Anyone can see the panels. The rest is what we do.
Hybrid solar PV systems with battery storage for houses in north-east Bulgaria. The inverter, the battery, the consumer unit and the paperwork for the municipality and the grid operator are the rest — and we show you all of it before the quote, not after.
9 panels + 10.2 kWh batterythe cheapest system that covers 80% of the electricity in a house using 4,500 kWh a year — 81% in an hour-by-hour simulation; 9 × 440 W = 4 kW, 6 kW hybrid inverter; the same panels without a battery — 39%Pays back in ≈ 16.3 yearsat today's electricity prices and price list, with panel degradation factored in; replacing the inverter and battery is shown separately — in the calculatorNo selling to the gridthe system covers the house and charges the battery — it produces nothing beyond thatUp to 20 kWno building permit for an existing single-family house, for self-consumption — we file the notification
24 months installation warranty; panels — manufacturer's warranty, usually 25 years on outputinverter on a wall, never on the roofroof hooks spaced for your site's windnotifications to the municipality and grid operatortest report
System cross-section9 panels × 440 W · 6 kW inverter · 10.2 kWh battery
1The panels — 9 × 440 Wcan produce up to ≈ 5,280 kWh a year on a south-facing roof in Varna; they produce as much as the house and battery can take. Fixed on hooks under the tiles, closer together at the edges — that's where the wind rips them off
2The inverter — 6 kW hybrid, on the walla non-combustible wall in a garage or plant room; never on the roof, never in salty air
3The battery — 10.2 kWh, on the floorstores the midday power for the evening; most models expand with 5.12 kWh modules. Around 100 kg: not in a bedroom, not on an escape route
5The grid — for buying onlywhen the roof and battery aren't enough: at night and in winter. Nothing is fed back into it
§The paperworknotification 14 days before, declaration after, grid operator under Art. 25a — we file them all
01Which system you need
How many panels, which battery — and when you get your money back.
Tell us how much you pay for electricity, which way your roof faces and how much of your power you want it to supply. The calculator finds the cheapest mix of panels and battery that gets there — hour by hour over a full year, cloudy days included — and shows what it costs and how many years it takes to pay back. Then adjust it yourself: each step shows what it brings.
1How you live
€
≈ 4,500 kWh a year · 12.3 kWh a day
3The roofwhich way the slope facestilt
Slope facing S, tilt 30–35°: 100% of the optimum (south, 30–35°). One panel gives up to ≈ 587 kWh a year.
dimensions, if you know them
×m
along the eaves × up the slope; without dimensions — up to 45 panels
4More, if you knowtariff · town · supply
tariff
where the house is
mains supply
contracted capacity
kW in your electricity contract
→How much of your power it should cover averaged over the year — energy, not every day
for each target, the cheapest system that reaches it; the rest is bought from the grid, at night and in winter
the cheapest system covering 80%9 panels + 10.2 kWh battery · 6 kW inverter4 kW of panels · single-phase hybrid · battery in 5.12 kWh modules
covers on average81%of your electricity over the year, on average — energy, not every day. Dec 53%, Aug 100% — monthly averagessaves per year€5643,633 kWh of your 4,500 covered by the system, at €0.155 per kWh; your bill drops from €698 to ≈ €135 a yearguide price≈ €8,850incl. VAT, at today's catalogue prices: equipment, mounting and panel installation, electrical package with boards and commissioning, battery, design and paperwork — the quote after the site visit makes it exactpays back in16.3 yearsat today's electricity price, with no replacements; including a new inverter (year 10) and battery (year 12) — in profit for good after 24.1 years
Another 9 points — up to 90% — cost €2,100 more (17 panels + 10.2 kWh); payback becomes 18.3 years One step down: 61% for ≈ €6,600 (6 panels + 5.1 kWh), payback 16 years
±Adjust it yourself — the suggested one for 80%
panels
9
4 kW· 9 × 440 W · up to 17 for a single-phase hybrid
battery
10.2 kWh
5.12 kWh modules · without it, the same panels cover 39%
inverter6 kWhybrid, single-phase — the smallest one where the panels are at most 20% above its rating and 30% above its DC input
iDetailsby month · the roof · where the power goes · how it's calculated
9 panels on the slope facing south100% of the optimum (south, 30–35°) · panel area ≈ 18 m²
weakest · strongest month53% · 100%Dec · Aug — monthly averagefrom 9 panels · 4 kWup to 5,280 kWh3,633 used at home · 1,441 not generatedyou buy from the grid867 kWhat night and in winter · ≈ €135 a yearbattery10.2 kWhwithout it, the same panels cover 39%
By month — monthly averages, not every single day. The percentage is the total energy for the whole month. On a rainy day the battery runs out and the grid takes over — even if the month shows 100%.
