diff --git a/lib/HanConfigAp/src/configuration.cpp b/lib/HanConfigAp/src/configuration.cpp
index 0a14ae95..1db4e11b 100644
--- a/lib/HanConfigAp/src/configuration.cpp
+++ b/lib/HanConfigAp/src/configuration.cpp
@@ -8,7 +8,7 @@ bool configuration::hasConfig()
 {
 	bool hasConfig = false;
 	EEPROM.begin(EEPROM_SIZE);
-	hasConfig = EEPROM.read(EEPROM_CONFIG_ADDRESS) == EEPROM_CHECK_SUM;
+	hasConfig = EEPROM.read(EEPROM_CONFIG_ADDRESS) >= 71;
 	EEPROM.end();
 	return hasConfig;
 }
@@ -46,6 +46,7 @@ bool configuration::save()
 	}
 
 	address += saveInt(address, fuseSize);
+	address += saveInt(address, distSys);
 
 	bool success = EEPROM.commit();
 	EEPROM.end();
@@ -73,6 +74,7 @@ bool configuration::load()
 	authUser = 0;
 	authPass = 0;
 	fuseSize = 0;
+	distSys = 0;
 
 	EEPROM.begin(EEPROM_SIZE);
 	int cs = EEPROM.read(address);
@@ -118,6 +120,9 @@ bool configuration::load()
 	if(cs >= 73) {
 		address += readInt(address, &fuseSize);
 	}
+	if(cs >= 74) {
+		address += readByte(address, &distSys);
+	}
 	EEPROM.end();
 	return success;
 }
diff --git a/lib/HanConfigAp/src/configuration.h b/lib/HanConfigAp/src/configuration.h
index 68a142ba..76586eaa 100644
--- a/lib/HanConfigAp/src/configuration.h
+++ b/lib/HanConfigAp/src/configuration.h
@@ -30,6 +30,7 @@ public:
 	char* authPass;
 
 	int fuseSize;
+	byte distSys;
 
 	bool hasConfig();
 	bool isSecure();
@@ -41,7 +42,7 @@ protected:
 
 private:
 	const int EEPROM_SIZE = 512;
-	const byte EEPROM_CHECK_SUM = 73; // Used to check if config is stored. Change if structure changes
+	const byte EEPROM_CHECK_SUM = 74; // Used to check if config is stored. Change if structure changes
 	const int EEPROM_CONFIG_ADDRESS = 0;
 
 	int saveString(int pAddress, char* pString);
diff --git a/src/web/AmsWebServer.cpp b/src/web/AmsWebServer.cpp
index 4cbdd5ab..efa3ea06 100644
--- a/src/web/AmsWebServer.cpp
+++ b/src/web/AmsWebServer.cpp
@@ -39,12 +39,6 @@ void AmsWebServer::setup(configuration* config, Stream* debugger) {
 		print(WiFi.localIP());
 	}
 	println("/");
-
-    if(config->hasConfig() && config->fuseSize > 0) {
-        maxPwr = config->fuseSize * 230;
-    } else {
-		maxPwr = 20000;
-	}
 }
 
 void AmsWebServer::loop() {
@@ -62,13 +56,12 @@ void AmsWebServer::setJson(StaticJsonDocument<500> json) {
 			i2 = json["data"]["I2"].as<double>();
 			i3 = json["data"]["I3"].as<double>();
 
