diff --git a/bundles/org.openhab.core/src/main/java/org/openhab/core/internal/i18n/I18nProviderImpl.java b/bundles/org.openhab.core/src/main/java/org/openhab/core/internal/i18n/I18nProviderImpl.java
index ce61377b7..98510e9e8 100644
--- a/bundles/org.openhab.core/src/main/java/org/openhab/core/internal/i18n/I18nProviderImpl.java
+++ b/bundles/org.openhab.core/src/main/java/org/openhab/core/internal/i18n/I18nProviderImpl.java
@@ -77,6 +77,7 @@ import org.openhab.core.library.dimension.ElectricConductivity;
 import org.openhab.core.library.dimension.EmissionIntensity;
 import org.openhab.core.library.dimension.EnergyPrice;
 import org.openhab.core.library.dimension.Intensity;
+import org.openhab.core.library.dimension.RadiantExposure;
 import org.openhab.core.library.dimension.RadiationSpecificActivity;
 import org.openhab.core.library.dimension.VolumetricFlowRate;
 import org.openhab.core.library.types.PointType;
@@ -429,6 +430,7 @@ public class I18nProviderImpl
         addDefaultUnit(dimensionMap, RadiationDoseAbsorbed.class, Units.GRAY);
         addDefaultUnit(dimensionMap, RadiationDoseEffective.class, Units.SIEVERT);
         addDefaultUnit(dimensionMap, RadiationSpecificActivity.class, Units.BECQUEREL_PER_CUBIC_METRE);
+        addDefaultUnit(dimensionMap, RadiantExposure.class, Units.JOULE_PER_SQUARE_METRE);
         addDefaultUnit(dimensionMap, Radioactivity.class, Units.BECQUEREL);
         addDefaultUnit(dimensionMap, SolidAngle.class, Units.STERADIAN);
         addDefaultUnit(dimensionMap, Speed.class, SIUnits.KILOMETRE_PER_HOUR, ImperialUnits.MILES_PER_HOUR);
diff --git a/bundles/org.openhab.core/src/main/java/org/openhab/core/library/dimension/RadiantExposure.java b/bundles/org.openhab.core/src/main/java/org/openhab/core/library/dimension/RadiantExposure.java
new file mode 100644
index 000000000..d0ef542a4
--- /dev/null
+++ b/bundles/org.openhab.core/src/main/java/org/openhab/core/library/dimension/RadiantExposure.java
@@ -0,0 +1,27 @@
+/**
+ * Copyright (c) 2010-2024 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.openhab.core.library.dimension;
+
+import javax.measure.Quantity;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+
+/**
+ * The {@link RadiantExposure} defines the dimension for Radiant Exposure
+ * https://en.wikipedia.org/wiki/Radiant_exposure
+ *
+ * @author Gaël L'hopital - Initial contribution
+ */
+@NonNullByDefault
+public interface RadiantExposure extends Quantity<RadiantExposure> {
+}
diff --git a/bundles/org.openhab.core/src/main/java/org/openhab/core/library/unit/ImperialUnits.java b/bundles/org.openhab.core/src/main/java/org/openhab/core/library/unit/ImperialUnits.java
index 7fa660b57..1ed5614ee 100644
--- a/bundles/org.openhab.core/src/main/java/org/openhab/core/library/unit/ImperialUnits.java
+++ b/bundles/org.openhab.core/src/main/java/org/openhab/core/library/unit/ImperialUnits.java
@@ -25,6 +25,7 @@ import javax.measure.quantity.Volume;
 import javax.measure.spi.SystemOfUnits;
 
 import org.eclipse.jdt.annotation.NonNullByDefault;
+import org.openhab.core.library.dimension.Density;
 import org.openhab.core.library.dimension.VolumetricFlowRate;
 
 import tech.units.indriya.format.SimpleUnitFormat;
@@ -48,6 +49,8 @@ public final class ImperialUnits extends CustomUnits {
 
