Any company can embed this calculator on its own website, free of charge, as a simplified version for their clients. Generate a ready-to-use, branded embed code right on this page (section 2 below). For companies that prepare quotes and sell installations professionally, we recommend using the full EasySolar platform instead, available at web.easysolar-app.com.

Table of Contents

1. Try the calculator
2. Add this calculator to your website
3. How the PV system sizing works
4. What to pay attention to
5. Example calculation
6. Simplified vs. full version

1. Try the calculator

2. Add this calculator to your website

Installers and distributors are welcome to embed the calculator on their own pages, free of charge. Pick your market's language and enter your company name below, the embed code is generated automatically, ready to copy into your site.

Condition of use: embedding this calculator on your own website is permitted only if the built-in EasySolar attribution section (the footer inside the calculator, reading "Calculator provided by EasySolar AI…" together with the EasySolar AI logo and link) stays visible and unmodified. Do not hide it with CSS, crop it out of the iframe, or edit its text or link. Removing or altering this section revokes permission to use the calculator on your site.

Generate your embed code

3. How the PV system sizing works

The calculator walks through three steps, and every number on screen is derived — nothing is hard-coded. Here is the full chain, in the order the calculator computes it.

Step 1 — From the bill to annual consumption

You either pick one of the three house presets or type your monthly bill directly. Whichever you touched last is the one that leads:

annual_kWh   = (monthly_bill × 12) / energy_price
monthly_bill = annual_kWh × energy_price / 12
daily_kWh    = annual_kWh / 365

Picking a preset sets annual consumption and recalculates the bill. Editing the bill by hand takes over the other way round, and the preset stops driving the number. The energy price is pre-filled per market and can be overwritten.

Step 2 — PV system sizing from the number of panels

system_kWp        = panel_count × 450 Wp / 1000
daily_production  = system_kWp × yield_per_kWp_per_day
coverage_percent  = min(daily_production / daily_consumption × 100, 100)

yield_per_kWp_per_day is the annual average for your market, taken from PVGIS (PVGIS-SARAH2, 1 kWp, 14% system loss) and shared with our panel orientation calculator, so both tools agree:

Step 3 — From appliances to storage capacity

total_load_W  = sum of the wattage of the selected appliances
capacity_kWh  = total_load_W × hours_of_autonomy / 1000
module_count  = max(1, ceil(capacity_kWh / 5 kWh))

One storage module is 5 kWh, drawn as five segments of 1 kWh each. Modules fill from the first one up, so the last battery on screen always shows the remainder. Deselecting every appliance gives 0 kWh and one empty module — never an error.

The appliance loads used are indicative:

4. What to pay attention to

This is a marketing estimator, and it is deliberately simple. These are the places where it departs from a real design, and they matter when you read the result:

• Coverage is an annual average, not an hourly balance. Production and consumption are compared as yearly totals divided by 365. A real system produces three to four times more in July than in December, so a system showing "100% coverage" here still imports from the grid on winter evenings.
• Self-consumption and export are not separated. Every kilowatt-hour produced counts towards coverage, even the ones exported at noon while nobody is home. Actual self-consumption for a household without storage is typically 25–40%.
• Coverage is capped at 100%. Oversizing beyond annual consumption stops moving the bar, because the model has no way to value the surplus without a local billing scheme.
• Irradiation is a country-level archetype, not your address. Roof pitch, azimuth, shading from trees and chimneys, and snow cover are not modelled here. Orientation alone can move the yield by more than 40%.
• Storage capacity is nameplate, not usable. The model multiplies load by hours. It ignores depth of discharge, inverter and conversion losses, degradation, and the fact that a heat pump or an EV charger cannot usually run off a home battery at full power.
• Appliances are assumed to run continuously. A fridge draws its rated power in bursts, not around the clock, so a real backup lasts longer than this arithmetic suggests for cycling loads, and shorter for anything with a startup surge.
• Prices and consumption presets are market averages. They are starting points for the sliders, not a tariff lookup.

The full EasySolar platform replaces every one of these with the real thing: hourly simulation, address-level irradiation, the actual roof, and real equipment datasheets.

5. Example calculation

Walking through the defaults the calculator opens with, on the Polish market (?lang=pl): the medium house preset, 12 panels, four hours of autonomy, and fridge + lighting + router selected.

Step 1 — consumption

preset "medium house"  = 4 000 kWh / year
energy price           = 1.00 PLN / kWh
monthly bill           = 4 000 × 1.00 / 12   = 333 PLN
daily consumption      = 4 000 / 365         = 11.0 kWh

Step 2 — system size and coverage

system size      = 12 × 450 / 1000           = 5.40 kWp
daily production = 5.40 × (1 048 / 365)      = 15.5 kWh
coverage         = min(15.5 / 11.0 × 100, 100) = 100%

Annual production, 5 659 kWh, exceeds the 4 000 kWh the house uses, so the bar is full. Read that as "a year's worth of energy", not as "no more electricity bills" — see the first two points in section 4.

Step 3 — storage

load     = 150 (fridge) + 100 (lighting) + 50 (router) = 300 W
capacity = 300 × 4 / 1000                              = 1.2 kWh
modules  = max(1, ceil(1.2 / 5))                       = 1 module (1 of 5 segments lit)

Add the EV charger (3 700 W) and stretch autonomy to ten hours and the same arithmetic gives 40 kWh, or eight modules — which is the point of the exercise: it shows a client immediately which appliance is the expensive one to keep alive.

6. Simplified vs. full version

The calculator on this page is a static, simplified model. It is built to give you an intuition for the numbers, not a final quote.

The full version is EasySolar, available after registration at web.easysolar-app.com. It designs the actual installation:

• PV layout on satellite and drone imagery of the real roof, with shading analysis,
• irradiation data for the exact address, not a country average,
• real equipment: panels, inverters and storage from manufacturer databases,
• financial analysis with local tariffs and financing,
• and a complete interactive offer you can send to your client in minutes, viewable in the browser, tracked, and ready to sign.

Create a free EasySolar account and turn this estimate into a real offer →