straight from the rooffrom the batterybought from the grid
Jan 58%
Feb 60%
Mar 82%
Apr 93%
May 97%
Jun 100%
Jul 97%
Aug 100%
Sep 95%
Oct 89%
Nov 56%
Dec 53%
Coverage 81% over the year: Dec 53%, Aug 100%. From December to February, 533 kWh comes from the grid — 43% of winter consumption.
How it's calculated: for each target we look for the cheapest combination — from 6 panels (the shortest string for a single-phase hybrid) up to 17 (the limit: the roof, twice the contracted capacity, the hybrid's DC input, 45 panels), a battery in 5.12 kWh modules and an inverter matched to the panels and phases — each run through an hour-by-hour simulation over a full year. Prices are from today's catalogue, incl. VAT.
This is a scenario based on a statistical consumption profile and a typical solar year, at today's catalogue prices. Your monthly bills, the site visit and the design refine it — and the quote sets the exact price including installation, consumer unit and paperwork.Get an exact price
02Packages
Three ready-made systems — based on how you live.
Worked out the same way as the calculator: for each type of house, the cheapest system that covers 80% of the electricity, on a south-facing roof in Varna. Your bill and your roof will change the numbers — that's why the calculator is above. Prices are from today's catalogue, incl. VAT; the quote after the site visit makes them exact.
for a small household6 panels + 5.1 kWh battery1–2 people, water heater · about 2,500 kWh a year · bill ≈ €32 a month · single-phase supply
83% of your electricity comes from the roof and battery, averaged over the year; 17% is bought in — at night and in winter (Dec 58%, Jun 100%)
guide price≈ €6,600with installation, consumer unit and paperwork, at today's catalogue prices; the quote after the site visit makes it exact
pays back in21.5 yearsat today's electricity price; with replacements it doesn't move into profit for good within 25 years
Electricity bill: €388 → ≈ €66 a year, €322 saved.
for a family house9 panels + 10.2 kWh batterywater heater, air conditioning for cooling · about 4,500 kWh a year · bill ≈ €58 a month · single-phase supply
81% of your electricity comes from the roof and battery, averaged over the year; 19% is bought in — at night and in winter (Dec 53%, Aug 100%)
guide price≈ €8,850with installation, consumer unit and paperwork, at today's catalogue prices; the quote after the site visit makes it exact
pays back in16.3 yearsat today's electricity price; including inverter and battery replacements — in profit for good after 24.1 years
Electricity bill: €698 → ≈ €135 a year, €564 saved.
for an all-electric house30 panels + 25.6 kWh batteryheating by air conditioning too · about 8,000 kWh a year · bill ≈ €103 a month · three-phase supply
80% of your electricity comes from the roof and battery, averaged over the year; 20% is bought in — at night and in winter (Dec 56%, Jun 100%)
guide price≈ €22,700with installation, consumer unit and paperwork, at today's catalogue prices; the quote after the site visit makes it exact
pays back in24.3 yearsat today's electricity price; with replacements it doesn't move into profit for good within 25 years
Electricity bill: €1,241 → ≈ €251 a year, €990 saved.