-			if(config->hasConfig() && u1 > 0) {
-				maxPwr = config->fuseSize * u1;
+			if(maxPwr == 0 && config->hasConfig() && config->fuseSize > 0 && config->distSys > 0) {
+				int volt = config->distSys == 2 ? 400 : 230;
 				if(u2 > 0) {
-					maxPwr += config->fuseSize * u2;
-					if(u3 > 0) {
-						maxPwr += config->fuseSize * u3;
-					}
+					maxPwr = config->fuseSize * sqrt(3) * volt;
+				} else {
+					maxPwr = config->fuseSize * 230;
 				}
 			}
 		} else {
@@ -182,6 +175,9 @@ void AmsWebServer::configurationHtml() {
 		for(int i = 0; i<64; i++) {
 			html.replace("${config.fuseSize" + String(i) + "}", config->fuseSize == i ? "selected"  : "");
 		}
+		for(int i = 0; i<3; i++) {
+			html.replace("${config.distSys" + String(i) + "}", config->distSys == i ? "selected"  : "");
+		}
 	} else {
 		html.replace("${config.ssid}", "");
 		html.replace("${config.ssidPassword}", "");
@@ -206,6 +202,9 @@ void AmsWebServer::configurationHtml() {
 		for(int i = 0; i<64; i++) {
 			html.replace("${config.fuseSize" + String(i) + "}", i == 0 ? "selected"  : "");
 		}
+		for(int i = 0; i<3; i++) {
+			html.replace("${config.distSys" + String(i) + "}", i == 0 ? "selected"  : "");
+		}
 	}
 	server.send(200, "text/html", html);
 }
@@ -256,6 +255,15 @@ void AmsWebServer::dataJson() {
 	if(!json.isNull()) {
 		println(" json has data");
 
+		int maxPwr = this->maxPwr;
+		if(maxPwr == 0) {
+			if(u2 > 0) {
+				maxPwr = 25000;
+			} else {
+				maxPwr = 15000;
+			}
+		}
+
 		json["maxPower"] = maxPwr;
 		json["pct"]     = min(p*100/maxPwr, 100);
 		json["meterType"] = config->meterType;
@@ -324,6 +332,8 @@ void AmsWebServer::handleSave() {
 
 	config->fuseSize = (int)server.arg("fuseSize").toInt();
 
+	config->distSys = (byte)server.arg("distSys").toInt();
+
 	println("Saving configuration now...");
 
 	if (debugger) config->print(debugger);
diff --git a/web/configuration.html b/web/configuration.html
index 129b1ff5..d8317e81 100644
--- a/web/configuration.html
+++ b/web/configuration.html
@@ -37,8 +37,18 @@
                 <div class="my-3 p-3 bg-white rounded shadow">
                     <h6 class="border-bottom border-gray pb-2 mb-4">AMS meter</h6>
                     <div class="row form-group">
-                        <label class="col-4">Meter type</label>
-                        <div class="col-8">
+                        <label class="col-6">Distribution system</label>
+                        <div class="col-6">
+                            <select class="form-control" name="distSys">
+                                <option value="" ${config.distSys0}></option>
+                                <option value="1" ${config.distSys1}>IT (230V)</option>
+                                <option value="2" ${config.distSys2}>TN (400V)</option>
+                            </select>
+                        </div>
+                    </div>
+                    <div class="row form-group">
+                        <label class="col-6">Meter type</label>
+                        <div class="col-6">
                             <select class="form-control" name="meterType">
                                 <option value="0" ${config.meterType0} disabled></option>
                                 <option value="1" ${config.meterType1}>Kaifa</option>
@@ -48,8 +58,8 @@
                         </div>
                     </div>
                     <div class="row form-group">
-                        <label class="col-4">Main fuse</label>
-                        <div class="col-8">
+                        <label class="col-6">Main fuse</label>
+                        <div class="col-6">
                             <select class="form-control" name="fuseSize">
                                 <option value="" ${config.fuseSize0}></option>
                                 <option value="25" ${config.fuseSize25}>25A</option>
diff --git a/web/index.html b/web/index.html
index ba7f56d2..69c2edad 100644
--- a/web/index.html
+++ b/web/index.html
@@ -68,10 +68,10 @@
             <a href="https://github.com/gskjold/AmsToMqttBridge/releases" class="btn btn-outline-secondary">Release notes</a>
         </div>
         <div class="col-6 text-right">
-            <a href="/configuration" class="btn btn-primary">Configuration</a>
+            <a href="configuration" class="btn btn-primary">Configuration</a>
         </div>
     </div>
 </main>
-<script src="/index.js"></script>
+<script src="index.js"></script>
 </body>
 </html>