{"id":4600,"date":"2026-10-07T12:44:02","date_gmt":"2026-10-07T10:44:02","guid":{"rendered":"https:\/\/www.solareatech.com\/?p=4600"},"modified":"2026-10-07T12:44:04","modified_gmt":"2026-10-07T10:44:04","slug":"how-to-calculate-your-self-consumption-photovoltaic-system-step-by-step-guide","status":"publish","type":"post","link":"https:\/\/www.solareatech.com\/en\/how-to-calculate-your-self-consumption-photovoltaic-system-step-by-step-guide\/","title":{"rendered":"How to Calculate YOUR Self-Consumption Photovoltaic System: Step-by-Step Guide"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">Knowing <strong>how to calculate your self-consumption photovoltaic system<\/strong> is the difference between a solar installation that saves you money and one that is too small to matter or too big to pay off. The good news: the maths is simple. You need five numbers, a calculator and about twenty minutes. This guide walks you through each step with a worked example for a typical home in the Alicante province, so you can run your own figures before asking anyone for a quote.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>The short answer<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">To size a self-consumption photovoltaic system:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Find your <strong>annual electricity consumption<\/strong> (kWh) on your bills.<\/li>\n\n\n\n<li>Look at <strong>when<\/strong> you use it (day vs. night).<\/li>\n\n\n\n<li>Divide the consumption you want to cover by your location&#8217;s <strong>yearly yield per kWp<\/strong> to get the system size in kWp.<\/li>\n\n\n\n<li>Divide that size by the <strong>panel wattage<\/strong> to get the number of panels.<\/li>\n\n\n\n<li>Check your <strong>roof space, orientation and shading<\/strong>, then estimate savings and payback.<\/li>\n<\/ol>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Step 1: Find your annual consumption<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Look at your last 12 months of bills, or log in to your distributor&#8217;s customer area, and add up the kWh. Annual figures matter more than a single month, because summer air conditioning and pool pumps can double your usage.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Example:<\/strong> a family home in Alicante consuming <strong>4,500 kWh per year<\/strong>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Step 2: Understand when you consume<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Solar panels only produce during daylight. The share of your production that you use directly in the home is your <strong>self-consumption ratio<\/strong>, and it drives most of your savings, because energy you use directly is worth much more than energy you send to the grid.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Home occupied during the day (remote work, retirees, pool, air conditioning): higher direct use.<\/li>\n\n\n\n<li>Home empty from morning to evening: more surplus, lower direct use.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\">As a rough guide, systems without a battery often use only a minority-to-half of what they produce directly; a battery or shifting loads (water heater, dishwasher, washing machine, EV charging) to midday raises that figure. This is the number worth discussing in a real technical study, because it depends on your habits.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Step 3: Calculate the system size in kWp<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Formula:<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>System size (kWp) = Annual consumption to cover (kWh) \u00f7 Yearly yield per kWp (kWh\/kWp)<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">In the Alicante area, a well-oriented, unshaded system typically produces in the order of <strong>1,500 kWh per kWp per year<\/strong> (an orientative figure: orientation, tilt, shading and equipment change it).<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Example:<\/strong> to cover all 4,500 kWh: 4,500 \u00f7 1,500 = <strong>3 kWp<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Do you want to cover 100%? Not necessarily. Because surplus energy is compensated at a lower price than the one you pay for energy you buy, many homes aim to cover a large share of their consumption rather than oversizing. Plan ahead too: an electric car, a heat pump or a new pool will raise your consumption and justify a bigger system now.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Typical residential systems fall between <strong>3 and 8 kWp<\/strong>.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Step 4: Calculate the number of panels<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Formula:<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Number of panels = System size (W) \u00f7 Panel power (W)<\/strong><\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Example:<\/strong> 3,000 W \u00f7 550 W = 5.5, so round up to <strong>6 panels of 550 W = 3.3 kWp<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Higher-wattage panels mean fewer panels for the same kWp, which matters if roof space is limited. Remember that panel power and panel efficiency are different things: efficiency tells you how much power you get per square metre.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Step 5: Check your roof<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">The calculation only works if the panels fit and receive sun. Check:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Surface:<\/strong> a 550 W panel takes roughly 2.6 m\u00b2, so 6 panels need about 15\u201316 m\u00b2 of usable roof (plus space for access and spacing).<\/li>\n\n\n\n<li><strong>Orientation:<\/strong> south is ideal; south-east and south-west lose only a little.<\/li>\n\n\n\n<li><strong>Tilt:<\/strong> a moderate tilt works well in Spain.<\/li>\n\n\n\n<li><strong>Shading:<\/strong> chimneys, aerials, parapets and neighbouring buildings can cost more production than the difference between two panel brands.<\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Step 6: Estimate production, savings and payback<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Estimated production:<\/strong> 3.3 kWp \u00d7 1,500 = about <strong>4,950 kWh per year<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Illustrative savings<\/strong> (assumptions: 40% used directly, 60% sent to the grid; you pay around 0.18 \u20ac\/kWh; surplus compensated around 0.07 \u20ac\/kWh):<\/p>\n\n\n\n<figure class=\"wp-block-table\"><table class=\"has-fixed-layout\"><tbody><tr><td><strong>Item<\/strong><\/td><td><strong>Calculation<\/strong><\/td><td><strong>Result<\/strong><\/td><\/tr><tr><td>Energy used directly<\/td><td>4,950 \u00d7 40% = 1,980 kWh \u00d7 0.18 \u20ac<\/td><td>\u2248 356 \u20ac<\/td><\/tr><tr><td>Surplus compensated<\/td><td>4,950 \u00d7 60% = 2,970 kWh \u00d7 0.07 \u20ac<\/td><td>\u2248 208 \u20ac<\/td><\/tr><tr><td><strong>Total yearly saving<\/strong><\/td><td><\/td><td><strong>\u2248 564 \u20ac<\/strong><\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Estimated cost:<\/strong> installed residential systems are commonly in the range of <strong>1,000\u20131,500 \u20ac per kWp<\/strong>. For 3.3 kWp, at about 1,250 \u20ac\/kWp, that is roughly <strong>4,100 \u20ac<\/strong>.