     public static final Unit<Mass> POUND = addUnit(new TransformedUnit<>("lb", Units.GRAM,
             MultiplyConverter.ofRational(BigInteger.valueOf(45359237), BigInteger.valueOf(100000))));
+    public static final Unit<Mass> GRAIN = addUnit(
+            new TransformedUnit<>("gr", Units.GRAM, MultiplyConverter.of(0.06479891)));
     /** Additionally defined units to be used in openHAB **/
     public static final Unit<Pressure> INCH_OF_MERCURY = addUnit(new TransformedUnit<>("inHg", Units.PASCAL,
             MultiplyConverter.ofRational(BigInteger.valueOf(3386388), BigInteger.valueOf(1000))));
@@ -94,6 +97,8 @@ public final class ImperialUnits extends CustomUnits {
     public static final Unit<VolumetricFlowRate> GALLON_PER_MINUTE = addUnit(
             new ProductUnit<>(GALLON_LIQUID_US.divide(tech.units.indriya.unit.Units.MINUTE)));
 
+    public static final Unit<Density> GRAIN_PER_CUBICFOOT = addUnit(new ProductUnit<>(GRAIN.divide(CUBIC_FOOT)));
+
     /*
      * Add unit symbols for imperial units.
      */
@@ -111,6 +116,7 @@ public final class ImperialUnits extends CustomUnits {
         SimpleUnitFormat.getInstance().label(GALLON_LIQUID_US, GALLON_LIQUID_US.getSymbol());
         SimpleUnitFormat.getInstance().label(GALLON_PER_MINUTE, "gal/min");
         SimpleUnitFormat.getInstance().label(POUND_FORCE_SQUARE_INCH, POUND_FORCE_SQUARE_INCH.getSymbol());
+        SimpleUnitFormat.getInstance().label(GRAIN, GRAIN.getSymbol());
     }
 
     private ImperialUnits() {
diff --git a/bundles/org.openhab.core/src/main/java/org/openhab/core/library/unit/Units.java b/bundles/org.openhab.core/src/main/java/org/openhab/core/library/unit/Units.java
index f3e220fb1..f36b25d1b 100644
--- a/bundles/org.openhab.core/src/main/java/org/openhab/core/library/unit/Units.java
+++ b/bundles/org.openhab.core/src/main/java/org/openhab/core/library/unit/Units.java
@@ -57,6 +57,7 @@ import org.openhab.core.library.dimension.Density;
 import org.openhab.core.library.dimension.ElectricConductivity;
 import org.openhab.core.library.dimension.EmissionIntensity;
 import org.openhab.core.library.dimension.Intensity;
+import org.openhab.core.library.dimension.RadiantExposure;
 import org.openhab.core.library.dimension.RadiationSpecificActivity;
 import org.openhab.core.library.dimension.VolumetricFlowRate;
 