Every package includes: panels, hybrid inverter, battery, mounting frame, consumer unit with protection devices, installation, paperwork for the municipality and the grid operator, test report and installation passport. Extra, if needed: trenching, roof reinforcement, a capacity increase under your contract, backup power during power cuts — we tell you at the site visit.Get an exact price
03What's included
What you get for the price — line by line.
The price in the calculator and the packages is built from five lines. Here's what's in each one. Anything not listed here is raised at the site visit and written into the quote — it doesn't turn up later.
1Equipmentfrom the catalogue, in the quote
Panels: monocrystalline, 440–450 W; output warranty from the manufacturer, usually 25 years.
Hybrid inverter: single-phase or three-phase, matched to the panel output and your supply. On a wall in a garage or plant room — never on the roof and never in salty air.
Battery: LiFePO4 in 5 kWh modules, on the floor; most models can be expanded later.
2Mounting and panel installation€120 per panel
Tile roof hooks, aluminium rails, mid and end clamps, earthing of the frame.
Hook spacing is calculated for the wind at your site, closer at the edges — that's where panels get ripped off.
The panels are lifted up, laid out and wired into a string; roof cabling runs in UV-resistant flexible conduit.
Flat roof or garden: south-facing frame, no drilling — €130 per panel.
DC board: circuit breaker, surge protection device (SPD), isolator. AC board: circuit breaker, 30 mA RCD, SPD.
6 mm² solar cable, earthing, a dedicated circuit from the main consumer unit.
Inverter on the wall, connection, commissioning, set-up for zero export to the grid.
Test report: loop impedance, RCD, insulation, earthing. You keep it.
4Battery€150 per module
Installed in place, battery cable with fuse, communication link to the inverter.
Charging set-up: from the roof, never from the grid.
Power during grid outages for a separate circuit (fridge, lighting, boiler) — if the inverter and wiring allow it; charged separately.
5Design and paperwork€750
Design documents, structural and electrical parts, by a licensed designer — required by law (Spatial Development Act, Art. 151).
Notification to the chief architect of the municipality 14 days before installation.
Notification to the grid operator under Art. 25a of the Renewable Energy Act — with your power of attorney, we file it.
Declaration within 14 days of installation that the system is live and built to the documentation — signed by us as the contractor.
Installation passport: a folder with everything above, the test report and the photos. You'll have it for inspections, the insurer or selling the house.
We checked 20 installers' websites: none of them says they file these documents for you. That's why with us they're a separate line, not small print.
−Extra, if neededconfirmed at the site visit
Trenching and cable to an outbuilding.
Roof reinforcement, replacing tiles under the panels.
Replacing the main consumer unit or increasing the contracted capacity under your contract.
Backup power during power cuts (separate circuit, changeover).
Scaffolding where access is difficult; a second roof slope.
Warranty: 24 months on installation; on equipment — the manufacturer's.
Line prices are from today's price list; the quote after the site visit makes them exact for your roof and your consumer unit.Get an exact price
04How it goes
From three photos to a working system — and the folder at the end.
Seven steps: what we do, what depends on you and how long each one takes. The longest part isn't the installation — it's the 14 days required by law after notifying the municipality.
day 01
Three photos and your bill
The roof from the garden, the consumer unit with the cover open, the spot for the inverter; plus your latest electricity bill. Send them from here or by Viber.
you · 5 minutes
within 24 hours2
Written quote
The system, the price across the five lines, coverage and payback as in the calculator, but with your photos taken into account. No call from a salesperson.
us · within 24 hours
week 13
Site visit
We measure the roof, check the tiles and rafters, the consumer unit and your contracted capacity, and the cable route to the inverter. The quote becomes exact and final.
us · about an hour on site
week 1–24
Design and notifications
The designer prepares the structural and electrical parts. We file the notifications to the chief architect and the grid operator with your power of attorney.
us · the law requires 14 days before installation
weeks 3–45
Installation
Frame and panels on the roof, inverter on the wall, battery on the floor, DC and AC boards. Panels in one day, electrics in another; a large three-phase system — up to three.
us · 1–3 days
same day6
Commissioning and testing
Set-up for zero export, protection checks, test report. We show you the inverter app: what the roof is producing, what's in the battery.
