diff --git a/src/asset.rs b/src/asset.rs
index 489c29c0a..c115ee646 100644
--- a/src/asset.rs
+++ b/src/asset.rs
@@ -650,7 +650,7 @@ impl Asset {
                 flow.coeff
                     * prices
                         .get(&flow.commodity.id, &self.region_id, time_slice)
-                        .unwrap_or_default()
+                        .unwrap_or(MoneyPerFlow(0.0))
             })
             .sum()
     }
diff --git a/src/input/asset.rs b/src/input/asset.rs
index 8f219b3f6..c29c7b962 100644
--- a/src/input/asset.rs
+++ b/src/input/asset.rs
@@ -17,7 +17,7 @@ use std::rc::Rc;
 
 const ASSETS_FILE_NAME: &str = "assets.csv";
 
-#[derive(Default, Deserialize, PartialEq)]
+#[derive(Deserialize, PartialEq)]
 struct AssetRaw {
     process_id: String,
     region_id: String,
diff --git a/src/simulation/investment/appraisal.rs b/src/simulation/investment/appraisal.rs
index bf33739e7..906bff3cb 100644
--- a/src/simulation/investment/appraisal.rs
+++ b/src/simulation/investment/appraisal.rs
@@ -363,7 +363,7 @@ mod tests {
     use crate::fixture::{agent_id, asset, process, region_id};
     use crate::process::Process;
     use crate::region::RegionID;
-    use crate::units::{Money, MoneyPerActivity};
+    use crate::units::{Money, MoneyPerActivity, MoneyPerFlow};
     use float_cmp::assert_approx_eq;
     use rstest::rstest;
     use std::rc::Rc;
@@ -551,7 +551,11 @@ mod tests {
             .map(|(asset, metric)| AppraisalOutput {
                 asset: AssetRef::from(asset),
                 capacity: AssetCapacity::Continuous(Capacity(10.0)),
-                coefficients: ObjectiveCoefficients::default(),
+                coefficients: ObjectiveCoefficients {
+                    capacity_coefficient: MoneyPerCapacity(0.0),
+                    activity_coefficients: IndexMap::new(),
+                    unmet_demand_coefficient: MoneyPerFlow(0.0),
+                },
                 activity: IndexMap::new(),
                 demand: IndexMap::new(),
                 unmet_demand: IndexMap::new(),
@@ -877,7 +881,11 @@ mod tests {
             .map(|metric| AppraisalOutput {
                 asset: AssetRef::from(asset.clone()),
                 capacity: AssetCapacity::Continuous(Capacity(0.0)),
-                coefficients: ObjectiveCoefficients::default(),
+                coefficients: ObjectiveCoefficients {
+                    capacity_coefficient: MoneyPerCapacity(0.0),
+                    activity_coefficients: IndexMap::new(),
+                    unmet_demand_coefficient: MoneyPerFlow(0.0),
+                },
                 activity: IndexMap::new(),
                 demand: IndexMap::new(),
                 unmet_demand: IndexMap::new(),
diff --git a/src/simulation/investment/appraisal/coefficients.rs b/src/simulation/investment/appraisal/coefficients.rs
index e09511e5d..0c17f2b74 100644
--- a/src/simulation/investment/appraisal/coefficients.rs
+++ b/src/simulation/investment/appraisal/coefficients.rs
@@ -15,7 +15,6 @@ use std::collections::HashMap;
 /// the investment appraisal routines. The map contains the per-capacity and per-activity cost
 /// coefficients used in the appraisal optimisation, together with the unmet-demand penalty.
 #[derive(Clone)]
-#[cfg_attr(test, derive(Default))]
 pub struct ObjectiveCoefficients {
     /// Cost per unit of capacity
     pub capacity_coefficient: MoneyPerCapacity,
diff --git a/src/simulation/optimisation.rs b/src/simulation/optimisation.rs
index 0ddaf8be7..c86638224 100644
--- a/src/simulation/optimisation.rs
+++ b/src/simulation/optimisation.rs
@@ -795,10 +795,11 @@ fn calculate_activity_coefficient(
     input_prices: Option<&CommodityPrices>,
 ) -> MoneyPerActivity {
     let opex = asset.get_operating_cost(year, time_slice);
-    let input_cost = input_prices
-        .map(|prices| asset.get_input_cost_from_prices(prices, time_slice))
-        .unwrap_or_default();
-    opex + input_cost
+    if let Some(prices) = input_prices {
+        opex + asset.get_input_cost_from_prices(prices, time_slice)
+    } else {
+        opex
+    }
 }
 
 /// Calculate the cost coefficient for a capacity variable (for flexible capacity assets only).
diff --git a/src/simulation/prices.rs b/src/simulation/prices.rs
index dfb1b7e47..1242ef18d 100644
--- a/src/simulation/prices.rs
+++ b/src/simulation/prices.rs
@@ -180,7 +180,10 @@ impl CommodityPrices {
             // NB: Time slice fractions will sum to one
             let weight = time_slice_info.time_slices[time_slice_id] / Year(1.0);
             let key = (commodity_id.clone(), region_id.clone());
-            *weighted_prices.entry(key).or_default() += *price * weight;
+            weighted_prices
+                .entry(key)
+                .and_modify(|v| *v += *price * weight)
+                .or_insert_with(|| *price * weight);
         }
 
         weighted_prices
@@ -352,7 +355,7 @@ where
 ///
 /// Note: this should be similar to the "shadow price" strategy, which is also based on marginal
 /// costs of the most expensive producer, but may be more successful in cases where there are
-//  multiple SED/SVD outputs per asset.
+/// multiple SED/SVD outputs per asset.
 ///
 /// # Arguments
 ///
diff --git a/src/units.rs b/src/units.rs
index 437db54c7..2c40554f6 100644
--- a/src/units.rs
+++ b/src/units.rs
@@ -22,7 +22,6 @@ pub trait UnitType:
     + Sum
     + ApproxEq<Margin = F64Margin>
     + fmt::Display
-    + Default
 {
     /// Create from an f64 value
     fn new(value: f64) -> Self;
@@ -51,7 +50,6 @@ macro_rules! base_unit_struct {
             Copy,
             PartialEq,
             PartialOrd,
-            Default,
             Serialize,
             derive_more::Add,
             derive_more::Sub,