@@ -91,13 +92,15 @@ public final class Units extends CustomUnits {
     public static final Unit<AmountOfSubstance> MOLE = addUnit(tech.units.indriya.unit.Units.MOLE);
     public static final Unit<Volume> LITRE = addUnit(tech.units.indriya.unit.Units.LITRE);
     @SuppressWarnings("unchecked")
-    public static final Unit<AmountOfSubstance> DEUTSCHE_HAERTE = addUnit(new TransformedUnit<>("°dH",
-            (Unit<AmountOfSubstance>) MetricPrefix.MILLI(Units.MOLE).divide(Units.LITRE), MultiplyConverter.of(5.6)));
+    public static final Unit<Dimensionless> DEUTSCHE_HAERTE = addUnit((Unit<Dimensionless>) new TransformedUnit<>("°dH",
+            MetricPrefix.MILLI(Units.MOLE).divide(Units.LITRE), MultiplyConverter.of(0.17833)));
     public static final Unit<Angle> DEGREE_ANGLE = addUnit(NonSI.DEGREE_ANGLE);
     public static final Unit<Angle> RADIAN = addUnit(tech.units.indriya.unit.Units.RADIAN);
     public static final Unit<ArealDensity> DOBSON_UNIT = addUnit(
             new ProductUnit<>(MetricPrefix.MILLI(tech.units.indriya.unit.Units.MOLE).multiply(0.4462)
                     .divide(tech.units.indriya.unit.Units.SQUARE_METRE)));
+    public static final Unit<ArealDensity> KILOGRAM_PER_SQUARE_METRE = addUnit(new ProductUnit<>(
+            tech.units.indriya.unit.Units.KILOGRAM.divide(tech.units.indriya.unit.Units.SQUARE_METRE)));
     public static final Unit<CatalyticActivity> KATAL = addUnit(tech.units.indriya.unit.Units.KATAL);
     public static final Unit<Density> KILOGRAM_PER_CUBICMETRE = addUnit(new ProductUnit<>(
             tech.units.indriya.unit.Units.KILOGRAM.divide(tech.units.indriya.unit.Units.CUBIC_METRE)));
@@ -187,6 +190,10 @@ public final class Units extends CustomUnits {
             new TransformedUnit<>("kn", tech.units.indriya.unit.Units.KILOMETRE_PER_HOUR,
                     MultiplyConverter.ofRational(BigInteger.valueOf(1852), BigInteger.valueOf(1000))));
     public static final Unit<SolidAngle> STERADIAN = addUnit(tech.units.indriya.unit.Units.STERADIAN);
+    public static final Unit<RadiantExposure> WATT_HOUR_PER_SQUARE_METRE = addUnit(
+            new ProductUnit<>(WATT_HOUR.divide(tech.units.indriya.unit.Units.SQUARE_METRE)));
+    public static final Unit<RadiantExposure> JOULE_PER_SQUARE_METRE = addUnit(
+            new ProductUnit<>(JOULE.divide(tech.units.indriya.unit.Units.SQUARE_METRE)));
     public static final Unit<Temperature> KELVIN = addUnit(tech.units.indriya.unit.Units.KELVIN);
     public static final Unit<?> MIRED = addUnit(MetricPrefix.MEGA(tech.units.indriya.unit.Units.KELVIN).inverse());
     public static final Unit<Time> SECOND = addUnit(tech.units.indriya.unit.Units.SECOND);
@@ -262,7 +269,7 @@ public final class Units extends CustomUnits {
         SimpleUnitFormat.getInstance().label(DECIBEL, "dB");
         SimpleUnitFormat.getInstance().label(DECIBEL_MILLIWATTS, "dBm");
         SimpleUnitFormat.getInstance().label(DEGREE_ANGLE, "°");
-        SimpleUnitFormat.getInstance().label(DEUTSCHE_HAERTE, "°dH");
+        SimpleUnitFormat.getInstance().label(DEUTSCHE_HAERTE, DEUTSCHE_HAERTE.getSymbol());
         SimpleUnitFormat.getInstance().label(DOBSON_UNIT, "DU");
         SimpleUnitFormat.getInstance().label(GRAM_PER_KILOWATT_HOUR, "g/kWh");
         SimpleUnitFormat.getInstance().label(GIGABYTE, "GB");
@@ -276,6 +283,7 @@ public final class Units extends CustomUnits {
         SimpleUnitFormat.getInstance().alias(KIBIBYTE, "kio");
         SimpleUnitFormat.getInstance().label(KILOBIT, "kbit");
         SimpleUnitFormat.getInstance().label(KILOBIT_PER_SECOND, "kbit/s");
+        SimpleUnitFormat.getInstance().label(KILOGRAM_PER_SQUARE_METRE, "kg/m²");
         SimpleUnitFormat.getInstance().label(KILOVAR, "kvar");
         SimpleUnitFormat.getInstance().label(KILOVAR_HOUR, "kvarh");
         SimpleUnitFormat.getInstance().label(KILOVOLT_AMPERE, "kVA");
@@ -315,6 +323,7 @@ public final class Units extends CustomUnits {
         SimpleUnitFormat.getInstance().label(VOLT_AMPERE, "VA");
         SimpleUnitFormat.getInstance().label(VOLT_AMPERE_HOUR, "VAh");
         SimpleUnitFormat.getInstance().label(WATT_HOUR, "Wh");
+        SimpleUnitFormat.getInstance().label(WATT_HOUR_PER_SQUARE_METRE, "Wh/m²");
         SimpleUnitFormat.getInstance().label(WATT_SECOND, "Ws");
 