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Payback:<\/strong> 4,100 \u00f7 564 = about <strong>7 years<\/strong> before any tax relief. With the personal income tax (IRPF) deduction (40% of the cost, up to 3,000 \u20ac, when its conditions are met) and municipal rebates on IBI and ICIO, the real payback falls noticeably, and a higher direct-use ratio shortens it further.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><em>All prices and tariffs in this example are illustrative. Your real figures depend on your tariff, your usage pattern and the final quote. Solar subsidies change often; check our guide to solar panel subsidies in Alicante for what is currently open. The Next Generation EU funds are closed to new applications.<\/em><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Should you add a battery to the calculation?<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">A battery is optional. It raises your self-consumption by storing midday surplus for the evening, and can provide backup during blackouts, but it adds cost. A common approach is to calculate the system without a battery first, then test whether the extra self-consumption justifies the investment. Many homes start without one and leave the installation ready to add it later.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Common mistakes when calculating a self-consumption system<\/strong><\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Using one month&#8217;s bill<\/strong> instead of 12 months.<\/li>\n\n\n\n<li><strong>Ignoring daily consumption timing<\/strong>, which sets your real savings.<\/li>\n\n\n\n<li><strong>Oversizing<\/strong> just to cover 100% when surplus is paid at a lower price.<\/li>\n\n\n\n<li><strong>Ignoring shading<\/strong> and roof orientation.<\/li>\n\n\n\n<li><strong>Forgetting future consumption<\/strong> (EV, heat pump, pool).<\/li>\n\n\n\n<li><strong>Counting subsidies that no longer exist.<\/strong><\/li>\n<\/ul>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Frequently asked questions<\/strong><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>How do I calculate the size of my self-consumption photovoltaic system?<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Divide the annual consumption you want to cover (kWh) by the yearly yield per kWp for your location. In the Alicante area, around 1,500 kWh\/kWp is a reasonable orientative figure.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>How many solar panels do I need for a house?<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Divide the system size in watts by the power of each panel. For example, 3,300 W of system with 550 W panels means 6 panels. Typical homes use between 3 and 8 kWp.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>How much does a residential self-consumption system cost?<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">As a general market reference, installed systems range from about 1,000 to 1,500 \u20ac per kWp, before tax deductions and municipal rebates. A real quote depends on the roof, equipment and whether a battery is included.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>How long does a self-consumption system take to pay for itself?<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">In the Alicante province, typical payback ranges from 5 to 7 years, depending on how much of your production you use directly and on the incentives you can apply.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Can I do this calculation myself?<\/strong><\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">Yes, the steps above give a solid estimate. A technical study then refines it with your real consumption profile, roof measurements and shading analysis.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Get your system calculated by professionals<\/strong><\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">Solarea Tech has completed more than 500 installations in the Alicante province, with our own technical team and a 5.0\/5 rating on Google from over 129 reviews. Send us your bills and we will size your system, check your roof and give you a clear proposal, including the incentives that apply in your town. For typical prices, see our guide to how much solar panels cost in Spain.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\ud83d\udc49 <a href=\"https:\/\/www.solareatech.com\/en\/contact\/\">Request your free quote in English<\/a> and we will get back to you within 24 hours.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">\ud83d\udcde 669 34 86 07<\/p>\n","protected":false},"excerpt":{"rendered":"<p>Knowing how to calculate your self-consumption photovoltaic system is the difference between a solar installation that saves you money and one that is too small to matter or too big to pay off. The good news: the maths is simple. You need five numbers, a calculator and about twenty minutes. This guide walks you through [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":4601,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-4600","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-sin-categorizar"],"acf":[],"_links":{"self":[{"href":"https:\/\/www.solareatech.com\/en\/wp-json\/wp\/v2\/posts\/4600","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.solareatech.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.solareatech.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.solareatech.com\/en\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/www.solareatech.com\/en\/wp-json\/wp\/v2\/comments?post=4600"}],"version-history":[{"count":0,"href":"https:\/\/www.solareatech.com\/en\/wp-json\/wp\/v2\/posts\/4600\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.solareatech.com\/en\/wp-json\/wp\/v2\/media\/4601"}],"wp:attachment":[{"href":"https:\/\/www.solareatech.com\/en\/wp-json\/wp\/v2\/media?parent=4600"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.solareatech.com\/en\/wp-json\/wp\/v2\/categories?post=4600"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.solareatech.com\/en\/wp-json\/wp\/v2\/tags?post=4600"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}