARAH3 · 2026-09-13
Price of energy on the bill	0.404 EUR/kWh	Eurostat nrg_pc_204, 2025-S2
Price of energy sent to the grid	0.184 EUR/kWh — I don't know	Eurostat nrg_pc_204, 2025-S2
Consumption you entered	3,120 kWh per year	entered by you
System efficiency	89.5%	EuroEnergy.live estimate
System losses	System losses: 10.5% · inverter 2.5% · cabling 1.5% · soiling 2.0% · mismatch 1.5% · shading 3.0%	EuroEnergy.live estimate
Reference panel	450 Wp · 2.0 m²	EuroEnergy.live estimate
Annual panel degradation	0.5%/an	EuroEnergy.live estimate
Lifetime	25 years	EuroEnergy.live estimate
Assumed energy price growth	2.0%/an	EuroEnergy.live estimate
Annual maintenance	0.5%	EuroEnergy.live estimate
Evening and night consumption	47.6%	EuroEnergy.live estimate
Shape of the consumption day	peak at 19:00	EuroEnergy.live estimate
Mounting type	Pitched roof	entered by you
Usable area	90.0% · 4.3 m²/kWp	EuroEnergy.live estimate
Battery round-trip efficiency	90.0%	EuroEnergy.live estimate
Usable battery capacity	6.8 kWh (90.0%)	EuroEnergy.live estimate
VAT	23.0%	EuroEnergy.live — interval european de referință, neverificat
estimated cost, turnkey	10,833 EUR – 18,589 EUR	EuroEnergy.live — interval european de referință, neverificat · unverified