         // workarounds for https://github.com/unitsofmeasurement/indriya/issues/409
diff --git a/bundles/org.openhab.core/src/test/java/org/openhab/core/library/unit/UnitsTest.java b/bundles/org.openhab.core/src/test/java/org/openhab/core/library/unit/UnitsTest.java
index f88cb2a6b..79932361a 100644
--- a/bundles/org.openhab.core/src/test/java/org/openhab/core/library/unit/UnitsTest.java
+++ b/bundles/org.openhab.core/src/test/java/org/openhab/core/library/unit/UnitsTest.java
@@ -15,7 +15,7 @@ package org.openhab.core.library.unit;
 import static org.hamcrest.CoreMatchers.*;
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.number.IsCloseTo.closeTo;
-import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.*;
 
 import java.math.BigDecimal;
 
@@ -38,6 +38,7 @@ import org.openhab.core.library.dimension.ArealDensity;
 import org.openhab.core.library.dimension.Density;
 import org.openhab.core.library.dimension.Intensity;
 import org.openhab.core.library.types.QuantityType;
+import org.openhab.core.types.util.UnitUtils;
 
 import tech.units.indriya.quantity.Quantities;
 
@@ -442,6 +443,44 @@ public class UnitsTest {
         assertEquals(Units.MIRED, value.getUnit());
     }
 
+    public void testGrains() {
+        assertThat(ImperialUnits.GRAIN.getSymbol(), is("gr"));
+        QuantityType<?> oneHundredGrains = QuantityType.valueOf("100 gr");
+        QuantityType<?> converted = oneHundredGrains.toUnit("g");
+        assertThat(converted.doubleValue(), is(closeTo(6.479891, DEFAULT_ERROR)));
+        assertThat(ImperialUnits.GRAIN_PER_CUBICFOOT.toString(), is("gr/ft³"));
+        QuantityType<?> grainDensity = QuantityType.valueOf("20 gr/ft³");
+        QuantityType<?> convertedDensity = grainDensity.toUnit(Units.MICROGRAM_PER_CUBICMETRE);
+        assertThat(convertedDensity.doubleValue(), is(closeTo(45767038.211314686, DEFAULT_ERROR)));
+    }
+
+    @Test
+    public void testArealDensity() {
+        QuantityType<?> newspaper = QuantityType.valueOf("72 g/m²");
+        QuantityType<?> converted = newspaper.toUnit(Units.KILOGRAM_PER_SQUARE_METRE);
+        assertEquals(converted.doubleValue(), 0.072);
+    }
+
+    @Test
+    public void testAmountOfSubstance() {
+        QuantityType<?> mmolpl = QuantityType.valueOf("0.17833 mmol/l");
+        String mmolplDimension = UnitUtils.getDimensionName(mmolpl.getUnit());
+        QuantityType<?> dh = QuantityType.valueOf("1 °dH");
+        String hDimension = UnitUtils.getDimensionName(dh.getUnit());
+        assertTrue(hDimension.equals(mmolplDimension));
+        assertTrue("Dimensionless".equalsIgnoreCase(hDimension));
+        QuantityType<?> converted = dh.toUnit("mmol/l");
+        assertThat(converted.doubleValue(), is(closeTo(mmolpl.doubleValue(), DEFAULT_ERROR)));
+    }
+
+    @Test
+    public void testSolarIrradiation() {
+        QuantityType<?> whpsm2 = QuantityType.valueOf(10, Units.WATT_HOUR_PER_SQUARE_METRE);
+        assertThat(whpsm2.getUnit().toString(), is("Wh/m²"));
+        QuantityType<?> jpsm2 = QuantityType.valueOf(10, Units.JOULE_PER_SQUARE_METRE);
+        assertThat(jpsm2.getUnit().toString(), is("J/m²"));
+    }
+
     private static class QuantityEquals extends IsEqual<Quantity<?>> {
         private Quantity<?> quantity;