us · about 2 hours
within 14 days after7
Declaration and passport
We sign the declaration to the municipality and the grid operator together. You get the installation passport.
together · 15 minutes
In total: usually 3–5 weeks from the photos to a working system. 24 months warranty on the installation; on equipment, the manufacturer's warranty.Start with three photos
No. The system powers the house and charges the battery; once the house is supplied and the battery is full, the panels simply don't produce any more. Nothing goes into the grid, and no money changes hands for it. Selling electricity is a different set-up — building permit, contract with the grid operator, a different procedure; we do those too, but they're not in this calculator.
That depends on the target you choose: 60, 80 or 90% on average over the year. ‘On average’ means in terms of total energy: in summer it's around 100%, in December 40–60%, and on a rainy day the battery runs out and the grid takes over. The calculation runs hour by hour for a full year, using real cloudy days over the region.
By default, the system shuts down — the grid requires this, so that it doesn't send power into the lines while people are working on them. With a battery and a suitable hybrid inverter we can set up a separate circuit for the fridge, lights and boiler that keeps running without the grid. This is not part of the package and is decided at the site visit.
Up to 20 kW on an existing single-family house, for your own use — no (Spatial Development Act, Art. 151). What's required is a notification to the municipal chief architect 14 days before installation, with design documents from a licensed designer, a notification to the grid operator, and a declaration within 14 days after installation. We file all of this for you, under your power of attorney.
Usually 3–5 weeks from your photos to a working system. The quote comes within 24 hours, the site visit in the first week, then the statutory 14 days after the notification, and installation takes 1–3 days. The longest wait is the law, not us.
Because we calculate it honestly: allowing for the panels' gradual loss of output, at today's electricity price, without selling any surplus, and we show the inverter and battery replacement separately. ‘5–6 years’ usually comes from total generation multiplied by the electricity price, as if every kilowatt-hour gets used. Compare figures on a like-for-like basis and ask how they were worked out.
East and west give around 80–85% of what a south-facing roof does, north 50–60%. The calculator shows this for your orientation and pitch; sometimes the better answer is the other side of the roof, or both sides. The site visit settles it.
The panels sit on a ballasted frame facing south at 15°, with no drilling into the roof. The rows are spaced about 2.8 m apart so they don't shade each other; that's why a flat roof takes fewer panels per square metre. The calculator works it out from the roof's dimensions.
Not necessarily. For a typical house a single-phase hybrid is enough; a bigger system — with electric heating or more than about 15–20 panels — usually needs a three-phase supply and a three-phase system. The calculator asks about your supply and picks an inverter that matches the panels.
A 5 kWh module weighs around 45–50 kg, about the same as a washing machine. It stands on the floor in a dry, cool place — a garage, cellar or utility room; not in a bedroom and not on an escape route. The modules stack on top of each other or sit side by side.
A battery — yes, most models expand with modules from the same series. Panels — up to the inverter's DC input limit (around 30% above its rated power); beyond that the inverter has to be replaced. If you're thinking of expanding, mention it at the site visit — we'll choose an inverter with headroom.
It's the capacity in your electricity supply contract — it's stated there. A system for your own use can be up to twice as large as that (Renewable Energy Sources Act, Art. 25a). If you want more panels, the capacity has to be increased with the grid operator — a separate procedure.
Panels — a manufacturer's performance warranty, usually 25 years, with about 0.4% degradation a year. The inverter usually has a 10-year warranty, the battery 10 years or a set number of cycles. In the payback calculation we include them as replacements in year 10 and year 12, so they don't catch you by surprise.
Schemes for households come up from time to time. We don't include them in the calculation, because they come and go; when one is open, we'll tell you and help with the paperwork. The payback shown on the page is without any subsidy — if you get one, it's a bonus.
An installation passport: the design documents, the notifications with their reference numbers, the declaration, the single-line diagram, the inverter settings, the test report, the photos and the warranty cards. For an inspection, an insurer, selling the house or servicing years later, everything is in one folder.
